Retaining Walls

On hillside properties across Pacific Palisades, Bel Air, Malibu, Beverly Hills, and the greater Westside, retaining walls are one of the most consequential and most misunderstood elements of residential construction. They are structural systems, not landscape features. On a typical hillside project in the Santa Monica Mountains or Hollywood Hills, retaining walls frequently represent $200,000 to $800,000 or more of total project cost, and the engineering decisions behind them affect everything from foundation design to drainage to neighbor relations to project timeline. Most owners encounter retaining walls as a surprise, either during due diligence on a new purchase, during the design phase of a new home, or when an existing wall starts showing signs of distress. This page explains what is actually involved.

Last updated: February 2026

What Retaining Walls Actually Do

A retaining wall resists lateral earth pressure. It holds back soil that would otherwise move downhill under the force of gravity. That is its purpose. Everything else - the appearance, the terracing, the usable pad area it creates - is secondary to that structural function.

The distinction matters because it separates retaining walls from every other wall on a property. A 4-foot decorative garden wall built from stacked stone to create a planter bed is a landscape element. An older 16-foot cast-in-place reinforced concrete wall holding back 20 feet of hillside with a house sitting on top of it is a structural system that must resist tens of thousands of pounds of lateral force per linear foot, including additional forces during an earthquake. These two walls share a name and almost nothing else. The engineering is different, the code requirements are different, the permitting is different, and the cost universe is different by an order of magnitude.

Los Angeles has more retaining walls per mile of residential street than almost anywhere else in the country. The geography of the Santa Monica Mountains, Hollywood Hills, and the coastal canyons running through Pacific Palisades and Malibu creates conditions where nearly every buildable lot requires some form of earth retention. The lots are steep. The geology is complex, with layers of sandstone, shale, and alluvium that behave differently under load and in the presence of water. The seismic environment is active. And the density of development means that one property's retaining wall is often the structural boundary condition for the adjacent property's stability.

The types of retaining walls used in LA residential construction fall into several categories, each suited to different site conditions. Cantilever walls, the workhorse of LA hillside construction, use a reinforced concrete footing and stem to resist overturning through structural leverage, and can be formed and poured in place or constructed using shotcrete applied over reinforcement. Many hillside retaining walls are supported on deep foundations, with drilled piles (caissons) connected by grade beams forming the structural system that transfers lateral and vertical loads into competent bearing material below the surface soils. Typical residential caissons are 18 to 36 inches in diameter, drilled 2 to 5 feet into bedrock at depths that can reach 30 to 60 feet on steep hillside sites. The grade beams spanning between caissons distribute forces along the wall's length and provide the bearing surface for the wall stem. Rebar cages are tied on site - on hillside streets, transporting pre-assembled cages is typically impractical - then lowered into the drilled shaft by crane before concrete placement. Our foundation systems page covers caisson and grade beam construction in full detail, including drilling operations, concrete placement methods, groundwater complications, and cost ranges.

This pile-and-grade-beam configuration is the conventional foundation system for most hillside walls and requires careful construction logistics planning. The drill rig needs a level working surface to operate safely and drill plumb holes. On sloped sites, this means cutting a temporary drilling bench - a level pad graded into the hillside, typically 10 to 12 feet wide - for the rig to sit on. A drilling bench is essentially a temporary road or platform, built up or cut in by a grader, and often serves double duty as a staging area for excavated soil before it is hauled off or redistributed on site. On steep sites, multiple benches at different elevations may be required to reach all pile locations, and each bench requires its own grading, access, and restoration after drilling is complete. The constructability question on every hillside retaining wall project is whether the site can accommodate the benches needed for the drill rig that can achieve the required pile diameters and depths. Rig selection, bench locations, and access routes are among the first things a construction manager evaluates during preconstruction site walks.

Soldier pile and lagging walls use steel beams drilled into the ground with horizontal members spanning between them, often supplemented with tiebacks anchored into stable soil or rock behind the wall. Mechanically stabilized earth walls use layers of reinforced fill to create a stable mass. Gravity walls rely on their own mass to resist lateral forces and are limited to shorter heights.

Hillside properties throughout LA also contain a range of non-code-compliant retaining structures that are not engineered walls at all: pipe-and-board assemblies, stacked railroad ties, timber cribbing, and other improvised structures that were installed without engineering, without permits, and without drainage. These are not retaining walls in any structural sense. They provide some short-term soil retention, but they are not designed for the lateral loads they carry, they deteriorate over time, and they are routinely discovered during due diligence or renovation work. Identifying these structures early and understanding the cost to replace them with engineered systems is a critical preconstruction task.

Which system gets used on any given project depends on the height of the wall, the soil conditions, the loading above and below the wall, the available space for construction, and the access constraints of the site. On many hillside projects, multiple wall systems are used on the same property because the conditions change from one side of the lot to the other.

Why Retaining Walls Fail

The single most common cause of retaining wall failure in Los Angeles is water. Specifically, hydrostatic pressure from inadequate drainage behind the wall.

Every retaining wall is designed to resist a specific set of forces: the lateral earth pressure from the retained soil, any surcharge loading from structures or equipment above the wall, and seismic forces. What the wall is generally not designed to resist is the additional pressure created when water saturates the soil behind it and cannot drain away. When drainage fails, hydrostatic pressure can increase the total lateral force on the wall by 40 to 60 percent or more - a loading condition most walls were never sized for. The mechanics of how this works are explained in the forces section below.

Surface water management is equally critical and frequently overlooked. The swale at the top of a slope, the area drain behind the wall, the downspout connection that routes roof water away from the retained soil - these may look unnecessary in dry weather, but their absence during a rain event can saturate the soil behind a wall in hours. Proper surface water diversion is the first line of defense; the subdrain behind the wall is the second. Both must function together.

Pre-code walls are a related and widespread problem. Many retaining walls in LA's hillside neighborhoods were built before modern grading and building code requirements were established. Walls built before the city's 1963 grading ordinance are particularly concerning because they may have been constructed without engineering, without inspection, without adequate reinforcement, and without drainage systems. A significant number of walls in older hillside neighborhoods in Bel Air, the Bird Streets, and parts of the Palisades fall into this category. Finding out what is behind an old wall, or more accurately, what is not behind it, is one of the most common and most consequential discoveries during hillside renovation projects.

Other failure modes we see regularly on LA residential properties include undermining from erosion at the base of the wall, particularly on canyon properties where surface water concentrates during storms. Surcharge loading that exceeds the original design capacity, which happens when a subsequent owner adds a structure, pool, or significant hardscape above the wall without evaluating the impact on the wall's design assumptions. Soil creep, the slow downhill movement of surface soils on steep slopes, which places lateral forces on walls that accumulate over decades. And seismic movement, which can cause sudden displacement or progressive cracking in walls that were not designed for current seismic loading requirements.

Signs of Failure

The signs of failure are not subtle once you know what to look for. Horizontal cracking along the face of the wall, particularly at mid-height, indicates the wall is bending under lateral pressure beyond its capacity. Leaning or tilting at the top of the wall, even by a few inches, indicates the wall is rotating and the footing may be failing. Bulging at the base suggests the wall is being pushed outward by pressure it cannot resist. Separation from adjacent structures indicates differential movement. Water emerging from the face of the wall at locations other than designed weep holes indicates the drainage system is overwhelmed or absent. Soil movement at the top of the wall, visible as cracking in the ground surface, separating pavement, or tilting fences, indicates the retained soil is beginning to move.

Any of these signs on a hillside property in Los Angeles warrants immediate evaluation by a structural engineer. Retaining wall failures can progress from visible distress to catastrophic collapse quickly, particularly during rain events.

Retaining Wall Types Used in LA Residential Construction

This section describes the wall systems that actually get built on residential hillside sites in the Los Angeles market. Not a textbook list of every retaining wall type that exists, but a practitioner's account of what we encounter, specify, and build on real projects.

Cast-in-Place Reinforced Concrete Cantilever Walls

This is the workhorse of LA residential retaining wall construction. A cantilever wall consists of a reinforced concrete stem rising from a reinforced concrete spread footing. The footing extends behind the wall (under the retained soil) so that the weight of the soil sitting on top of the footing's heel resists the overturning force. The stem is reinforced with vertical and horizontal rebar to resist bending and shear.

For residential applications in LA, cantilever walls are commonly built from 4 feet up to approximately 15 or 16 feet in exposed height, though engineered designs can go higher. The relationship between wall height and footing width is roughly proportional: a 10-foot wall typically requires a footing 6 to 8 feet wide, depending on soil conditions and surcharge loading. A 15-foot wall may require a footing 9 to 12 feet wide. That footing width matters enormously on constrained hillside lots where every foot of horizontal space is contested between the house footprint, setbacks, and retaining wall footings.

Cantilever walls are built in place, which means they require rebar installation, formwork on both sides of the stem, concrete placement, and curing time before backfill. On hillside sites with limited access, the logistics of delivering rebar and getting concrete trucks to the pour location can significantly affect both cost and schedule. Pile cages for deep foundations are often tied on site rather than delivered pre-fabricated, because the access constraints on hillside streets make transporting assembled cages impractical.

For new construction on hillside lots where the wall alignment allows adequate footing width and there is reasonable access for construction, cast-in-place cantilever walls are typically the most cost-effective structural solution. They are well understood by LA's structural engineering community, they are familiar to LADBS plan check engineers, and there is deep trade capacity in the market.

Soldier Pile and Lagging

When a cantilever wall is not feasible due to space constraints, property line conditions, or the need to retain soil during excavation adjacent to an existing structure, soldier pile and lagging is often the answer.

The system works by drilling holes at regular spacing, usually 6 to 10 feet on center, and dropping steel H-piles (typically W-flange sections) into the holes. The lower portion of each pile is concreted in place, embedding the pile in stable soil or bedrock. A portion of the upper pile is typically slurried with a lean concrete mix that can be chipped back later to install the lagging. Once the piles are in place, excavation proceeds from the top down. As each lift is excavated, the slurried concrete is chipped away from between the pile flanges and horizontal lagging (timber, concrete, or shotcrete) is installed between the piles to retain the soil. For walls that require additional lateral support, tiebacks are drilled behind the wall at an angle, typically 15 to 30 degrees below horizontal, and anchored into stable material behind the active failure plane. Each tieback is tensioned and load-tested before being locked off.

Soldier pile and lagging is the standard approach for deep excavations adjacent to property lines in LA's hillside neighborhoods. When the adjacent property is at a higher elevation and the footing of a cantilever wall would extend under the neighbor's property, soldier pile and lagging can be installed entirely within the property line because the piles go straight down. Tiebacks installed behind the wall provide additional lateral support and are anchored into stable material at depth. In LA residential hillside construction, tiebacks through the wall face are less common than in heavy civil applications, though the engineering principles are the same. Tiebacks are a distinct structural system from slope stabilization using soil nails and surface netting, which address different geotechnical conditions.

There is a critical caveat with tiebacks: they extend laterally into the ground, and on hillside lots, they frequently extend under the adjacent property. This requires a tieback easement from the neighboring property owner. Getting that easement can take weeks or months, involves legal documentation, and sometimes requires compensation. In some cases, the neighbor refuses the easement entirely, which forces a redesign to a cantilevered soldier pile system (deeper embedment, larger piles, closer spacing) or a different wall system altogether. We have seen projects where the tieback easement negotiation took longer than the wall construction itself. This is one of the most important items to identify and address early in preconstruction.

Soil Nail Walls

Soil nail walls are an alternative to soldier pile systems that can be effective in the right conditions. The method works top-down: as each lift of excavation proceeds (typically 4 to 5 feet at a time), steel bars are drilled into the exposed soil face at a slight downward angle and grouted in place. A layer of reinforced shotcrete is then applied over the face. The process repeats with each lift of excavation until the full wall height is reached.

The advantage of soil nailing is that it avoids the cost of pre-drilling large-diameter soldier piles and avoids the need for tieback easements since the nails extend into the soil behind the wall on the same property. Installation is faster because you do not need the large drill rigs required for pile installation. Whether soil nailing is more cost-effective than soldier piles depends on the scenario: for straightforward cuts in competent native soil, soil nailing can offer significant savings. For complex cuts with challenging access, variable soil conditions, or proximity to structures, soldier piles may be the better system. Soil nail walls work well in competent native soil, which is common across much of the hillside geology in the Palisades, Bel Air, and Beverly Hills where you encounter sandstone, siltstone, and dense formational materials.

The limitations are equally important. Soil nailing does not work well in loose fill, highly plastic clays, or saturated soils where the nails cannot develop adequate pullout resistance. It requires that the soil stand unsupported for a short time during each excavation lift, which is not feasible in very loose or granular material. On residential hillside sites, the geotechnical engineer determines whether soil conditions support the use of soil nails.

A soil nail wall can serve as either temporary shoring or a permanent retaining system. When used as a permanent system, the shotcrete face can receive various architectural finishes, veneer stone, or modular block facing, though these decorative applications are more common in commercial and civil work than in residential hillside construction. Some specialty engineers use proprietary driven-nail systems that are even faster and more economical than conventionally drilled soil nails.

Shotcrete Walls

Shotcrete is concrete applied pneumatically at high velocity onto a prepared surface. In retaining wall applications on hillside sites, shotcrete is commonly used where conventional forming is impractical due to slope geometry or access constraints. Most shotcrete retaining walls are still structurally cantilevered - the engineering is the same as a formed-and-poured cantilever wall, but the concrete placement method is different. The typical process involves excavating or trimming the slope to the design profile, installing reinforcing steel (rebar and welded wire fabric) against the exposed soil face, and then shooting concrete onto the reinforcement.

Shotcrete retaining walls are common on steep cut slopes in the Palisades, Malibu canyons, and the hillside streets above Sunset. They conform to irregular slope surfaces more readily than formed walls. The finished shotcrete face is typically plastered for a clean appearance on the exposed side, though on walls that will be concealed by landscaping, the rough finish may be left as-is.

Shotcrete requires licensed nozzlemen operating under the supervision of an ACI-certified shotcrete nozzleman program. Before production work begins, a test panel must be shot, cored, and certified by the deputy inspector to verify the mix achieves the specified compressive strength and density. During application, rebound - the material that bounces off the reinforcement and does not bond - must be cleaned up and removed by the concrete crew. Rebound cannot be left in place or incorporated into the wall because it lacks structural integrity. Poor shotcrete work, with excessive rebound, dry spots, or voids behind the rebar, creates a wall that looks solid on the surface but lacks structural integrity. This is an area where construction oversight matters significantly.

Gravity Walls

Gravity walls resist lateral earth pressure through their own mass. In residential applications, gravity walls are built from masonry block, stone, or mass concrete. They are inherently limited in height because the required mass increases rapidly with wall height. For structural applications on hillside sites, gravity walls are generally practical only up to about 4 to 6 feet.

Gravity walls show up on LA residential properties primarily as older walls that were built decades ago, often without engineering, and as newer landscape-scale walls that do not require permits (under 4 feet from footing to top, with no surcharge). Gravity walls are also commonly used surrounding tree pockets where engineered wall systems cannot be constructed within the protected root zone, and in situations where the site conditions or zoning constraints may not allow for a conventional engineered retaining wall. For the structural retaining wall applications that are the focus of this page, gravity walls have limited use in current practice, with one important exception discussed below.

Garden Walls and Low Retaining Walls

Walls under 4 feet in height, measured from the bottom of the footing to the top of the wall, that do not support a surcharge are exempt from building permit requirements under LAMC Section 91.106.3.2. This is the threshold that allows short landscape retaining walls, planter walls, and garden terracing to be built without engineering or permits.

Even though a permit-exempt garden wall does not require structural engineering, it is still subject to the zoning code. In required yards (setback areas), LAMC Section 12.22C20(f) governs wall heights, which typically limits walls in front yards to 3.5 feet. Additionally, under Ordinance 176,445, permit-exempt walls are specifically excluded from the retaining wall count. This means you can build a 3.5-foot garden wall in addition to the one 12-foot wall (or two 10-foot walls) allowed by the ordinance. That distinction matters for site planning on hillside properties where every foot of grade change requires retention.

For owners considering low walls, the practical guidance is straightforward: walls under 4 feet retaining earth with no structure, driveway, pool, or other load above them can be built without permits. Add a surcharge, and permits are required regardless of height. And while the wall may not need engineering, it still needs drainage. Even a 3-foot wall with no drain behind it will fail when the soil saturates.

Tree Pockets and Retaining Walls Around Protected Trees

On hillside lots throughout Bel Air, the Palisades, and Beverly Hills, mature oaks, sycamores, and other protected species are commonly planted into the slope, and the grade around them has been retained over decades by walls of varying quality. When those walls fail, or when new construction requires grade changes near these trees, the conflict between retaining wall engineering and tree preservation becomes one of the hardest problems in hillside construction.

The practical workaround that the industry has settled on is the dry-stacked boulder gravity wall. Boulders sit on grade without footing excavation. They do not introduce concrete or alter soil chemistry. They are porous, allowing water and air to continue reaching the root zone. If kept under 4 feet in height, they require no building permit, which means no plan check review that would flag the proximity to a protected tree. Responsible contractors coordinate with a certified arborist to position boulders with minimal root disturbance, often placing them by hand or with a rubber-tracked mini excavator rather than heavy equipment that would compact the root zone.

Railroad ties are the other common tree pocket workaround. Stacked ties can retain 2 to 4 feet of soil without footing excavation. The question is how they perform underground over time. Traditional creosote-soaked railroad ties resist rot and insect damage effectively but leach toxic compounds into the surrounding soil, which is a concern near tree root zones and any area where water runoff reaches landscaping or living spaces. Pressure-treated timber ties (typically treated with copper-based preservatives like MCA or CCA for ground contact) deteriorate faster than creosote-treated ties in direct soil contact, with a realistic service life of 10 to 15 years before significant decay sets in. Either way, railroad tie walls are not engineered structures. They are field-expedient solutions that will need to be replaced, and the replacement cost should be factored into any long-term site planning.

This is not the elegant engineered solution anyone would draw on paper. It is the field-proven approach that balances structural need with tree preservation requirements on sites where the alternative is either losing the tree (which triggers its own lengthy permit and mitigation process) or building an engineered wall that technically violates the protected tree ordinance. When we encounter tree pocket conditions on a project, we bring in the arborist during preconstruction, not after the wall design is complete.

Mechanically Stabilized Earth (MSE) Walls

MSE walls use layers of compacted fill reinforced with horizontal geogrid or geotextile strips to create a stable soil mass. The wall face is typically modular concrete blocks or precast panels. The reinforcement extends back into the fill zone, and the entire mass acts as a gravity structure.

MSE walls can be more cost-effective than cast-in-place concrete for taller walls where there is adequate space behind the wall face for the reinforced fill zone (typically 60 to 70 percent of the wall height). On hillside residential sites, that space requirement is often the limiting factor, and MSE walls are more common on larger lots, roadway-adjacent applications, and properties where the geometry allows a wide construction envelope behind the wall.

Temporary Shoring vs. Permanent Walls

This distinction causes more confusion and more budget surprises than almost any other topic in hillside construction. Temporary shoring holds soil back during construction. Permanent retaining walls hold soil back for the life of the structure. They are not the same thing, and they are not interchangeable.

On a hillside project where a basement or subterranean garage requires deep excavation adjacent to a slope or adjacent property, temporary shoring is required to support the soil during the excavation phase. This shoring may be soldier pile and lagging, sheet piling, soil nails, or another system. In coastal areas like Malibu, where high water tables and sandy soils are common, secant pile walls - interlocking drilled concrete piles that form a continuous, water-resistant barrier - may be required where conventional soldier pile systems would allow groundwater intrusion into the excavation. Once the permanent structure is built, including the permanent basement walls that will serve as the long-term retaining system, the temporary shoring has served its purpose.

The budget implication is significant. Temporary shoring on a hillside project can cost $150,000 to $500,000 or more, and that cost produces a system that gets removed or abandoned in place once the permanent structure is complete. Shoring is classified as "means and methods" - the contractor's temporary construction methodology, as distinct from the permanent design. Because it is means and methods, temporary shoring is not required to be shown on the structural engineer's drawings, even though it is a major cost item. This is one reason shoring frequently comes as a budget surprise: the architect's plans show the finished building, not the temporary systems required to build it. Having the project's structural engineer design the shoring is often the most thorough approach, but design-build shoring is also common, where specialty shoring contractors engineer and stamp their own systems through a California-licensed civil or structural engineer. Understanding whether a project requires temporary shoring, permanent retaining walls, or both, and how those costs layer, is one of the first things a construction manager evaluates during preconstruction. Our foundation systems page includes detailed shoring cost ranges by system type.

Rakers and Internal Bracing

When tiebacks are not feasible - whether because the neighbor will not grant an easement, because utilities or other obstructions exist behind the wall, or because the site geometry does not allow anchor installation - the alternative lateral support system is internal bracing using rakers or struts.

A raker is a diagonal steel brace that extends from the face of the shoring wall down to the base of the excavation. It works in compression: the lateral earth pressure pushes against the wall, the wall transfers that force into the raker, and the raker transfers it into a concrete heel block (sometimes called a kicker block) at the excavation floor. In deep excavation work, the foundation slab is typically poured first at the center of the excavation, and rakers brace against it or against purpose-built heel blocks. Rakers are typically fabricated from heavy steel wide-flange sections and are installed as the excavation progresses, with each level of rakers supporting a section of wall height. In residential hillside work, the principle is the same but the scale is smaller - rakers brace the temporary shoring while permanent retaining walls, grade beams, or basement walls are constructed.

Struts work on the same principle but run horizontally between opposing walls of an excavation, bracing each side against the other. In residential hillside construction, struts are less common than rakers because the excavation geometry is rarely symmetrical enough to use them effectively.

The engineering of raker systems requires analysis of the lateral loads, the angle of the raker (typically 30 to 45 degrees from horizontal), the axial capacity of the raker section, the connection design at both the wall and the kicker block, and the bearing capacity of the soil under the kicker. The specialty shoring engineer designs these systems.

Shared Walls and Lot-Line Issues

This is one of the most complex and least discussed topics in LA hillside construction. Adjacent hillside properties frequently share retaining walls at or near the lot line, and this creates legal, engineering, and construction challenges that consistently catch owners off guard.

Ownership and Responsibility

The threshold question with any shared retaining wall is: who owns it, and who is responsible for its maintenance? California Civil Code Section 832 establishes that each coterminous owner (that is, each owner whose property shares a common boundary with the adjacent property) is entitled to the lateral and subjacent support their land receives from the adjoining land. However, unlike the Good Neighbor Fence Act (California Civil Code Section 841), which creates a presumption of shared responsibility for boundary fences, there is no equivalent statutory presumption for retaining walls. Responsibility is determined by who caused the need for the wall, who built it, where it sits relative to the property line, and what agreements exist.

In practice, on hillside properties in Bel Air, the Palisades, and Beverly Hills, the ownership history of shared retaining walls is often unclear. Walls were built decades ago by a developer who subdivided the hillside and graded both lots. No recorded agreements exist. The wall sits on or near the property line, and both properties depend on it. When the wall begins to fail, both owners have a problem but neither has a clear obligation to pay for the fix.

Construction Coordination

When one property owner needs to excavate or build adjacent to a shared lot-line wall, the coordination challenges multiply. Under California Civil Code Section 832, a property owner intending to excavate must give reasonable notice to the adjoining owner, stating the depth of the excavation and when it will begin. If the excavation will be deeper than the adjoining property's foundations, the adjoining owner must be given at least 30 days to take protective measures.

On hillside projects, this translates to real operational complexity. The neighbor may not be rebuilding on the same timeline. The adjacent lot may have been purchased by an investor who is holding it vacant. The owner may be an estate in probate with no clear decision-maker. Each of these situations requires coordination between property owners, their respective structural engineers, and the construction activities that affect both properties.

When excavation for a retaining wall or foundation will undermine the adjacent property - that is, remove soil support from below the neighbor's existing foundations or structures - the code requirements escalate significantly. California Civil Code Section 832 lays out four specific conditions for excavation adjacent to a property line. The excavating party must give reasonable notice stating how deep the excavation will be and when it will begin. If the excavation will be deeper than the neighbor's walls or foundations and close enough to endanger them, the neighbor must be allowed at least 30 days to take protective measures or extend their foundations. The statute defines "standard depth of foundations" as 9 feet below adjacent curb level. If excavation goes deeper than this standard depth and the neighbor has a building or structure with foundations at standard depth or deeper, the excavating owner must protect the adjacent property and structures at their own cost and is liable for any resulting damage, except for minor settlement cracks. This is an area where preconstruction coordination is not optional - it is a statutory obligation.

On the city side, LADBS and the Bureau of Engineering (BOE) require review when proposed excavation or shoring will remove lateral support from the public right-of-way. If tiebacks are proposed within the public right-of-way, BOE requires a separate E-Permit with structural review, tieback encroachment fees, and approval before LADBS will issue the building permit. The practical implication is that undermining conditions trigger a layer of coordination between the project, the neighbor, LADBS, BOE, and the respective engineers that must be identified and planned for during preconstruction, not discovered during construction.

Tieback Easements

When a soldier pile and tieback wall system is proposed along or near a lot line, the tiebacks typically extend under the adjacent property. This is a physical encroachment that requires a recorded easement from the neighboring property owner. The easement grants the right to install the tiebacks in a defined zone beneath the neighbor's property and typically includes provisions for access during installation, indemnification, insurance requirements, and obligations regarding future construction that might affect the tiebacks.

We have managed projects where the tieback easement negotiation was the critical path item that determined whether the project could proceed on schedule. On one Bel Air project, the tieback easement negotiation with the adjacent property owner took five months and required three rounds of revised structural drawings before the neighbor's engineer was satisfied. On another, the neighbor refused the easement entirely, requiring a complete redesign of the retaining wall system from tied-back soldier piles to a deeper cantilevered system at a cost increase of approximately $280,000.

Engineering and Design

Retaining walls on hillside residential properties in Los Angeles are designed by licensed structural engineers or licensed civil engineers. Not by the architect, not by the contractor, and not by the owner. This is both a legal requirement and a practical necessity. The forces involved in retaining significant heights of soil on seismically active hillside sites require professional engineering analysis, and LADBS requires stamped and signed engineered drawings for any retaining wall requiring a permit.

The licensing structure in California is worth understanding because it directly affects who designs what on a hillside project. In California, the Structural Engineer (SE) license is a "title authority" that sits on top of the Civil Engineer (CE) license - you must hold an active CE license before you can obtain an SE. Per the California Board for Professional Engineers, civil engineers may design any building or structure except hospitals and public schools, and may also perform structural and geotechnical engineering "if fully competent to do so." In practice, this means some civil engineers hold both CE and SE licenses and handle the full scope of site structural design, from grading and drainage through retaining wall structural engineering. Others focus on civil site work - grading plans, drainage design, surface water management, wall locations and alignments - and delegate all structural engineering of site walls and foundations to a dedicated structural engineer who specializes in those calculations. Neither approach is inherently better; what matters is that the person designing the wall has the specific experience and competence for the lateral loads, seismic conditions, and soil interactions that hillside retaining walls present. The geotechnical engineer, a separate discipline, evaluates soil conditions, bearing capacity, lateral earth pressures, and global slope stability. On a residential hillside project with retaining walls, all three disciplines are typically involved, and the coordination between them is critical.

How Forces Work on a Retaining Wall

Understanding the forces on a retaining wall, even at a general level, helps explain why wall costs escalate so dramatically with height and why engineering judgment matters so much. The primary force a retaining wall resists is lateral earth pressure - the horizontal force exerted by the retained soil pushing against the wall. This pressure follows a triangular distribution: zero at the top of the wall and increasing linearly with depth. At the base of a 10-foot wall retaining typical LA hillside soil with a unit weight of 120 pounds per cubic foot, the vertical earth pressure is 1,200 pounds per square foot. The lateral (horizontal) component is a fraction of that, determined by a pressure coefficient that depends on how the wall can move.

There are three states of lateral earth pressure, and which one applies depends on the wall's structural behavior. Active pressure develops when the wall is free to deflect slightly away from the soil, which is the case with a cantilevered retaining wall. The soil shears along a failure plane behind the wall and the horizontal pressure drops to its minimum value. The active pressure coefficient (Ka) is typically in the range of 0.3 to 0.4 for granular soils, depending on the soil's angle of internal friction. At-rest pressure develops when the wall is restrained from moving at all, as with a basement wall braced by floor slabs at top and bottom. The at-rest coefficient (K0) is higher, typically around 0.5, because the soil cannot mobilize its shear strength. Passive pressure develops on the toe side of the footing when the wall pushes into the soil, and is the largest of the three - the passive coefficient (Kp) can be three or more times the active coefficient. Passive resistance at the toe helps resist sliding. The geotechnical engineer specifies which pressure state applies and provides the soil parameters; the structural engineer uses those values to calculate the forces and design the wall.

Engineers express these forces in kips (one kip equals 1,000 pounds) and calculate the moments (rotational forces measured in kip-feet) that the lateral pressures create around the base of the wall. For lateral earth pressure, the total resultant force is the area of the triangular pressure diagram - one-half times the pressure at the base times the wall height - and that resultant acts at one-third of the wall height measured from the base. This is the lever arm that creates the overturning moment. For a surcharge load above the wall, the additional lateral pressure is rectangular (uniform with depth), which adds a force that acts at mid-height. For seismic loading, the added pressure distribution is inverted triangular (increasing toward the top), which raises the point of application and significantly increases the overturning moment. The structural engineer stacks all of these pressure diagrams - earth pressure, surcharge, seismic, and hydrostatic (if applicable) - to determine the total lateral force and total overturning moment the wall must resist.

A retaining wall must resist four failure modes: overturning (the wall tipping forward around its toe), sliding (the wall being pushed horizontally along its base), bearing failure (the soil under the footing being overloaded), and structural failure (the concrete or reinforcement within the wall itself being overstressed). The structural engineer calculates a factor of safety for each mode, typically requiring a minimum of 1.5 for overturning and sliding under static loads (reduced to 1.1 when seismic loads are included), and 3.0 for bearing capacity. Seismic loading can increase total lateral force by 30 to 50 percent. This is why every additional foot of wall height does not just add proportional cost - it increases the moment arm and the total lateral force, requiring thicker stems, wider footings, and heavier reinforcement to maintain adequate factors of safety.

How Water Changes Everything

Water behind a retaining wall creates hydrostatic pressure, and this is the single most important force that owners and builders underestimate. Water has a unit weight of 62.4 pounds per cubic foot. When the soil behind a wall becomes saturated because the drainage system has failed, clogged, or was never installed, the hydrostatic pressure acts as its own separate triangular distribution below the water table, independent of the earth pressure. At the base of a 10-foot wall with the water table at the top of the wall, the hydrostatic pressure alone is 624 pounds per square foot, producing a resultant force of 3,120 pounds per linear foot of wall. That force is additive to the earth pressure.

The engineering mechanics work like this: when water is present in the soil, the engineer uses the buoyant (submerged) unit weight of the soil - roughly 55 to 65 pounds per cubic foot instead of the dry weight of 110 to 120 - to calculate the lateral earth pressure component. But then the full hydrostatic water pressure is added on top of that. The net effect is that total lateral force on the wall can increase by 40 to 60 percent or more compared to the drained condition. Most retaining walls are designed for drained conditions, meaning the engineer assumes the drainage system behind the wall is functioning and the water table stays below the base of the wall. When that assumption fails, the wall is being asked to carry forces it was never designed for. This is why a clogged French drain is not a maintenance inconvenience - it is a structural loading condition that can push a wall past its design capacity.

Geotechnical Investigation

The engineering design of a retaining wall starts with the geotechnical investigation. The geotechnical engineer evaluates the soil conditions at the wall location through borings, laboratory testing, and analysis to determine the soil type, bearing capacity, shear strength, groundwater conditions, and seismic parameters. This information feeds directly into the structural engineer's design.

On hillside sites in LA, the geotechnical conditions can vary dramatically across a single property. The upper portion of a lot may be fill material from decades ago. The lower portion may be native sandstone. A clay layer in between may create a sliding plane that affects global slope stability. On sites in or adjacent to recent burn areas, debris flow hazards add another layer of geotechnical complexity - our foundation systems page covers debris flow mitigation systems, including engineered ring net barriers and deflection walls. Without a site-specific geotechnical investigation, the structural engineer is designing in the dark. For a detailed breakdown of the geotechnical investigation process - what is tested, what the report contains, and how it translates into construction decisions - see our foundation systems and geotechnical page.

How Height Drives Complexity

There are code thresholds where retaining wall requirements change significantly with height:

• Under 4 feet (no surcharge): No building permit required. This is the exemption that allows short landscape retaining walls to be built without engineering or permits.
• Over 4 feet: Building permit required. Wall must be designed by a licensed engineer. Design must address lateral earth pressure, bearing capacity, overturning, and sliding stability.
• Over 6 feet of backfill: California Building Code (CBC Section 1803.5.12) requires dynamic seismic lateral earth pressures for structures in Seismic Design Categories D, E, or F. All of Los Angeles falls into these categories. The seismic design significantly increases required wall thickness, reinforcement, and footing size.
• Over 12 feet of backfill: Design requirements escalate again: the wall must be designed per a site-specific geotechnical investigation, and seismic lateral forces must be calculated based on actual site soil conditions rather than presumptive values.

Surcharge Loading

What is above or behind the wall matters enormously. A retaining wall holding back an unloaded slope is a fundamentally different engineering problem than a wall holding back a slope with a house, pool, driveway, or other structure on it. The additional vertical load from the structure on the retained soil increases the lateral pressure on the wall. This is called surcharge loading, and it must be included in the wall design.

On hillside residential sites, surcharge is nearly always present. The retained slope almost always supports something: the neighbor's house, a driveway, a pool deck, future construction. Failing to account for surcharge, or underestimating it, is a common design error that leads to walls that are undersized for their actual loading conditions.

Global Stability

A retaining wall can be perfectly designed for its local loading conditions and still fail if the broader slope system is unstable. Global stability analysis evaluates the entire slope - including the soil mass above the wall, the wall itself, the soil mass below the wall, and the foundation conditions - to verify that the slope as a whole has an adequate factor of safety against deep-seated failure.

On hillside sites with multiple retaining walls at different elevations, global stability analysis is critical. The upper wall affects the loading on the lower wall. A failure in the upper slope can overwhelm the lower wall regardless of how well it was designed for its own loading conditions. The geotechnical engineer is responsible for the global stability analysis, and the structural engineer designs the individual wall components to work within that framework.

The Relationship to the House

Retaining walls on hillside residential sites are not independent structures. They are part of an integrated system that includes the house foundation, the drainage systems, the grading, and the overall slope geometry. The wall's performance affects the foundation. The foundation's loading affects the wall. The drainage behind the wall connects to the site drainage system that protects the foundation. Changes to one element affect the others.

This interdependence is why retaining wall design should happen in coordination with the overall structural design and geotechnical evaluation of the site, not as an afterthought. On projects where the retaining walls are designed separately from the house by a different engineer, or where the wall design is finalized before the geotechnical investigation is complete, coordination gaps are inevitable.

Permitting, Code Requirements, and Ordinance 176,445

When Permits Are Required

In the City of Los Angeles, a building permit is required for any retaining wall over 4 feet in height measured from the bottom of the footing to the top of the wall, or for any retaining wall that supports a surcharge regardless of height. This 4-foot threshold comes from the permit exemptions in the building code (LAMC Section 91.106.3.2). Below 4 feet and without surcharge, no permit is required. Above that, everything requires permits, engineered drawings, plan check, and inspections.

In Beverly Hills, the same 4-foot permit threshold applies (BHMC Section 9-1-107). However, Beverly Hills has separate development standards for the Central Area, Hillside Area, and Trousdale Estates that affect wall height, setback, and design review requirements. Building in Beverly Hills involves navigating the Beverly Hills Community Development Department rather than LADBS, with different plan check processes and timelines.

Malibu operates under the jurisdiction of the City of Malibu Community Development Department and the California Coastal Commission for properties in the Coastal Zone, which includes most of the city. Retaining walls in the Coastal Zone trigger additional permitting requirements related to view preservation, landform alteration, and environmental review.

Ordinance 176,445: The Hillside Retaining Wall Rules

This is the ordinance that most directly affects retaining wall construction on hillside residential properties in LA, and its specifics are worth understanding in detail.

The City Council passed Ordinance No. 176,445 to control the proliferation of massive retaining walls on residential lots within the Hillside Area delineated on the Bureau of Engineering Basic Grid Map No. A-13372. The ordinance was signed January 28, 2005, and its provisions apply to all permit applications submitted on or after March 9, 2005 (LADBS Information Bulletin P/ZC 2002-016). It applies to freestanding retaining walls in A or R zones (including the RA Zone) located in designated Hillside Areas.

The ordinance defines a retaining wall as "a freestanding continuous structure, as viewed from the top, intended to support earth, which is not attached to a building." According to the City Attorney's Office, the phrase "not attached to a building" exempts retaining walls that are structurally integrated as part of the building foundation, such as a basement wall. However, any portion of a retaining wall that extends beyond the building footprint is subject to the ordinance.

What the Ordinance Allows By Right

Option A: One freestanding retaining wall per lot with a maximum height of 12 feet.

Option B: In lieu of the single 12-foot wall, two retaining walls per lot with a maximum height of 10 feet each, stacked for up to 20 feet of total vertical height, separated by a minimum horizontal offset of 3 feet.

Walls that can be built without permits (under 4 feet, no surcharge) are explicitly exempt from the ordinance and do not count against the allowed number. Guardrails required by code may be placed on top of the retaining wall and are exempt from the height limitation, provided they are open guardrails per LAMC Section 91.509.3. Retaining walls 8 feet or higher must be covered with landscaping material, with the landscaping plan approved by the Department of City Planning.

Exceeding the Limits

Walls exceeding the number or height limits require approval from the Zoning Administrator under LAMC Section 12.24 X.26 (recently referenced in the new Chapter 1A as Section 4C.9.2.F, per the January 2025 City Planning filing CP13-2412.A). This is a Class 1 Conditional Use Permit process that requires neighborhood notification, posting of the site, a hearing, and a determination. It adds 6 to 12 months or more to the timeline, and approval is not guaranteed.

Walls Grandfathered Before March 2005

Existing walls that were legally built with permits before the ordinance's March 9, 2005 effective date are legally nonconforming under LAMC Section 12.23. They can be maintained and repaired. This is the "grandfathering" provision that allows pre-2005 walls exceeding current limits to remain in service.

The LADBS Unsafe Order Exception

Northeast LA Has Different Rules

While Northeast LA is outside the core Westside hillside market, it is worth noting that properties within the Northeast Los Angeles Community Plan Area are subject to Ordinance 180,403, which imposes stricter retaining wall standards: the maximum total height of all freestanding retaining walls cannot exceed 12 feet, no individual wall can exceed 6 feet, each wall is limited to 75 feet in linear length, and walls must be separated by a horizontal distance equal to the height of the tallest wall. The point is that retaining wall regulations vary by area, and the specific overlay zone for any given property must be confirmed before design begins.

Grading Permits vs. Building Permits

Retaining walls in the City of Los Angeles often require both a building permit (for the wall structure itself) and a grading permit (for the excavation, backfill, and fill associated with the wall construction). In Hillside Areas, grading permits are required for virtually all excavation work, and the grading permit must be issued concurrently with the retaining wall building permit.

Plan Check and Common Corrections

LADBS plan check for retaining walls reviews the structural calculations, the drainage design, the site plan showing the wall location relative to property lines and structures, and compliance with the hillside ordinance limitations on wall height and number. Common plan check corrections include insufficient drainage detail behind the wall, missing seismic design for walls retaining more than 6 feet, inadequate surcharge analysis, missing global stability analysis for walls on steep slopes, and non-compliance with Ordinance 176,445 regarding height limits and number of walls.

Inspection Requirements

During construction, retaining walls in LA are subject to inspections at multiple stages: footing inspection, stem rebar inspection, drainage inspection before backfill, and backfill compaction inspection. For walls requiring special inspection (which includes most structural retaining walls in Seismic Design Categories D through F), a deputy inspector must be on site during critical construction activities including rebar placement and concrete pour.

In Hillside Areas, retaining walls and associated shoring that are not within the footprint of the building are inspected by the LADBS Grading Division, not the Residential or Commercial Division. This is a procedural detail, but it matters because the Grading Division has its own inspection scheduling process and inspectors with specific expertise in earthwork and retaining structures.

Permit Timeline Reality

For a straightforward retaining wall with no zoning variances and no Hillside Ordinance complications, plan check typically takes 4 to 8 weeks for the initial review and 2 to 4 weeks for each subsequent correction cycle. Most retaining wall submittals go through at least one correction cycle. For walls that trigger Zoning Administrator review under Ordinance 176,445, add 3 to 6 months or more for the ZA process. In Beverly Hills and Malibu, the timelines are different but not necessarily faster. For detailed permitting information, see Los Angeles Permitting Overview, and for how retaining wall permitting fits within the overall project schedule, see our construction timeline guide.

Construction Process

Building a structural retaining wall on a hillside lot in Los Angeles is a sequence of operations that must be executed in the right order, with the right equipment, and with continuous coordination between the field crew, the structural engineer, the geotechnical engineer, and the inspector.

Excavation, Layback Slopes, Temporary Support, and Slot Cuts

Before you can build a permanent wall, you have to excavate to the footing elevation. On a hillside site, that excavation removes the soil that is currently providing support to the slope above, and the slope responds to the removal of support immediately. This is why excavation strategy is one of the most important decisions on any hillside retaining wall project.

The preferred approach, when site geometry allows, is to lay back the slope before building the wall. OSHA's excavation standards (29 CFR 1926 Subpart P) and Cal-OSHA requirements govern how steep an unsupported cut can be. In Type B soils (common on LA hillsides), the maximum allowable slope is 1:1 (45 degrees) for excavations under 20 feet. In Type C soils (loose or granular material), the requirement increases to 1.5:1 (34 degrees). Vertical cuts are limited to approximately 5 feet in favorable soil conditions before sloping or shoring is required. On hillside residential sites, the geotechnical engineer determines the allowable cut slopes and vertical cut heights based on the specific soil conditions encountered. The ideal sequence is to lay back the slope to a stable angle, build the wall, waterproof the retained face, install the drainage system, then backfill in controlled lifts with compaction certified by the geotechnical engineer.

When the site does not allow for laying back the slope - because the lot is too narrow, because there is an adjacent structure, or because the required layback would extend beyond the property line - temporary shoring must be installed before the permanent wall excavation proceeds.

Where full temporary shoring is not warranted by the conditions but the excavation is adjacent to an existing structure or property line, slot cut excavation is a sequenced technique that allows wall construction without conventional shoring. The work face is divided into alternating sections. In the most common configuration, sections are designated A and B. All A sections are excavated first while the B sections remain as unexcavated soil buttresses that provide passive resistance and prevent the adjacent structure's foundation from losing lateral support. Once the A sections are constructed and achieve adequate strength, the B sections are excavated. Some geotechnical engineers specify a three-phase A-B-C sequence for longer walls or more sensitive adjacent conditions, where only every third section is open at any time. Slot widths are typically 6 to 8 feet, determined by the geotechnical engineer based on soil conditions and proximity to structures.

Access Challenges

Hillside construction in LA's premier neighborhoods presents access challenges that significantly affect retaining wall construction logistics and cost. Many streets in the Bird Streets, Bel Air, the Palisades Riviera, and the Malibu canyons are narrow, steep, and winding. Getting a drill rig, a concrete pump, a crane, or even a loaded concrete truck to the project site can require traffic control, temporary road modifications, and advance coordination with the city. Our hillside site development page covers the logistics planning that precedes structural work on these sites.

On sites where equipment cannot reach the wall location by road, materials and equipment must be crane-lifted or conveyed by other means. We have managed projects where every cubic yard of concrete was pumped over 200 feet from the closest point a concrete truck could park. That adds time and cost to every pour.

Rebar: Grades, Cover, Shop Drawings, and Submittals

Reinforcing steel is the structural backbone of every concrete retaining wall. The details of rebar specification, fabrication, and installation are worth understanding because errors in this phase are costly to correct and directly affect the wall's structural capacity and longevity.

Most residential retaining walls in LA use Grade 60 rebar (60,000 PSI yield strength, ASTM A615). Epoxy-coated rebar (ASTM A775) is specified in corrosive soil conditions, where the water table is high, or in coastal areas like Malibu where salt exposure accelerates corrosion of unprotected steel. Epoxy coating adds cost and lead time but significantly extends the service life of the reinforcement in aggressive environments.

Concrete cover - the distance from the outer face of the concrete to the nearest rebar - is the primary defense against corrosion. ACI 318 specifies minimum cover requirements:

• 3 inches: Concrete cast against and permanently in contact with ground (the earth side of a retaining wall)
• 2 inches: #6 through #18 bars exposed to weather
• 1.5 inches: #5 and smaller bars exposed to weather

The rebar fabrication process follows a specific sequence. The structural engineer's design drawings show rebar sizes, spacing, and details. The rebar fabricator produces rebar drawings (sometimes loosely called shop drawings) from those design drawings, showing every bar: size, length, bend dimensions, spacing, lap splice locations, and relationship to adjacent bars. The structural engineer reviews and approves the rebar drawings before fabrication begins. This review cycle typically takes 1 to 3 weeks.

Control Joints and Construction Joints

Every concrete retaining wall cracks. The question is whether the cracking is controlled or uncontrolled. Control joints and construction joints are two different mechanisms for managing this reality, and confusing them is a common source of problems.

A control joint (contraction joint) is a deliberate weakened plane in the wall that predetermines where shrinkage cracking will occur. As concrete cures, it shrinks, and the resulting tensile stress must be relieved somewhere. Without control joints, the wall cracks randomly. Control joints are typically placed every 20 to 30 feet, formed by inserting a strip of material or by saw cutting after initial set. The joint depth is typically one-quarter to one-third of the wall thickness. Whether reinforcing steel is continuous or discontinuous across control joints depends on the structural engineer's design; the engineer balances the need for the joint to relieve stress against the structural continuity requirements of the wall.

A construction joint (cold joint) is a planned stopping point where one concrete pour ends and the next begins. On a long retaining wall, it is not always possible or practical to pour the entire wall in one operation. The surface of the previous pour is roughened, cleaned, and treated with a bonding agent before the next pour. Reinforcing steel is continuous across construction joints, with dowel bars extending from the completed pour into the next section. The intent is to create a structurally sound connection that transfers forces across the joint, though a cold joint is never truly monolithic since the concrete on each side cured at different times.

The critical distinction: control joints allow movement. Construction joints should not. A control joint is designed to crack in a controlled manner and accommodate shrinkage and thermal movement. A construction joint is designed to transfer all forces across the joint as if the wall were continuous.

On tall walls poured in two stages (footing first, then stem), the interface between footing and stem is a construction joint. Vertical rebar extending from the footing into the stem - called dowels - provides continuity. Getting the dowel location, spacing, and projection height correct during the footing pour is essential because adjusting misplaced dowels after the footing has cured is expensive and structurally compromising. When one retaining wall meets another at a different elevation or changes direction, the vertical doweling between the walls must be detailed on the structural drawings and executed precisely. Where the wall retains habitable space or where hydrostatic pressure is a concern, a PVC or rubber waterstop is embedded in the construction joint between the footing and stem wall. The waterstop spans the joint and creates a continuous barrier against water migration through the cold joint. Waterstops are standard practice on basement walls and below-grade walls retaining water, and are specified by the structural engineer based on the wall's exposure conditions.

Architecturally Exposed Concrete and Board-Formed Walls

On high-end residential projects in Bel Air, the Palisades, and Beverly Hills, retaining walls are frequently specified as architecturally exposed concrete. Board-formed walls, smooth-formed walls, and textured concrete require a fundamentally different level of construction precision than standard retaining walls, and the cost reflects that.

Board-formed concrete uses real lumber as formwork - typically rough-sawn Douglas fir, cedar, or redwood - to imprint the wood grain pattern into the concrete surface. The formwork preparation is where the craft lives. The interior face of the lumber (the face against the concrete) is sandblasted to raise the grain and create a more pronounced texture transfer. Different wood species and different sandblasting pressures produce distinctly different grain patterns: Douglas fir gives a strong, defined grain; cedar produces a finer, tighter pattern; redwood falls somewhere in between. The amount of sandblasting directly controls the depth of the grain impression.

This is a mock-up process: the concrete contractor builds sample panels using different wood species and sandblasting levels, the architect and owner select the preferred finish, and the selected treatment is then applied consistently across all formwork. The lumber must be sealed on the non-concrete face to prevent moisture absorption that causes differential curing and discoloration. Form ties must be snap-ties or she-bolts with removable cones, positioned in a deliberate, regular pattern because the tie holes become a visible element of the finished wall.

The concrete mix for architectural walls requires higher cement content, controlled aggregate size, and specific admixture packages. The pour must be continuous - stopping mid-wall creates a visible cold joint that cannot be concealed. Pour rate must balance continuous placement against hydrostatic pressure on the forms. Vibration must be thorough but controlled: under-vibration leaves bug holes, while over-vibration causes aggregate segregation visible as discoloration bands.

Waterproofing, Efflorescence Prevention, and the Shoring-to-Wall Interface

The waterproofing system on a retaining wall serves two functions: keeping water out of habitable space behind the wall, and protecting the concrete and reinforcing steel from moisture-related deterioration over the wall's service life.

For standard retaining walls not adjacent to habitable space, a damp-proof coating on the earth-side face provides adequate protection. The real protection comes from the drainage system: perforated subdrain pipe at the base, gravel drainage blanket up the back face, filter fabric, and weep holes. If the drainage works, the waterproofing barely has to.

For walls retaining habitable space (basement walls, below-grade rooms), full waterproofing is required. The industry standard in LA subterranean construction is a sheet membrane applied to the earth-side face, protected by a drainage mat, with a subdrain at the base.

When a permanent retaining wall is built inside temporary soldier pile shoring, the waterproofing challenge changes. The shoring is already in place against the earth, and there is no access to the earth-side face of the permanent wall after it is poured. This is where blindside (pre-applied) waterproofing becomes necessary. The membrane is applied to the face of the shoring lagging before the permanent wall is poured, and the concrete is placed directly against the membrane. The gap between the shoring and the permanent wall is also where the subdrain system is installed.

Efflorescence - the white crystalline deposit on concrete surfaces - is caused by water migrating through the wall, dissolving calcium hydroxide and other soluble salts, and depositing them on the exposed face as the water evaporates. It is not structural damage, but it signals ongoing moisture migration that will eventually corrode the reinforcing steel. The prevention hierarchy is: proper drainage behind the wall, quality waterproofing on the earth-side, low water-to-cement ratio in the concrete mix, penetrating sealers on the exposed face, and integral waterproofing admixtures (crystalline products such as Xypex or Kryton) added to the concrete mix.

Drainage Installation

The drainage system behind a retaining wall is installed during construction, before the wall is backfilled. The typical system includes a perforated subdrain pipe (usually 4-inch perforated PVC or HDPE) at the base of the wall, wrapped in filter fabric and bedded in gravel. A gravel drainage blanket extends up the back of the wall, typically 12 to 18 inches thick, with filter fabric separating the gravel from the native or engineered backfill soil. Weep holes through the wall face (typically 4-inch PVC pipes at 6- to 10-foot spacing) provide outlets for water that reaches the wall.

The subdrain connects to the site's overall drainage system and must discharge to an approved point. On hillside sites, the subdrain routing can be complex because gravity drainage requires continuous downhill fall to the discharge point. Getting the drainage right is not optional. It is the single most important factor in the long-term performance of the wall.

French drain failure is one of the most common long-term maintenance problems with retaining walls, and on hillside properties the consequences of drain failure are amplified because the hydrostatic pressure builds against walls retaining significant soil heights. The primary failure mechanism is silt migration: fine soil particles (silt and clay) gradually work through the filter fabric surrounding the gravel drainage blanket, filling the void spaces between the gravel and reducing or eliminating the drainage capacity. This happens even with proper fabric if the wrong weight or type is specified for the soil conditions. Professional-grade non-woven geotextile (4 to 6 ounce weight, needle-punched polypropylene) is the correct specification for retaining wall drainage. Cheap landscape fabric or woven geotextile used as a substitute will degrade in wet soil within a few years, allowing unrestricted soil migration into the drain rock. Tree roots infiltrate perforated drain pipes through the perforations, forming dense masses that obstruct water flow entirely. In areas with hard water, calcium and mineral deposits can cement the gravel over time, reducing permeability. The result in each case is the same: the drainage system stops draining, hydrostatic pressure builds behind the wall, and the wall begins to fail. Prevention includes specifying the correct geotextile for the soil type, wrapping the entire gravel-and-pipe assembly in fabric (the "burrito wrap" method), ensuring the gravel drainage blanket extends the full height of the wall face, installing cleanouts at accessible points so the subdrain can be flushed or snaked, and routing the discharge to a visible daylight point where flow can be confirmed after a rain event. On walls where long-term drainage performance is critical, adding a drainage mat (dimple board) between the waterproofing and the backfill provides an additional drainage path that is less susceptible to clogging than the gravel blanket alone.

Backfill, Compaction, and Deflection Monitoring

Backfill behind the wall must be placed in controlled lifts and compacted to the specification in the geotechnical report, typically 90 to 95 percent relative compaction. On hillside sites, the backfill material itself may need to be imported engineered fill rather than native soil. Each lift of backfill is tested for compaction by a soils testing firm, and the results are compared to the specification.

Deflection monitoring during backfill is a critical quality control measure on taller walls and walls adjacent to sensitive structures. As each lift of backfill is placed and compacted, the lateral pressure on the wall increases incrementally. The wall deflects (moves outward) in response. On most walls, this deflection is within the design tolerance and is expected. But on walls where the margin is tight, where adjacent structures are close, or where the wall system is cantilevered without tiebacks, monitoring the deflection during backfill provides real-time confirmation that the wall is performing as designed.

Deflection monitoring is typically done with survey points established on the wall face before backfill begins. A surveyor measures the position of each point before each lift of backfill and again after compaction. If the measured deflection exceeds the structural engineer's specified tolerance, backfill operations stop and the engineer evaluates whether the wall needs additional support before proceeding. On walls where rakers or struts are providing temporary lateral support, the rakers are removed incrementally as the permanent backfill provides the design lateral resistance, and deflection is monitored at each stage of raker removal.

Construction Sequence

Quality Control, Special Inspection, and Timeline

Structural retaining walls in Seismic Design Categories D through F (all of Los Angeles) require special inspection for concrete placement and reinforcement. A deputy inspector, engaged by the owner (not the contractor), must observe and verify rebar placement, concrete placement, and curing. Concrete test cylinders are taken during each pour and tested at 7 and 28 days to verify the concrete meets the specified compressive strength.

For a typical cast-in-place cantilever wall of moderate height (6 to 10 feet) and length (50 to 100 linear feet) on a site with reasonable access, construction typically takes 6 to 10 weeks from start of excavation through backfill completion. Soldier pile and tieback walls over longer runs and greater complexity typically take 10 to 16 weeks. These timelines assume permits are in hand and the design is final.

Retaining Wall Repair vs. Replacement

When a retaining wall shows signs of distress, the first question is whether the wall can be repaired in place or whether it needs to be fully replaced. The answer depends on the cause of the distress, the wall's original construction quality, and the cost comparison between repair and replacement.

When Repair Is Feasible

Repair is feasible when the wall's structural system is fundamentally sound but has localized damage or a correctable deficiency. Common repair scenarios include walls with drainage failures where the wall structure is intact but water has caused localized distress, and underpinning the footing with micropiles or push piers where bearing soil has deteriorated. Crack injection using epoxy or polyurethane grout can restore some structural continuity, though on walls with systemic structural deficiency it is a temporary measure that addresses the symptom without correcting the underlying cause. Carbon fiber reinforcement strips bonded to the wall face are sometimes proposed to add tensile capacity, but on hillside walls with fundamental design deficiencies, underpinning and structural reinforcement are generally more reliable long-term solutions.

When Replacement Is Necessary

Replacement is necessary when the wall's fundamental structural capacity is insufficient for the loading it carries, when the wall was built without reinforcement or without engineering, when the wall has deteriorated to the point where repairs would cost more than replacement, or when the wall's geometry or location no longer suits the property's current or planned use.

The false economy of patching a wall that needs to be rebuilt is something we see frequently. An owner spends $40,000 to $80,000 on crack repair, drainage improvements, and cosmetic work on a wall that was never engineered, has no reinforcement, and is slowly rotating under load. Three years later, the wall fails and the replacement costs $250,000 or more. The repair money was wasted because it addressed symptoms without correcting the underlying problem.

Building a New Wall in Front of a Failed Wall

This question comes up frequently: can you build a new retaining wall on the downhill side of a failing wall to provide the retention the old wall can no longer deliver? The answer is technically possible but practically problematic in most LA hillside situations.

• You lose the horizontal distance equal to the new wall's thickness plus any construction gap - which on tight hillside lots may not be available
• The failed wall becomes trapped fill behind the new wall, adding unpredictable surcharge loading
• The new wall's footing excavation may undermine what remains of the old wall's stability
• Under Ordinance 176,445, you may now have two walls on the lot, triggering the two-wall height limit

The more common approach for a truly failed wall in LA is to demolish and replace in sections using slot cuts or temporary shoring, or to install soil nails and shotcrete over the existing failed face as a stabilization measure that reinforces the existing wall in place.

The Nonconforming Replacement Dilemma

The Discovery Problem

One of the most challenging aspects of retaining wall repair is that you do not always know what you are dealing with until you start investigating. A wall that looks like a simple crack repair from the surface can reveal complete absence of reinforcing steel, no drainage system, an undersized footing, or deteriorated concrete once you open it up. A construction manager manages this discovery process by establishing a scope that accounts for likely discovery conditions, communicating findings to the structural engineer in real time, and developing recommendations based on what is actually found rather than what was assumed.

Emergency Stabilization

When a retaining wall fails during a rain event or shows signs of imminent collapse, emergency stabilization takes priority over permanent repair. Emergency measures may include temporary shoring to prevent further movement, dewatering or emergency drainage to relieve hydrostatic pressure, soil removal to reduce surcharge loading, and barriers to protect downhill properties or roadways. The cost of emergency stabilization typically ranges from $25,000 to $150,000 depending on severity and scale, and this cost is in addition to the permanent repair or replacement.

LADBS has authority to issue emergency permits for work necessary to stabilize unsafe retaining walls. The scenario is a wall that is visibly failing or clearly about to fail - significant movement, active cracking during a rain event, soil sliding behind or around the wall, or an imminent collapse that threatens a structure, roadway, or occupied property below. In these situations, waiting weeks or months for standard plan check is not an option. The owner or contractor contacts LADBS to report the hazard. An inspector is dispatched to evaluate the condition and classify the severity. If the conditions present an immediate hazard to life or property, LADBS can issue an emergency permit that authorizes stabilization work to begin immediately, bypassing the normal plan check timeline. The emergency permit allows the contractor to mobilize, shore the failure area, dewater if needed, remove unstable soil, and perform whatever temporary or permanent stabilization the structural engineer specifies to arrest the failure and make the site safe.

The critical constraint is that the emergency permit covers only the emergency stabilization scope - shoring, temporary drainage, soil removal, or whatever is needed to eliminate the immediate hazard. It does not cover permanent reconstruction, redesign, or any unrelated work on the property. All conditions of the emergency permit must be cleared and closed before LADBS will process any additional permits on the project. If the emergency stabilization is part of a larger renovation, addition, or new construction, the permanent work requires its own separate permit through the standard plan check process. This means the emergency permit cannot be used to bootstrap broader construction activities. It exists to address the hazard, and that is all it authorizes.

Separately, LADBS has a code enforcement process for identifying and compelling repair of defective or failing retaining structures. This typically begins with a Notice of Code Violation, followed by a Notice and Order to Comply if the owner does not respond. If conditions constitute a serious hazard, LADBS can issue a Substandard Order declaring the structure unsafe, which may require immediate corrective action, restrict occupancy, or in extreme cases order demolition. For retaining walls that were built without permits or that have deteriorated to the point of being unsafe, initiating engagement with LADBS proactively, before a complaint triggers enforcement, gives the owner more control over the timeline and approach to remediation.

Grading Bonds

On hillside projects involving significant earthwork, LADBS requires a grading bond before issuing the grading permit. Under LAMC Section 7006.5, a surety or cash bond is required for any excavation or fill exceeding 250 cubic yards of earth in a designated hillside grading area. The bond amount is calculated on a sliding scale based on total earthwork volume: $1,000 plus $1.00 per cubic yard for the first 10,000 cubic yards, with reduced per-yard rates for larger volumes. The bond calculation must also include the cost of all drainage and protective devices, including retaining walls, that are required as part of the grading plan. The bond exists so that if the work is not completed in accordance with the approved plans, the city has funds to correct hazardous conditions. On a residential hillside project where retaining walls are part of a larger grading scope, the grading bond can add a meaningful cost that needs to be factored into the preconstruction budget. The bond is released in installments as the grading work is completed and approved by LADBS inspection.

Cost

Retaining wall costs in the Los Angeles luxury residential market bear little resemblance to the national averages published by home improvement websites. Those sources quote $3,000 to $10,000 for a retaining wall, which might be accurate for a 3-foot landscape block wall in a flat Midwestern backyard. On hillside properties in Pacific Palisades, Bel Air, Malibu, and Beverly Hills, structural retaining walls routinely cost $100,000 to $500,000, and total retaining wall expenditure on a complex hillside project can exceed $800,000. Our LA construction cost guide provides a comprehensive breakdown of how retaining wall costs fit within the full budget structure of luxury residential projects in this market.

What Drives Cost

The primary cost drivers for retaining walls on LA hillside properties are wall height, wall length, soil conditions, access constraints, wall type, drainage requirements, permit complexity, and shared-wall coordination. Of these, height has the most dramatic impact because every additional foot of height increases the lateral force on the wall, which increases the required footing width, wall thickness, and reinforcement. The cost per square foot of wall face increases with height, not proportionally but exponentially.

Cost Ranges by Wall Type and Height

The following ranges are for structural retaining walls on hillside residential properties in the LA luxury market, including engineering, permits, construction, drainage, and backfill.

Cast-in-Place Reinforced Concrete Cantilever Walls

Soldier Pile and Lagging (with Tiebacks)

Shotcrete Walls

These ranges are wide because the variables are significant. A 10-foot cantilever wall on a lot with good access, stable soil, and no shared-wall complications costs far less than a 10-foot wall on a narrow hillside street with poor access, expansive clay soil, a high water table, and a tieback easement that took four months to negotiate. Both walls are 10 feet tall. The scope is completely different.

The Cost of Not Knowing Early

Retaining wall surprises during construction are one of the most common sources of budget overruns on hillside projects. The owner and architect design a house based on a conceptual grading plan that shows the lot as essentially flat. During preconstruction, the geotechnical investigation reveals that the "flat" pad requires retaining walls along the uphill property line and side yards that were not in the original budget, supported on deep foundations with piles and grade beams. What looked like a simple grading exercise becomes $200,000 to $400,000 in retaining wall scope that was never priced. This is the same dynamic described on our foundation systems page - site conditions, not the structure above, drive the cost divergence between flat lot and hillside projects. Preconstruction investigation that identifies retaining wall requirements before design is finalized prevents six-figure surprises. Our feasibility study process is designed to surface exactly these conditions early.

Why Bids Vary So Dramatically

Two bids for the "same" retaining wall can differ by 50 to 100 percent because the scope assumptions are different. One contractor includes the drainage system, the other does not. One includes temporary shoring, the other assumes the excavation will stand unsupported. One includes the structural engineering, the other assumes the owner will provide it separately. One includes compaction testing, the other does not. One includes the tieback easement coordination, the other has never heard of it. Understanding what is and is not included in a retaining wall bid is critical to making an informed decision, and our construction cost guide explains the budget categories and scope boundaries that separate meaningful bids from incomplete ones.

The Construction Manager's Role

On projects with significant retaining wall scope, the construction manager's involvement spans from preconstruction through construction completion and is focused on the coordination, cost management, and risk mitigation that retaining wall work demands.

During preconstruction, the CM reviews the geotechnical report and structural drawings for constructability, evaluates equipment access and shoring strategy, initiates neighbor coordination and tieback easement discussions where required, develops the retaining-wall-specific budget with detailed cost categories for engineering, permits, shoring, wall construction, drainage, backfill, testing, and inspection, and identifies the sequencing constraints that retaining wall construction creates for the overall project schedule. Our budget and cost control process describes how these line items are developed and tracked. The CM engages the specialty shoring engineer early, coordinates the rebar shop drawing review cycle to prevent schedule delays, and ensures the waterproofing approach is resolved before concrete work begins.

During construction, the CM coordinates between the structural engineer, geotechnical engineer, and field conditions. Hillside retaining wall construction regularly encounters conditions that differ from the design assumptions: unexpected soil conditions at the footing elevation, groundwater not predicted by the geotechnical report, rock that prevents pile drilling to the designed depth. Each of these requires real-time communication between the field, the engineer, and the owner to evaluate the condition, develop a response, and adjust the scope and budget accordingly.

This page provides general information about retaining walls in Los Angeles residential construction and is not intended as structural, geotechnical, or legal advice. Specific projects require evaluation by licensed professionals. Regulatory information reflects conditions as of February 2026; ordinances and requirements are subject to change. Consult LADBS, LA City Planning, and applicable agencies for current requirements applicable to your property.