Due Diligence Before Buying a Lot in Los Angeles

Buying a lot or a teardown property in Los Angeles is a construction decision disguised as a real estate transaction. The listing price, the view, the neighborhood, and the square footage on the MLS sheet are the starting point, but the site conditions are what determine the project you can build, how long it will take, and what it will cost. Evaluating the regulatory constraints, geological conditions, and construction logistics before closing allows buyers to enter a project with a clear picture of the total investment and a realistic scope for what the lot can support.

This is especially true in Los Angeles, where the combination of mountainous topography, complex geology, aggressive seismic conditions, layered regulatory jurisdictions, and some of the highest construction costs in the country creates a landscape where two adjacent lots on the same street can have completely different construction realities. One lot may require $200,000 of site work before vertical construction begins. The lot next to it may require $2,000,000. That difference originates in subsurface conditions, regulatory overlays, and infrastructure factors that are evaluated through construction-specific due diligence, which supplements the standard real estate transaction analysis.

Slope density calculations, geotechnical conditions, PGRAZ designations, easement impacts on buildable area, and utility connection costs are construction evaluation questions that supplement the information available in MLS listings and preliminary title reports. This page covers those construction-specific factors.

Last updated: February 2026

What You're Actually Buying

When you purchase a buildable lot or a teardown property in Los Angeles, you are buying five things simultaneously: a specific geological condition, a regulatory envelope that determines what can be built, an access and infrastructure situation, a set of neighbor relationships that may affect construction, and a set of existing conditions - retaining walls, drainage systems, vegetation, structures, and fill - that may cost as much to address as the house itself.

The geological condition is the starting point. The lot sits on something: bedrock, sandstone, alluvial deposits, ancient landslide debris, or uncertified fill placed by a developer decades ago. That subsurface condition determines what kind of foundation the house requires, how deep it needs to go, whether retaining walls need pile support, and whether the lot is stable enough to build on at all. On a flat lot in Santa Monica or Brentwood, the geology is usually straightforward and foundation costs are predictable. On a hillside lot in Bel Air, the Palisades, or Malibu, the geology can vary dramatically from one side of the lot to the other, and foundation costs alone can range from $200,000 to over $1,000,000.

The regulatory envelope is what the City (or County, in the case of unincorporated areas) allows you to build. This includes the zoning designation, the applicable height limits, setback requirements, Floor Area Ratio, any specific plan or overlay zone restrictions, hillside ordinance requirements, and fire zone requirements. These constraints interact with each other, and the cumulative effect on a hillside lot is often more restrictive than any single regulation suggests. A 15,000-square-foot hillside lot, for example, may support 3,000 or 4,000 square feet of above-grade living area once the slope band analysis, setbacks, and height envelope are applied. Running the slope analysis early in due diligence establishes realistic expectations for the project scope the lot can support.

Access and infrastructure are worth evaluating early because they directly affect construction cost. Can a concrete truck reach the site? Is there an existing sewer connection, or does the property require a septic system? Does the water pressure support a large residence, or will it need a booster pump and storage tank? Is the electrical service capacity sufficient for a modern home with HVAC, pool equipment, and an EV charger? On flat lots with standard street access, these questions have straightforward answers. On hillside lots accessed by substandard streets, private roads, or shared driveways, answering them during due diligence provides clarity on a significant cost variable.

Existing conditions transfer with the property. Existing retaining walls, whether structurally sound or requiring repair, become part of the project scope. Existing drainage patterns, including runoff from uphill properties, need to be accommodated in the site design. Existing vegetation, particularly protected trees, may influence building footprint placement. Existing fill, particularly fill placed before the city's 1963 grading ordinance, may need to be excavated and recompacted before new construction can proceed. Assessing these conditions during due diligence allows the buyer to incorporate them into the project budget and scope.

Comparable sales data for buildable lots has a significant limitation: none of these factors appear in the transaction records. Two lots that sold for the same price on the same street can have construction cost differences of a million dollars or more because one has favorable geology and standard access while the other has landslide-prone soils, a substandard hillside street, and requires $600,000 in retaining walls before the foundation is poured. The lot purchase price is one variable in the total project equation, and it is not always the largest one.

ZIMAS and the Regulatory Envelope

The most useful free tool available for evaluating a building lot in the City of Los Angeles is ZIMAS - the Zone Information and Map Access System, maintained by the Department of City Planning at zimas.lacity.org. It is the starting point for any regulatory analysis of a lot within the City of LA.

ZIMAS is a web-based mapping application that provides parcel-specific planning and zoning information for every property in the City of Los Angeles. You can search by property address, assessor parcel number, street intersection, or case number. The system aggregates data from the Department of City Planning, LADBS, LAFD, and other city departments into a single interface that displays the regulatory constraints applicable to any given parcel.

When you pull up a property in ZIMAS, the system displays several categories of information. The Zoning Information section shows the property's zone designation (R1, RE, RA, and their subzones), which determines the basic development standards: density, height, setbacks, and Floor Area Ratio. The General Plan designation shows the city's long-term land use plan for the area. The Specific Plan section shows whether the property falls within any of the city's specific plan areas, which impose additional development standards that may override or supplement the base zoning code. The Overlay section shows whether the property is in a Historic Preservation Overlay Zone (HPOZ), a Community Design Overlay, or any other supplemental regulatory layer.

For lot evaluation, the most critical ZIMAS information falls into two categories: the development standards and the hazard designations.

The development standards tell you what you can build, in theory. The zone determines the base Floor Area Ratio, which limits total building area relative to lot size. Height districts control maximum building height. Setback requirements control how far the building must be from property lines. In Hillside Areas, the Baseline Hillside Ordinance (BHO) applies additional restrictions that modify setbacks, height, grading, and buildable area based on slope conditions.

The hazard designations tell you what challenges the site presents. ZIMAS displays whether the property is in any of the following: a Very High Fire Hazard Severity Zone (VHFHSZ), an Alquist-Priolo Earthquake Fault Zone, an Earthquake-Induced Landslide Zone, a Liquefaction Zone, a Flood Zone, a Hillside Grading Area, or a Methane Zone. Each of these designations triggers specific investigation and compliance requirements that add cost and time to the project. A property in an Alquist-Priolo Fault Zone, for example, requires a fault rupture investigation before any habitable structure can be permitted, which involves trenching across the property to locate and characterize any active faults - a process that costs $30,000 to $80,000 or more and can take months.

The specific ZIMAS flags that indicate significant construction complexity include: Hillside Area (subjects the property to the Baseline Hillside Ordinance), Hillside Grading Area (triggers additional grading investigation and restrictions), Very High Fire Hazard Severity Zone (requires fire-resistant construction assemblies and defensible space), any of the earthquake-related hazard zones (triggers geological investigation requirements), and any Specific Plan designation (imposes additional review and potentially discretionary approval requirements). A property that carries several of these designations simultaneously - which is common for hillside lots in the Palisades, Bel Air, and Malibu - faces a compounding set of regulatory requirements that extends both the permitting timeline and the project cost.

One critical limitation of ZIMAS: it only covers properties within the City of Los Angeles. Properties in unincorporated Los Angeles County (including portions of the Santa Monica Mountains, Malibu, and Altadena) are not covered. For unincorporated areas, LA County Planning's Z-NET system provides similar zoning lookup functionality. Properties within the City of Malibu have their own planning department and are subject to the city's Local Coastal Program, which adds an entirely separate layer of regulatory review. Properties in Beverly Hills, Santa Monica, and other incorporated cities within Los Angeles County each have their own zoning and planning systems. Always confirm which jurisdiction governs a property before starting your regulatory analysis.

The Slope Density Formula and Buildable Area

The slope density formula and the related Baseline Hillside Ordinance are among the most consequential regulatory constraints in LA hillside construction, and they deserve their own section because they directly determine how much house you can build on a hillside lot.

The City of Los Angeles uses two related but distinct mechanisms to regulate development density and building size on hillside properties. The slope density formula (LAMC Section 17.05) limits the number of dwelling units that can be created on a hillside subdivision parcel based on the average natural slope of the land. The Baseline Hillside Ordinance (BHO, LAMC Section 12.21 C.10) limits the maximum Residential Floor Area (RFA) of a house on any lot within the designated Hillside Area, using a slope band analysis that accounts for varying slope conditions across the property.

For individual custom home lot buyers, the BHO slope band analysis is the regulation that matters most. Here is how it works.

The slope band analysis divides the lot into bands based on the angle of the slope across different portions of the property. Each slope band is assigned a Floor Area Ratio (FAR) that decreases as the slope increases. The maximum Residential Floor Area is calculated by multiplying the area within each slope band by the corresponding FAR and summing the results.

In the R1 zone (the most common single-family residential zone in LA's hillside areas), the FAR values by slope band are approximately as follows: for slopes of 0 to 15 percent, the FAR is 0.50; for slopes of 15 to 30 percent, the FAR drops to 0.45 to 0.39 (depending on the specific zone subarea); for slopes of 30 to 45 percent, the FAR drops further to approximately 0.39 to 0.30; for slopes of 45 to 60 percent, the FAR is approximately 0.30 to 0.20; for slopes of 60 to 100 percent, the FAR drops to approximately 0.20 to 0.10; and for slopes over 100 percent (45 degrees or steeper), the FAR is zero, meaning that area of the lot generates no buildable floor area at all.

The practical impact is dramatic. Consider a 15,000-square-foot lot. If the lot is flat (0 to 15 percent slope throughout), the R1-1 zoning allows an RFA of roughly 7,500 square feet (15,000 x 0.50). If the same lot has an average slope of 50 percent, the calculation changes entirely. The FAR for steep slope bands drops so significantly that the same 15,000-square-foot lot might yield a maximum RFA of only 3,000 to 4,000 square feet. And if a substantial portion of the lot exceeds 100 percent slope, those areas contribute zero buildable area to the calculation.

The BHO provides a Guaranteed Minimum Residential Floor Area to prevent the slope band formula from making lots entirely unbuildable. In the R1 and RS zones, the minimum guaranteed RFA is 1,000 square feet (increased to 1,500 square feet in some subareas). The ordinance also allows a 20 percent RFA bonus if the project meets certain design criteria, such as proportional story sizing, front facade stepbacks, minimal grading commitments, or LEED certification. A 30 percent bonus is available for projects that qualify under the guaranteed minimum provision and exercise one of the seven design options specified in the ordinance.

The slope band analysis requires a topographic survey of the property prepared by a licensed surveyor or civil engineer, with contour intervals of no more than 10 feet. A qualified professional then measures the area within each slope band and calculates the resulting maximum RFA. For rough preliminary estimates before commissioning a full survey, the topographic contours on Navigate LA (the city's GIS mapping system) provide a general sense of the slope conditions, though the official calculation requires a stamped survey and professional analysis.

The relationship between the slope band analysis, setback requirements, height limits, and grading limits creates a compounding effect worth understanding early. The slope bands determine total floor area. The setbacks define the buildable footprint. The height limits (measured as an envelope that follows the slope of the lot) constrain the vertical massing. And the grading limits cap the amount of cut and fill, which on a steep lot determines whether a building pad can be created at all. Running this analysis during due diligence - rather than discovering the cumulative result during design - allows buyers to match their building program to the lot's actual capacity from the outset.

For a detailed explanation of how hillside construction regulations affect project planning and cost, see our Hillside Construction guide.

Geological and Geotechnical Due Diligence

What is under the lot matters as much as what the zoning code allows on top of it. The subsurface conditions of a building lot determine the foundation system required, the retaining wall systems needed, the grading approach, the drainage design, and ultimately a significant portion of the total construction cost. On hillside lots in Los Angeles, the geological conditions are the single largest variable in project cost.

The first step in geotechnical due diligence is reviewing whatever information already exists. Previous development attempts on the lot may have generated geotechnical reports that are available through LADBS records or from the listing agent. Adjacent property reports can provide useful information about regional soil and geological conditions. The California Geological Survey publishes geological hazard maps that identify landslide zones, liquefaction zones, and fault zones. ZIMAS overlays several of these hazard designations onto the parcel map. All of this information is available before you spend a dollar on new investigation.

If existing information is insufficient, a pre-purchase geotechnical evaluation provides direct data on subsurface conditions that affect foundation design and cost. A typical pre-purchase investigation involves a site reconnaissance by a licensed engineering geologist and geotechnical engineer, review of published geological maps and aerial photographs, limited subsurface exploration (one to three borings or test pits, depending on the site), laboratory testing of soil samples, and a report addressing site geology, soil conditions, slope stability, foundation recommendations, and any identified hazards.

The specific geological hazard designations that affect LA lots include Alquist-Priolo Earthquake Fault Zones, which prohibit construction of habitable structures across active faults and require fault rupture investigations (trenching) before permits are issued. Earthquake-Induced Landslide Zones, which identify areas where seismic shaking could trigger slope failures and require stability analysis. Liquefaction Zones, which identify areas where saturated sandy soils could lose bearing capacity during an earthquake and require densification or deep foundation solutions. And locally mapped landslide areas, which identify sites with historical or potential slope instability.

The "artificial fill" condition deserves specific attention. Before the city's 1963 grading ordinance, hillside lots throughout Bel Air, the Bird Streets, and parts of the Palisades and Hollywood Hills were graded and filled without modern engineering standards, without compaction testing, and without inspection. This pre-1963 uncertified fill may appear stable under a house that has sat on it for decades, but it is not suitable as bearing material for new construction under current code. When a new project is proposed, LADBS and the geotechnical engineer will require that uncertified fill either be removed and recompacted to current standards or bridged with deep foundations that bypass the fill and bear on competent native material below. Removing and recompacting fill on a hillside lot can cost $200,000 to $500,000 or more, depending on volume and site access constraints. Identifying fill conditions through a pre-purchase geotechnical evaluation allows this cost to be factored into the purchase decision and project budget from the start.

Evaluating existing retaining walls on a property is another critical component of geological due diligence. Retaining walls that appear sound on the surface may be structurally inadequate, lack drainage, or be built on failing foundations. On hillside lots, existing retaining walls are often the most expensive existing condition to address, with replacement costs ranging from $200,000 to $800,000 or more. Our Retaining Walls guide covers evaluation, engineering, and cost in detail.

Drainage evaluation on hillside lots should include assessment of surface water patterns (where does water go during a rain event?), subsurface water conditions (is there a perched water table or springs on the property?), and the adequacy of existing drainage infrastructure. Water is the most common cause of retaining wall failure and slope instability on LA hillside properties, and the drainage conditions you inherit with the lot will either need to be accommodated or corrected as part of any new construction.

For a detailed discussion of foundation systems, geotechnical engineering, and the cost implications of different soil conditions, see our Foundation Systems and Geotechnical guide.

Fire-Damaged Lots and PGRAZ Parcels

The January 2025 Palisades fire created a distinct category of lot due diligence that did not exist at this scale before. Thousands of fire-damaged parcels across Pacific Palisades, portions of Malibu, and the Santa Monica Mountains are now entering the real estate market, either as rebuild opportunities for original owners or as purchase opportunities for buyers willing to take on the complexity of fire-damaged site conditions. The due diligence requirements for these lots go beyond standard vacant lot evaluation.

Environmental contamination assessment is the first requirement. When a residential structure burns, it releases hazardous materials into the soil: lead from paint, asbestos from older building materials, heavy metals from appliances and electronics, volatile organic compounds from burned plastics and synthetic materials, and potentially more concentrated contamination from stored household chemicals, pesticides, and automotive fluids. The U.S. Army Corps of Engineers handled Phase 1 debris removal for federally designated disaster areas, which included removal of hazardous materials and contaminated soil. However, property-specific contamination may remain, particularly in areas where chemicals were stored, where ash and debris accumulated, or where contaminated runoff concentrated during rain events following the fire.

Buyers of fire-damaged lots should expect to commission or review a Phase I Environmental Site Assessment to evaluate the potential for residual contamination, and potentially a Phase II assessment (which includes soil sampling and laboratory analysis) if the Phase I identifies concerns. The cost of environmental assessment ranges from $3,000 to $15,000 or more depending on scope. If contamination is found that requires remediation, cleanup costs can range from modest (soil removal in a localized area) to substantial (widespread contamination requiring extensive excavation and disposal).

PGRAZ - Palisades Geohazard Risk Assessment Zone - designations were established by LADBS following the fire to identify geologically sensitive areas within the fire-affected zone. The PGRAZ map divides the affected area into two categories. Orange zones include sites on or next to steep slopes (generally steeper than 2:1, or 50 percent grade) or potential landslide areas. Yellow zones include sites at the bottom of steep slopes that are prone to being affected by mudslide debris. Properties within PGRAZ zones require combined geology and soil reports before rebuilding permits are issued.

The significance of a PGRAZ designation for a lot buyer is both regulatory and financial. On the regulatory side, the geology and soil reports required for PGRAZ properties add $15,000 to $50,000 or more in investigation costs, depending on the complexity of the site. On the financial side, the findings from those investigations may reveal conditions - active landslide potential, inadequate bearing soils, destabilized slopes due to loss of vegetation - that require significantly more expensive foundation and site stabilization systems than a non-PGRAZ property. For properties not identified on the PGRAZ map, LADBS recommends consulting a geotechnical engineer, as the absence of a PGRAZ designation does not guarantee the absence of geological concerns. For a comprehensive discussion of PGRAZ designations and fire rebuild requirements, see our PGRAZ Fire Rebuilds guide.

The insurance situation for fire-damaged lots is an important due diligence item. When purchasing a fire-damaged lot from an original owner, clarifying what insurance coverage (if any) remains on the property, whether any coverage transfers with the sale, and how pending insurance claims affect the transaction gives both parties a clear framework. Understanding the relationship between the insurance settlement, the sale price, and the rebuild cost allows the buyer to evaluate the total project economics accurately.

Utility status is another consideration specific to fire-damaged properties. The fire may have destroyed utility infrastructure - gas lines, electrical service, water connections, sewer laterals - that served the original home. Confirming what infrastructure was damaged, what has been restored, and what the reconnection timeline looks like during due diligence allows the buyer to align the project schedule with infrastructure availability. In the Palisades specifically, community-wide infrastructure reconstruction (underground utilities, road improvements, water system upgrades) is ongoing, and individual property rebuild schedules benefit from coordination with these improvement timelines.

The distinction between a "like-for-like" rebuild and new construction matters for both cost and timeline. Under the emergency executive orders issued following the fire, like-for-like rebuilds (roughly the same size, location, and use as the original structure, with up to a 10 percent increase in footprint and height) receive expedited permitting and fee waivers. Projects that exceed the like-for-like parameters are treated as new construction and go through the standard permitting process, which is significantly longer and more expensive. If you are purchasing a fire-damaged lot with the intent to build something substantially different from the original home, understand that you are entering the new construction permitting track. For detailed information on fire rebuild requirements, timelines, and costs, see our Fire Rebuild guide.

The Preliminary Title Report

The preliminary title report is standard in any real estate transaction, but most buyers review it for ownership and lien issues without evaluating how the recorded items affect future construction. On a buildable lot, the title report may contain items that fundamentally change what you can build and where you can build it.

Easements are the most consequential title items for construction planning. An easement grants someone other than the property owner the right to use a portion of the property for a specific purpose. The types of easements that commonly affect buildable lots in LA include utility easements (granting utility companies the right to install, maintain, and access infrastructure across a portion of the lot), access easements (granting adjacent property owners the right to cross your property to reach theirs), drainage easements (reserving a portion of the lot for water conveyance), view easements (restricting building height or placement to preserve a neighbor's view), and shared driveway easements (granting joint use of a driveway that crosses one or more properties).

A blanket easement across the rear ten feet of a lot, for example, means permanent structures are excluded from that ten-foot strip. Depending on the lot size and shape, that restriction affects the buildable footprint. A utility easement running diagonally across the property may influence building placement. A view easement may limit the height of structures on the lot to preserve a neighbor's sightline. Mapping these restrictions against the intended building program during due diligence confirms whether the lot's usable area supports the project scope.

CC&Rs (Covenants, Conditions, and Restrictions) and deed restrictions may impose additional development limitations beyond what the zoning code requires. In some Bel Air and Beverly Hills neighborhoods, CC&Rs restrict architectural styles, require minimum setbacks greater than the zoning code, limit building heights below the code-permitted maximum, or require homeowner association approval before construction. Deed restrictions recorded against the property by prior owners may limit development in ways that are not apparent from the zoning analysis.

Reciprocal easement agreements with neighbors are common on hillside properties where construction activities on one lot necessarily affect the adjacent lot. These agreements may grant tieback rights (allowing one property to install soil anchors that extend under the neighbor's property), temporary construction access rights, or shared maintenance obligations for retaining walls, drainage systems, or access roads. The presence or absence of these agreements can significantly affect construction feasibility and cost.

The survey is the essential companion to the title report. The title report tells you what encumbrances exist on paper. The survey tells you where they fall on the ground. A boundary and topographic survey is essential for any buildable lot purchase because it establishes the actual property lines (which may not match the fences, walls, or landscape features that appear to define the boundaries), locates all easements relative to the physical site, identifies any encroachments (structures or improvements that cross property lines), and provides the topographic data needed for slope analysis, building placement, and drainage design. The cost of a boundary and topographic survey ranges from $3,000 to $10,000 depending on lot size, terrain, and complexity.

Access, Utilities, and Infrastructure

A practical evaluation of whether a lot supports construction at a reasonable cost includes confirming that materials, equipment, and workers can physically reach the site and that the finished home can connect to essential services. On flat lots with standard street frontage, these are straightforward. On hillside lots throughout the Palisades, Bel Air, Malibu, and the Hollywood Hills, access and infrastructure are significant variables in the project budget, and quantifying them during due diligence provides clarity on the total project cost.

Construction access is the first evaluation. A custom home requires delivery of concrete (via concrete mixer trucks that weigh 60,000 to 80,000 pounds loaded), structural steel (via flatbed trucks), lumber and framing materials, heavy equipment including excavators and drill rigs, and a crane for steel erection and material placement on steep sites. Can these vehicles physically reach the lot? Many hillside streets in LA are narrow, winding, and steep, with limited turning radii and no room for truck staging. Substandard Hillside Limited Streets (a specific designation in the LAMC) impose additional setback and access requirements. Some hillside lots are accessible only by private roads, shared driveways, or easement access that may not support heavy construction traffic.

When construction vehicles cannot reach the site directly, the alternatives are expensive: pump trucks that extend concrete delivery over obstacles (adding significant cost to every pour), helicopter delivery of materials (used on some extreme hillside sites in Malibu and the upper Bird Streets), crane operations from a staging area below the lot, and hand-carrying materials up stairways or steep grades. On some projects, the construction access logistics alone add $300,000 to $500,000 to the total project cost.

Temporary construction access may require a neighbor's cooperation. If the lot is accessed through a shared driveway, or if construction staging, material storage, or equipment operation requires temporary use of adjacent property, securing that cooperation early simplifies the construction process. Establishing neighbor communication during due diligence - rather than after construction has started - gives both parties time to work through logistics and access arrangements.

Water service evaluation should include confirming that municipal water is available and that the pressure and capacity are adequate for a large residential structure. In some hillside areas, water pressure is insufficient for upper-floor fixtures and fire suppression without a booster pump system. The distance from the lot to the nearest water main, and whether a new service lateral needs to be installed, affects connection cost. In areas served by the Los Angeles Department of Water and Power (LADWP), a will-serve letter confirming service availability should be obtained during due diligence.

Sewer versus septic is a critical distinction. Most lots in the city-served areas of the Westside have access to municipal sewer, but some hillside lots and many properties in Malibu and unincorporated areas rely on private septic systems (technically Onsite Wastewater Treatment Systems, or OWTS). Septic system requirements in Malibu are particularly stringent under the city's Local Coastal Program, and the cost of a code-compliant advanced treatment OWTS system can exceed $100,000. The capacity of an existing septic system may also limit the size of the home you can build.

Electrical service capacity is relevant for large custom homes. A modern 5,000+ square-foot home with HVAC systems, pool and spa equipment, lighting, kitchen appliances, and EV charging can require 400-amp or even 600-amp electrical service. Confirming transformer capacity during due diligence is straightforward; if a transformer upgrade is needed through the utility provider, it typically costs $25,000 to $75,000 or more and takes months to schedule, so identifying the requirement early allows it to be incorporated into the project timeline.

The total cost of utility connections on hillside lots versus flat lots is one of the largest cost differentials in LA residential construction. On a flat lot in Brentwood with existing infrastructure at the street, utility connections might cost $15,000 to $30,000. On a hillside lot where the sewer main is 200 feet below the building pad and the water main is at the bottom of a steep access road, utility work can cost $100,000 to $300,000 or more. Confirming utility connection scope and cost during due diligence places this variable into the project budget early.

Tree Preservation and Environmental Constraints

Los Angeles's Protected Tree Ordinance (LAMC Section 46.00, as amended by Ordinance 177,404) protects several species of native trees that are common on hillside lots throughout the Westside. The protected species include all native oak trees (excluding scrub oak), Southern California black walnuts, Western sycamores, and California bay laurels that measure four inches or more in cumulative trunk diameter at 4.5 feet above grade. The ordinance defines "removal" broadly to include any act that causes a protected tree to die, including damage to the root system, application of toxic substances, operation of heavy equipment within the drip line, or changing the natural grade within the drip line area.

For lot buyers, the practical significance is this: when a protected tree is on or near the intended building footprint, the tree's protected zone (the area within five feet of the drip line, or 15 feet from the trunk, whichever is greater) constrains construction activity. Excavation for foundations within the protected zone requires a tree removal or impact permit, which involves approval from the Board of Public Works, public notice, an arborist report, and often mitigation in the form of replacement trees (typically at a ratio of 2:1 or greater) or a monetary contribution to the city's tree fund. Identifying protected trees during due diligence and mapping their protected zones allows the building footprint to be planned around them from the start.

The timeline for tree-related permitting can add three to six months or more to a project, and the cost of the arborist report, the permit process, and the required mitigation typically runs $10,000 to $50,000 depending on the number of trees affected and the complexity of the mitigation plan. In some cases, the presence of a large protected tree in the center of a buildable lot fundamentally constrains where the house can be placed, reducing the practical buildable area well below what the zoning code would otherwise allow.

In unincorporated LA County areas (including portions of the Santa Monica Mountains), the County's Oak Tree Permit Ordinance (County Code Chapter 22.174) applies similar protections with its own permitting process through the County Forestry Division. In Malibu, native trees are protected under the city's Local Coastal Program (LIP Section 5.2), which defines the protected zone and requires additional review and mitigation for any development activity within that zone.

Beyond trees, environmental constraints that can affect lot purchases include biological resources (sensitive habitat, threatened or endangered species) that trigger additional review under the California Environmental Quality Act (CEQA), streambed and riparian habitat on canyon lots that may be subject to California Department of Fish and Wildlife jurisdiction, and wetland areas that trigger Army Corps of Engineers jurisdiction. These constraints are most common on larger lots in canyon settings and along the coast, and identifying them during due diligence allows buyers to factor the additional permitting timeline and cost into project planning.

The Pre-Purchase Feasibility Assessment

A pre-purchase feasibility evaluation by a construction professional who builds on similar sites provides information that is difficult to obtain through other channels in the transaction. The evaluation draws on direct experience with the specific construction conditions - geological, regulatory, logistical, and financial - that determine project viability on a given lot.

A pre-purchase feasibility evaluation typically includes a site visit to assess physical conditions (slope, access, existing structures, vegetation, drainage, neighbor conditions), review of the ZIMAS regulatory profile, review of any available geotechnical information, preliminary buildable area assessment based on slope and zoning constraints, order-of-magnitude construction cost range for the type and size of project you are considering, identification of major cost drivers and constraints that may affect project scope, and a realistic estimate of project timeline from purchase through occupancy.

The cost of a pre-purchase feasibility evaluation ranges from $5,000 to $25,000 depending on scope. At the lower end, this covers a site visit, regulatory review, and a written assessment with preliminary cost and timeline ranges. At the higher end, it may include coordination with a geotechnical engineer for preliminary subsurface evaluation, a surveyor for boundary and topographic verification, and more detailed cost analysis.

The value of a construction-focused evaluation is that it identifies conditions that are specific to building on the site: access limitations for construction equipment, slope band calculations that limit floor area, retaining wall conditions that require replacement, sewer connections that require pump stations, and protected trees within the building footprint that add permitting time. These are construction variables that affect project cost and timeline, and evaluating them supplements the standard real estate transaction analysis with site-specific construction data.

Structuring the purchase contingency around a feasibility evaluation is straightforward. The standard California residential purchase agreement provides a contingency period (typically 17 days, though this is negotiable) during which the buyer can conduct investigations and cancel the contract if the findings are unsatisfactory. For a buildable lot, the contingency period should be long enough to complete at least a preliminary feasibility evaluation, which typically requires two to four weeks. Requesting a 30-day contingency for a vacant lot or teardown purchase is reasonable and common.

Findings that warrant careful evaluation of whether to proceed include conditions that limit the buildable area to a size substantially smaller than the intended project, geological conditions that indicate high foundation and site work costs (active landslide potential, deep uncertified fill, inadequate bearing capacity), access conditions that make construction logistics significantly more expensive, utility infrastructure that is unavailable or expensive to connect, environmental constraints that would extend the permitting timeline substantially, and a total project cost estimate (land + design + permitting + construction) that exceeds the project budget.

For a detailed discussion of what a formal feasibility evaluation includes and how it informs project planning, see our Feasibility Report guide.

Common Due Diligence Findings

Certain site conditions come up frequently enough in LA lot evaluations that they are worth describing in detail. Understanding these patterns helps buyers ask the right questions before committing.

Lots with limited practical buildability are parcels that are zoned residential and technically qualify as development sites, but where the combination of regulatory constraints, geological conditions, access limitations, and existing conditions makes practical construction significantly more complex or expensive than the lot's listing would suggest. In Bel Air, for example, a lot may carry an R1 zoning designation and a recorded lot number, while the slope band analysis limits the RFA to near the guaranteed minimum, the access road is a single-lane private easement, the lot falls within an Alquist-Priolo Fault Zone requiring a $60,000 trenching investigation, and protected oaks occupy the most viable building pad location. These overlapping constraints do not make the lot unbuildable, but they substantially affect what can be built and at what cost.

Constrained construction access is a condition where the logistics of getting materials and equipment to the site significantly affect project cost and feasibility. This includes lots accessed by narrow private roads with no truck turnaround, lots where access requires crossing a neighbor's property, lots at the bottom of steep driveways where there is no staging area for materials or equipment, and lots where the vertical difference between the street and the building pad requires crane operations for every material delivery. These conditions are common in the upper reaches of Bel Air, the canyons above Sunset in the Palisades, and the hillside streets above Malibu Colony.

Neighbor coordination requirements arise when a project requires something from an adjacent property owner: a tieback easement for retaining wall anchors, temporary construction access across their driveway, cooperation during shoring operations that affect their property, or acceptance of the visual and noise impacts of hillside construction. In some hillside neighborhoods, neighbor opposition has delayed projects through permit objections, construction complaints, and litigation. Evaluating the neighbor situation before purchase - shared walls, shared access, pending disputes, or known concerns about development - provides useful context for project planning.

Unanticipated environmental conditions include contamination, protected habitat, or other environmental factors that affect construction scope and cost. This is relevant for former agricultural land (pesticide contamination), lots adjacent to former commercial or industrial uses, lots in canyon settings with riparian habitat, and fire-damaged lots where combustion byproducts have affected the soil. Environmental remediation costs vary widely depending on the type and extent of contamination.

Utility connection cost differentials are most significant on hillside lots where the utility mains are far from the building pad, on lots that require septic systems rather than sewer connections, and on lots where the existing electrical infrastructure cannot support the load of a large modern home. Utility connection costs on hillside lots can exceed $300,000, compared to $15,000 to $30,000 on a flat lot with existing infrastructure at the street.

Floor area and height expectations benefit from early analysis on hillside lots. A buyer looking at a 15,000-square-foot lot can confirm the actual buildable area by running the slope band analysis, checking hillside ordinance requirements, specific plan restrictions, and overlay zone parameters during due diligence. Height limits on hillside lots are measured as an envelope that follows the slope, and the resulting building profile is worth modeling early. Intended uses (guest house, ADU, pool house) can be confirmed against the applicable regulations before the purchase is finalized.

Site work-intensive properties are lots where the site work - retaining walls, grading, foundations, shoring, utility connections, access improvements, tree mitigation, environmental remediation - represents a substantial portion of total project cost. On challenging hillside sites, a lot that requires $1,500,000 in site work before vertical construction begins changes the total project economics. The purchase price of the lot becomes a relatively small portion of the total investment, and understanding the site work scope before closing allows the buyer to evaluate the total project cost realistically.

Cost Context

The purchase price of a lot is the first component of the total project cost. Understanding the full cost structure during due diligence provides a framework for evaluating whether a lot makes financial sense for the intended project.

Pre-purchase due diligence costs, which are spent before you close, include a boundary and topographic survey ($3,000 to $10,000), a pre-purchase geotechnical evaluation ($5,000 to $15,000), a pre-purchase feasibility assessment by a construction professional ($5,000 to $25,000), and a Phase I Environmental Site Assessment if indicated ($3,000 to $8,000). Total pre-purchase investigation costs typically range from $10,000 to $50,000. This is a modest investment relative to the cost of the information it provides.

Design and permitting costs from lot purchase through building permit issuance include architectural design, structural engineering, civil engineering, landscape architecture, energy compliance, and permit fees. For a custom home in the $3M to $15M range in LA's Westside neighborhoods, design and permitting costs typically run 12 to 18 percent of construction cost, or roughly $400,000 to $1,500,000 for the design and engineering scope, plus permit fees that vary by jurisdiction. The permitting timeline from plan submission to permit issuance ranges from 6 to 18 months depending on project complexity, jurisdictional requirements, and whether discretionary approvals are needed.

Site work costs are the most variable component and the one most directly affected by the lot's conditions. On a flat lot with standard access, stable soils, existing utility connections, and no significant existing conditions, site work (grading, foundations, utility connections, and flatwork) might represent 10 to 15 percent of total construction cost. On a steep hillside lot with challenging access, poor soils, retaining wall requirements, and distant utilities, site work can represent 30 to 50 percent or more of total construction cost. The table below provides order-of-magnitude site work cost ranges by lot type.

Total construction costs in the LA luxury residential market currently range from approximately $600 to $1,200+ per square foot, depending on finish level, site complexity, and market conditions. These costs do not include land, design fees, or permitting. For a detailed breakdown of current construction costs by project type and component, see our Construction Costs guide. For information on how project timelines affect carrying costs and total investment, see our Construction Timeline guide.

The relationship between lot conditions and total project cost is the essential calculation: Purchase Price + Due Diligence + Design and Permitting + Site Work + Vertical Construction + Contingency = Total Project Cost. On a challenging hillside lot, the non-construction costs (land, design, permitting, site work) can represent 50 percent or more of the total investment. Building this calculation during due diligence provides a realistic picture of the total commitment the project requires.

Frequently Asked Questions

This page is published by Benson Construction Group, Inc., CSLB License #1007735. The information provided is based on professional experience managing residential construction projects in Los Angeles and is intended as general guidance. Specific project conditions vary. Code citations reference regulations in effect at the time of publication; verify current requirements with the applicable jurisdiction before making decisions. This page is not a substitute for professional consultation with a licensed contractor, engineer, geologist, or attorney for your specific situation.