Most California lots can take an ADU. The real question is rarely “am I allowed?” — it is which of three layers decides your specific parcel: state ADU law, the recorded paper on your title, or the physical conditions of the site itself. This guide walks all three, in the order a feasibility review actually checks them.
Here is the pattern that surprises most homeowners: state ADU law has a great deal to say about the house and almost nothing to say about the lot’s shape, trees, easements, or flood status. The words “easement,” “flag lot,” “corner lot,” “alley,” “hillside,” and “floodplain” do not appear in the California Department of Housing and Community Development’s ADU Handbook at all. What state law gives you instead is a floor that local zoning cannot go below — and an express rule that building, health, safety, and fire codes still apply in full. Everything in this guide follows from those two facts. This page is the Property Eligibility chapter of our California Accessory Dwelling Unit Handbook; when you want the checks run on your own parcel, that is exactly what our ADU Feasibility Report does.
The Two Tests Every Property Has to Pass
Test one — the legal test. An accessory dwelling unit is, by definition, a unit “located on a lot with a proposed or existing primary residence” (Government Code section 66313(a)). The lot must be zoned to allow single-family or multifamily dwelling residential use and include a proposed or existing dwelling (section 66314(d)(2)); the state-guaranteed pathways in section 66323 apply in a residential or mixed-use zone. Inside that frame, a city cannot use lot coverage, floor area ratio, open space, front setbacks, or minimum lot size rules to block an ADU of at least 800 square feet with four-foot side and rear setbacks (section 66321(b)(3)) — and no minimum lot size may be imposed at all (section 66314(b)(1)).
Test two — the physical test. Section 66314(d)(8) requires ADUs to comply with the local building code requirements that apply to detached dwellings. State ADU law caps local zoning standards; it does not waive soils reports, slope rules, fire access, or floodplain construction standards. A lot passes eligibility when it clears both tests — the zoning floor gets you the right to build, and the codes decide how the building has to sit on the land.
| Question about your lot | Decided by | The short answer |
|---|---|---|
| Is my zoning right? | Gov. Code §§66314, 66323 | Residential or mixed-use zoning with a proposed or existing dwelling is the frame; purely commercial/industrial zoning is outside the ADU guarantee |
| Is my lot big enough / the right shape? | Gov. Code §66321(b)(3) | No minimum lot size; shape rules cannot preclude the 800 sq ft / 4-foot unit |
| Can I build in the easement? | Your recorded title documents + Civil Code §§801–813 | ADU law is silent — a permit does not override an easement; the holder’s consent is the gate |
| Can CC&Rs stop me? | Civil Code §§4751, 714.3 | Provisions that effectively prohibit or unreasonably restrict an ADU on a single-family lot are void; reasonable restrictions survive |
| Do I need a survey? | Local checklist + Bus. & Prof. Code §8726 | State ADU law does not require one; some cities do — and only a licensed surveyor can legally establish your lines |
| Slope, flood, trees, fire access? | Building/fire codes + local ordinances (§66314(d)(8)) | Fully in force — ADU approval does not waive any of them |
Zoning and the House: The Eligibility Basics
Zoning designation
A city’s ADU ordinance designates where ADUs may be permitted, and state law limits the bases for drawing that map: the designation “may be based on the adequacy of water and sewer services and the impact of accessory dwelling units on traffic flow and public safety” (section 66314(a)). HCD is explicit that a city may not preclude ADUs altogether, and the section 66323 guaranteed units cannot be designed away by local map-drawing. Two practical consequences. First, check the parcel’s actual zoning on the city’s map — a lot that has been rezoned to a use that does not allow residential use is no longer ADU-eligible, per HCD. Second, mixed-use zones that allow dwellings sit inside the section 66323 guarantee even though the ordinance path in section 66314 speaks of single-family and multifamily residential use — if your lot is mixed-use, the permit counter’s first answer is not necessarily the last word.
Existing residence status: proposed counts
The primary dwelling does not have to exist yet. “Proposed dwelling” is a defined term: a dwelling “that is the subject of a permit application and that meets the requirements for permitting” (section 66313(l)). If you file for a new house and an ADU together, the city may hold the ADU decision until it decides the house application — but the ADU is still considered ministerially, without discretionary review or a hearing (section 66317(a)(3)). State law also imposes no requirement that the primary home be occupied, owner-occupied, or already issued a certificate of occupancy before you apply for the ADU.
Vacant parcels: the honest no — and the way around it
There is no standalone-ADU-on-a-vacant-lot pathway in California ADU law. The word “vacant” never appears in HCD’s Handbook, and every pathway in sections 66314 and 66323 is keyed to a proposed or existing dwelling. An intention to build a house someday is not a “proposed dwelling” — the permit application is what makes it proposed. So the vacant-lot route is a combined project: house application and ADU application filed together, reviewed concurrently. The pitfall to avoid is sequencing it backwards: build the ADU first on a promise, and if the house application is later withdrawn or denied, the unit is left with no primary dwelling and no basis in ADU law. (A vacant single-family lot has a separate, non-ADU route under SB 9 — see our SB 9 lot splits guide.)
Multifamily Lots: Eligibility at Apartment Scale
Multifamily properties run on two section 66323 pathways, and they stack. Conversions (section 66323(a)(3)): a city must allow at least one ADU, and up to 25 percent of the existing units, created inside portions of an existing multifamily structure that are not livable space — storage rooms, boiler rooms, passageways, attics, basements, and garages are the statute’s own examples — as long as each unit meets state building standards for dwellings. (State law does not state a rounding rule for fractional results, so an odd count is a confirm-at-intake question, not a number to assume.) Detached units (section 66323(a)(4)): on a lot with an existing multifamily dwelling, up to eight detached ADUs — but never more than the number of existing units; on a lot with a proposed multifamily dwelling, up to two. The detached units take four-foot side and rear setbacks, and if the existing building already sits closer than four feet, the city cannot force you to modify it as a condition of approval. HCD treats a structure with two or more attached dwelling units on one lot as a multifamily dwelling (multiple detached houses on one lot are not, for ADU purposes). One hard limit: junior ADUs are a single-family tool — section 66333 confines JADUs to single-family lots, so there is no JADU on a multifamily parcel. Worked examples: a 4-unit building supports up to 1 conversion plus up to 4 detached units; a 20-unit building supports up to 5 conversions plus 8 detached (the eight-unit cap binds). Our California ADU law hub covers SB 1211, the bill that set these numbers.
Odd-Shaped Lots: Irregular, Corner, Flag, and Alley Lots
State ADU law contains no lot-shape category at all — no definition of an irregular lot, no flag-lot rule, no corner-lot setback, no alley standard. That silence is mostly good news, because the test that replaces shape rules is outcome-based: can the guaranteed unit — at least 800 square feet with four-foot side and rear setbacks — be built on this parcel? If a city’s coverage, open-space, or front-setback rules would make that impossible on an odd-shaped lot, section 66321(b)(3) says those rules cannot be applied to that extent. What shape actually changes is geometry and cost, not eligibility.
Irregular lots
On a wedge, L-shaped, or pie-shaped parcel, the feasibility work is drawing, not law: offset every side and rear lot line by four feet and see what envelope remains, then check fire separation and building-code clearances against the house and the neighbors. An unusual shape does not need a variance and does not earn extra size or height relief — it simply moves where the envelope lands. Some cities define buildable-area or average-width rules for the primary house in their zoning codes; ask the city how its code treats your parcel’s shape rather than assuming a statewide answer.
Corner lots
A corner lot’s wrinkle is that two yards face streets, and many local codes treat both as front yards. Front setbacks are the one setback a city may apply to a standard ADU — but per HCD, a front setback cannot be applied so as to preclude an 800-square-foot ADU, even if that unit would sit partly or wholly within the front setback; and a section 66323 state-guaranteed unit is not subject to local front setbacks at all. Which yard your city calls the “front” is a local-code definition, so confirm it before the site plan is drawn. Corner visibility and driveway-clearance rules, where they exist, are local public-works standards — check them locally, because no state ADU rule sets them.
Flag lots
A flag lot — a rear parcel reached by a narrow access strip — is a creature of local zoning and subdivision practice; state ADU law neither blesses nor bans it. Two state rules do touch the fact pattern: a city may not require a “passageway” from the street to the ADU’s entrance as a condition of approval (section 66314(d)(6)), and the four-foot / 800-square-foot floor applies on a flag lot exactly as on any other. What actually decides a flag-lot project is access in the physical sense — whether fire apparatus can reach the rear unit under the Fire Code (below) — plus longer utility runs down the pole and local addressing for a unit that does not face the street. State law also does not create or enlarge any right to cross a neighbor’s land: if the strip is an easement, its recorded terms govern (next section).
Alley access
Nothing in ADU law requires, forbids, or regulates alley access — an alley-facing entrance or an alley-loaded garage conversion is a design and title question, not an ADU-law question. The governing layer, when the alley is the access route, is the California Fire Code: fire apparatus access roads must extend to within 150 feet of all portions of a building, with an unobstructed width of at least 20 feet and vertical clearance of at least 13 feet 6 inches, an approved turnaround on dead-ends over 150 feet, and grades set by the local fire official (Fire Code section 503). Many residential driveways are administered under local fire-district driveway standards rather than the full road standard, so the practical step is to ask the fire district how it treats your alley — and to confirm on the title report and city map whether the alley is public, private, or an easement, because that decides who may use it and who maintains it.
Slopes and Hillsides: Where the Building Code Takes Over
There is no slope percentage anywhere in state ADU law — no cutoff above which an ADU is prohibited, and no exemption from soils work because the project is an ADU. Sloped and hillside parcels are governed by the California Building Code’s soils and foundations chapter, which section 66314(d)(8) keeps fully in force. Under Building Code section 1803, a geotechnical investigation is required when the investigated conditions in section 1803.5 are present — questionable or expansive soil, compacted fill under footings, excavation near existing foundations, and seismic evaluations that expressly include slope instability — and the local building official can waive the investigation where satisfactory data from adjacent areas shows it is unnecessary, or require one where the site raises concerns. In practice, sloped lots are where those triggers most often fire, so budget for a soils report on a hillside project rather than hoping to skip one.
Foundation placement has its own slope geometry. For slopes steeper than one vertical in three horizontal (a 33.3 percent slope), Building Code section 1808.7 — and its Residential Code counterpart, section R403.1.7, for dwellings under that code — sets clearances measured from the slope itself: the standard geometry works out to a building clearance of half the slope height (capped at 15 feet) from an ascending slope, and a footing setback of one-third the slope height (capped at 40 feet) from a descending slope, unless a geotechnical investigation supports an alternate. On a steep lot, that slope geometry — not the four-foot lot-line setback — is often the tighter constraint, and it is checked in addition to the zoning setbacks, not instead of them.
Hillside overlays are local law. Los Angeles, for example, maps Hillside Areas and a separate Hillside Grading Area, and its hillside rules regulate height, yards, fire protection, lot coverage, parking, street access, sewer connections, and grading (Municipal Code sections 12.03, 12.21, 12.21.1 and 91.7003, among others). The state zoning floor still applies to a hillside lot — local zoning limits cannot preclude the guaranteed 800-square-foot unit — but a hillside provision that is a building, grading, or fire-code requirement is preserved by section 66314(d)(8), and how any specific hillside rule is classified is a parcel-specific question for the city (and, if it comes to it, HCD). Two more hillside realities to check early: additional ignition-resistant construction standards can apply in mapped fire-hazard severity zones, and hillside streets are exactly where Fire Code access questions concentrate. Our cost guide covers what slope does to foundation and retaining budgets.
Easements and CC&Rs: The Paper Layer on Your Title
Easements generally
State ADU law says nothing about easements — the word appears nowhere in the ADU statutes or HCD’s Handbook. That means a ministerial ADU approval does not override, move, or extinguish a recorded easement, and it confers no right to build inside one. Easements live in general California property law: an easement is a burden on one parcel (the servient tenement — usually your lot) for the benefit of another parcel or a holder such as a utility company (Civil Code sections 801–803), its scope “is determined by the terms of the grant” (section 806), the holder can sue to enforce it (section 809), and it is extinguished only by merger, destruction, the holder’s own act or assent, or disuse for the prescriptive period (section 811) — building an ADU is not on that list. The working sequence is therefore a title sequence: pull a preliminary title report, plot every recorded easement on the site plan, design the ADU outside the easement areas, and if any part of the project — footings, eaves, utility runs, access — must touch an easement, get the holder’s written consent before plan check, not after. Pinning down where an easement’s lines actually lie on the ground is licensed survey work (Business and Professions Code section 8726).
Utility easements
A utility easement is typically held by the company itself (an easement in gross, Civil Code section 802) for water, sewer, drainage, power, or communications lines, in whatever width and on whatever terms the recorded grant states. No ADU statute lets a city waive a utility’s easement or forces a utility to accept a structure inside it — and do not confuse the two subjects: the ADU chapter’s utility rules (section 66311.5) govern connections and fees, not easements. Expect the holder’s own clearance process, expect “keep the easement clear of structures” language in the grant, and treat a structure placed inside a utility easement without consent as exposed to a holder demand to remove it. Read your grant; the recorded document, not a rule of thumb, sets the clearance.
Access easements and shared driveways
An access easement is a right-of-way (Civil Code section 801(4)). Maintenance is codified: the owner of a private right-of-way easement, or of land it is attached to, must maintain it in repair, and absent an agreement the cost is shared in proportion to use (section 845). Nothing in ADU law expands an easement’s scope for an ADU’s occupants — whether your tenants and guests may use a shared drive under the existing grant is a question the grant’s own words answer, which is why an ADU whose only street access runs over an access easement deserves a title-and-attorney read of that grant before design money is spent. (One nearby rule is not an easement rule: section 66314(d)(6)’s bar on requiring a passageway limits what a city can demand on your own lot; it creates no rights across anyone else’s.)
Recorded covenants and CC&Rs
California voids the CC&R clauses homeowners fear most. Under Civil Code section 4751(a), a covenant, restriction, or governing-document provision in a planned development that “effectively prohibits or unreasonably restricts” an ADU or JADU on a lot zoned for single-family residential use — where the unit meets state ADU law — is void and unenforceable. Section 714.3 applies the same voiding rule to recorded covenants on ordinary lots outside a common-interest development. Both statutes preserve reasonable restrictions, defined by a three-part test: a restriction survives unless it unreasonably increases construction cost, effectively prohibits construction, or extinguishes the ability to build the unit (sections 4751(b), 714.3(b)) — and under section 714.3(b), reasonable restrictions cannot include fees or other financial requirements. HCD’s examples of effective prohibition include review delays beyond the state’s 60-day timeframe, forced permit re-application, neighbor-approval conditions, and placement restrictions that make the unit infeasible; reasonable design standards (materials, architectural style) applied within reason are the kind that survive. Two limits to keep straight: both statutes are written for single-family-zoned lots, and whether a specific clause crosses the line is a fact-specific call — the statutes give you the test, and our FAQ covers the related HOA question.
Property Lines, Surveys, and Encroachments
Property lines: every setback is only as good as the line
State ADU law measures its core standards from your lot lines — four feet “from the side and rear lot lines” (section 66314(d)(7)) — but it never tells you where those lines are, and an ADU permit does not validate a structure’s position against the true line. A fence, a block wall, a county GIS printout, and an assessor’s parcel map are all evidence people rely on; none of them is the legal line, and adjoining owners share responsibility for maintaining the boundaries and monuments between them (Civil Code section 841(a)). The risk math is simple: an ADU designed hard against the four-foot setback carries the full risk of any line error — if the assumed line is off by a foot, the built unit is a three-foot-setback structure, and possibly an encroaching one.
Boundary surveys: not state-required, often decisive
No provision of state ADU law requires a boundary or topographic survey as a condition of an ADU permit — HCD mentions property surveys only as an eligible predevelopment cost under a grant program. But two qualifications matter. First, locating, establishing, or retracing “any property line or boundary of any parcel of land, right-of-way, easement” is the statutory definition of land surveying (Business and Professions Code section 8726), reserved to licensed land surveyors (and civil engineers authorized to practice surveying) under section 8725 — so if the line needs establishing, only a licensee can legally do it. Second, cities can and do require survey information in their submittal checklists: Newport Beach’s ADU checklist, for example, requires a boundary survey or markers on site for all detached new construction, may require a survey on sloping ground, and always requires one for new detached construction in a Special Flood Hazard Area. When a field survey discloses discrepancies or sets new boundary points, the surveyor must file a Record of Survey with the county within 90 days (section 8762) — that filing duty is the surveyor’s, not the homeowner’s, and it is not a permit condition. Practical guidance: commission the survey before design is finalized whenever the ADU will sit at or near the minimum setback, the lot is irregular or sloped, fences visibly wander, or records conflict. It is the cheapest insurance in the entire project.
Encroachments: a permit does not cure a crossing
If an existing structure — a garage, a wall, a fence — already crosses a property line, or a neighbor’s structure crosses onto your lot, there is no ADU rule for that: the Handbook never uses the word. An ADU permit neither legalizes an existing encroachment nor protects a new one, and the city has no power to settle a private boundary dispute as part of plan check. An action for trespass on real property carries a three-year limitations period (Code of Civil Procedure section 338(b)), but how deadlines and the case-law doctrines around long-standing crossings apply is intensely fact-specific — delay can change the available remedies, and this is attorney territory, not a self-help calculation. The safe sequence is practice, not law: survey first, so you know whether anything actually crosses and by how much; do not design the new ADU on top of an unresolved crossing; resolve it on paper (a recorded easement, a lot-line adjustment, a written agreement, or removal) with a real-estate attorney’s advice; and never assume that because a crossing “has been there for years,” it has been cured.
What’s Already on the Lot: Unpermitted Work, Sheds, and Garage Placement
Unpermitted additions
Sort the unpermitted work on your lot into two piles, because the law treats them very differently. Pile one: an unpermitted ADU or JADU built before January 1, 2020. Section 66311.7 (the AB 2533 law) bars a city from denying a legalization permit for such a unit based on building-code or ADU-law noncompliance — unless correcting the violation is necessary under the substandard-building standards of Health and Safety Code section 17920.3, or the building is deemed substandard. The city must publish its substandard-conditions checklist, you may get a confidential third-party code inspection first, and impact and connection fees are barred except where utility work is needed for health and safety. A separate route, section 66331, lets an owner request a five-year delay of enforcement for qualifying older units. Pile two: everything else — an unpermitted room addition, enclosed patio, or extra bedroom that is not an ADU gets no section 66311.7 protection and is handled under ordinary retroactive permitting. But pile two rarely blocks pile three: under section 66322(b), a city cannot deny a new ADU application because of unpermitted structures or code violations elsewhere on the lot that do not threaten public health and safety and are not affected by the ADU construction. Our permit process guide walks the legalization steps in full.
Existing sheds and other accessory structures
Yes, a shed can be the starting point: an “accessory structure” is simply a structure accessory and incidental to the dwelling on the same lot (section 66313(b)), and HCD says expressly that conversion of “detached garages, sheds, and other existing detached accessory structures” into ADUs is permitted by state ADU law (sections 66314(d)(3), 66323(a)(1)). The conversion pathway allows an expansion of up to 150 square feet beyond the structure’s existing dimensions, limited to accommodating ingress and egress; the unit needs exterior access independent of the house, and side and rear setbacks sufficient for fire and safety (section 66323(a)(1)). Conversions are not subject to unit-size requirements — and state ADU law sets no minimum size for the existing structure. The honest caveats: the structure must already exist (a shed you plan to build is new construction, judged under the detached rules); a JADU cannot be created in a detached shed, because a JADU must sit within the walls of the single-family residence itself (section 66333(d)); whether an unpermitted shed qualifies as the existing structure is a confirm-at-intake question; and most small sheds fail dwelling standards as they stand — no foundation, low ceiling, no insulation or utilities — because a conversion must meet all applicable building, health, safety, and fire standards for a dwelling. The zoning barrier is removed; the habitability work is not.
Garage placement: conversions keep their footprint rights
Where your garage already sits is protected when it becomes an ADU. “No setback shall be required for an existing living area or accessory structure or a structure constructed in the same location and to the same dimensions as an existing structure” that is converted to an ADU (section 66314(d)(7)) — so a garage conversion, or a demolish-and-rebuild in the same footprint at the same dimensions, carries no required setback even if the garage sits on or inside the four-foot line. On the section 66323 conversion path, the formulation is that side and rear setbacks be “sufficient for fire and safety” (section 66323(a)(1)(C)) — which is why fire-separation construction at the property line can still be required by the building code even though no zoning setback applies. Two companion rules: a demolition permit for a detached garage being replaced with an ADU must be reviewed with, and issued at the same time as, the ADU application (section 66314(e)), and when a garage or other parking structure is converted or demolished for an ADU, the city cannot require the lost off-street parking to be replaced (section 66314(d)(11)). Our garage conversion guide covers the build itself.
Trees and Floodplain: The Two Local Layers That Bite
Protected trees and roots
There is no state ADU tree rule — the nearest hook is that section 66314(b)(1) lets a local ordinance impose objective landscape standards, which is state law contemplating local regulation, not creating it. Tree protection exists only where a city or county has enacted it, and where it exists it runs alongside the ministerial ADU permit as a separate local permit. Los Angeles illustrates the pattern: its Protected Tree ordinance (Municipal Code section 46.00 and following) covers oaks, Southern California black walnut, western sycamore, and California bay measuring four inches or more in cumulative diameter at four and a half feet above the ground, and removal or relocation requires a city permit. Unincorporated Los Angeles County’s oak tree permit has long required a permit to cut, remove, or even encroach into the protected zone of an oak eight inches or more in diameter — the protected zone being the area within the dripline plus five feet beyond it, or 15 feet from the trunk, whichever is greater (the county was revising that ordinance in 2025, so confirm the current Title 22 chapter 22.174 thresholds before relying on them). Many jurisdictions have an oak or heritage-tree ordinance; many have none — pull your own city’s protected list and size threshold before assuming any tree on the lot is, or is not, regulated. For a tree that stays, root protection during construction is arborist practice rather than statute: fence at or beyond the dripline, keep trenching, grade changes, and material storage out of the fenced zone, and remember that foundation excavation and the sewer trench to the street are the usual root-damage events on an ADU job. Moving the ADU footprint a few feet is usually cheaper than a protected-tree fight — a feasibility observation our crews make often.
Floodplain constraints
ADU law does not waive floodplain rules, and there is no flood provision anywhere in the ADU statutes. What governs is your community’s floodplain ordinance — the local law every community in the National Flood Insurance Program must adopt and enforce to stay eligible for flood insurance, built on the federal minimums in 44 CFR section 60.3. The minimums that decide an ADU in a mapped flood zone (Zone AE is the common case): the lowest floor, including any basement, of a new or substantially improved residential structure must be elevated to or above the base flood elevation shown on the Flood Insurance Rate Map (section 60.3(c)(2)) — and note the asymmetry: dry-floodproofing instead of elevation is an option the federal text gives non-residential buildings, not homes. Any fully enclosed area below that lowest floor (parking, access, storage only) needs flood openings that let water in and out automatically — at least two openings, with total net area of at least one square inch per square foot of enclosed area, and the bottom of each opening no higher than one foot above grade (section 60.3(c)(5)). In a designated floodway, encroachments including fill and new construction are prohibited unless a hydrologic and hydraulic analysis shows the project would cause no increase in flood levels (section 60.3(d)(3)); before a floodway is designated, the limit is a cumulative rise of no more than one foot (section 60.3(c)(10)). Your city’s ordinance may be stricter than these federal floors — added elevation above the base flood level is the common example — so the city’s floodplain administrator, not the federal text, gives the final numbers. Mechanically: check the FIRM panel for your address (zone, base flood elevation, panel date), expect to document the finished floor with an Elevation Certificate signed and sealed by a licensed surveyor, engineer, or architect, and if the home carries a federally backed mortgage in a Special Flood Hazard Area, expect flood insurance to be required by the lender framework — confirm with your lender. Whether a garage conversion in a flood zone counts as a “substantial improvement” triggering the elevation rule is the local floodplain administrator’s determination; ask before designing, not after.
The Eligibility Checklist, in Order
- Zoning and dwelling: confirm the parcel’s zone allows single-family or multifamily residential use (or is residential/mixed-use), and that a primary dwelling exists or is being applied for (§§66313(a), 66314(d)(2)).
- Pathway and count: single-family conversion + detached + JADU, or the multifamily conversion/detached formulas (§66323) — and if the lot is vacant, file house and ADU together.
- The floor test: plot the 800-square-foot unit with four-foot side and rear setbacks against every local coverage, FAR, open-space, and front-setback rule (§66321(b)(3)); conversions keep their existing footprint (§66314(d)(7)).
- Title report: plot every easement; read CC&Rs against Civil Code sections 4751 and 714.3; confirm access rights where a shared drive or alley is the route in.
- Lines: if the design sits near a minimum setback, or records conflict, commission a licensed boundary survey (Bus. & Prof. Code §8726) before design is final.
- Site conditions: slope and soils triggers (Building Code §1803), slope setbacks (§1808.7 / CRC R403.1.7), hillside and fire-hazard overlays, fire access (Fire Code §503).
- Existing structures: inventory what is on the lot — unpermitted units (§66311.7), unrelated unpermitted work (§66322(b)), sheds and garages as conversion candidates (§66323(a)(1)).
- Trees and water: your city’s protected-tree list and thresholds; the FIRM panel, flood zone, and base flood elevation; the floodplain administrator’s local numbers.
Run in that order, eligibility stops being a guess. That sequence is, item for item, what our ADU Feasibility Report works through for a specific parcel — or start with a free consultation and bring us the address.
Send us the address. We will run the zoning, title, and site checks in this guide against your parcel and tell you straight what can be built, where it can sit, and what will try to stop it.
Call 888-627-1131 Get a Free ConsultationSources (verified November 2026): California Department of Housing and Community Development, Accessory Dwelling Unit Handbook, March 2026 edition (66323 Units, Multifamily, Zoning, Setbacks, HOA, and Unpermitted Structures sections); Government Code Sections 66311.5, 66311.7, 66313, 66314, 66315, 66317, 66321, 66322, 66323, 66331, and 66333; Civil Code Sections 801–813, 841, 845, 4751, and 714.3; Business and Professions Code Sections 8725, 8726, and 8762 (Professional Land Surveyors’ Act); Code of Civil Procedure Section 338(b); California Building Code Sections 1803, 1803.5, and 1808.7 and California Residential Code Section R403.1.7; California Fire Code Section 503; 44 CFR Sections 59.22, 59.24, and 60.3 (National Flood Insurance Program minimums); Los Angeles Municipal Code Sections 46.00 et seq. (protected trees), 12.03, 12.21, 12.21.1, and 91.7003 (hillside), and Los Angeles County’s oak tree ordinance (Title 22, chapter 22.174, in revision — confirm current thresholds). Where this guide describes survey, arborist, or design practice, it is labeled as practice in the text; parcel-specific rules are confirmed with the local jurisdiction. This page is part of the California Accessory Dwelling Unit Handbook on this site (Property Eligibility, Questions 101–150). Related: ADU FAQs · Size & Setback Rules · ADU Permit Process · ADU Feasibility Report
