ADU Permits Live at the Intersection of State Law and Local Zoning — and the Site Plan Has to Navigate Both
More states have passed ADU-enabling legislation in the last five years than in the prior fifty. What that means practically: your state may have overridden some of your city's ADU restrictions, but your city's permit desk is still running the application through its local checklist. The site plan has to satisfy what the local reviewer is looking for, using the state rules where they apply. We know the difference. From $159.
California passed AB 68 and SB 13 in 2020, dramatically loosening local ADU restrictions — reducing setbacks, eliminating minimum lot size requirements, capping impact fees, and restricting cities from requiring owner-occupancy on many ADU configurations. Texas passed HB 1115 in 2023, limiting HOA authority to prohibit ADUs. Florida, Oregon, Washington, and a growing list of states have moved in the same direction at different speeds.
The intent is to increase housing supply. The practical result is that homeowners applying for ADU permits are now working in a regulatory environment where state law and local ordinance exist in tension — and the local permit desk is still the entity processing the application.
A site plan for an ADU permit has to be drawn against the rules that actually apply after that tension is resolved. In California, that might mean state-mandated 4-foot rear and side setbacks rather than the city’s prior 5-foot minimum. In a Texas city whose HOA tried to restrict ADUs before HB 1115, the plan may need to reference the state preemption to move the application forward. Getting this wrong — drawing the plan against the local ordinance where state law has superseded it, or claiming a state exemption that doesn’t apply to the specific ADU configuration — produces either an unnecessarily constrained plan or a correction letter.
This is why ADU permits are more jurisdictionally specific than any other residential permit type. And why the site plan is the document where that specificity actually shows up.
Types of ADU — What You're Building Changes What the Plan Needs to Show
Detached New Construction ADU
A freestanding structure built separately from the primary dwelling. Requires the same lot boundary and setback work as a detached garage addition, but adds ADU-specific elements: separation distance from the primary dwelling, parking layout where required, utility connection routing, and in many jurisdictions a note designating the structure as a dwelling unit rather than a storage structure or workshop.
Garage Conversion ADU
Converting an existing attached or detached garage into a habitable dwelling unit. The footprint already exists on the lot, which simplifies the coverage calculation — conversion doesn’t increase the footprint. What changes: the structure’s classification shifts from accessory to dwelling, which affects setbacks, fire separation requirements, and sometimes triggers a separate utility connection review.
The site plan for a garage conversion needs to show the existing garage footprint and its current relationship to property lines, the proposed designation change, and any exterior modifications (new door or window locations, egress window placement) that affect the zoning picture.
Junior ADU (JADU)
A junior ADU is contained entirely within the walls of the primary dwelling — typically a converted bedroom, basement suite, or portion of a larger house, with its own exterior entrance and a kitchenette. JADUs are carved out of the existing structure rather than added to it.
Site plan requirements for JADUs are lighter than for detached ADUs or garage conversions, because the footprint doesn’t change. Most jurisdictions require the plan to show the primary dwelling footprint with the JADU location indicated, the exterior entrance location, and any utility separation notes. The complexity is in the building code compliance, not the site plan — but the site plan still has to exist.
Attached Addition ADU
An addition to the primary dwelling that creates a self-contained unit — its own entrance, bathroom, and kitchen — physically connected to the main house. Treated differently from a detached ADU in most zoning codes, often with the same setback requirements as the primary dwelling addition. The site plan has to show the addition footprint integrated with the existing house, all dimensions to property lines, and the entrance location.
What an ADU Permit Site Plan Has to Show
Separation Distance Between Primary Dwelling and ADU
One of the most commonly missed elements on ADU site plans submitted by homeowners. Most jurisdictions require a minimum separation between the primary dwelling and a detached ADU — typically 6 to 10 feet measured exterior wall to exterior wall, though some measure from the eave and some from the foundation. The plan needs to show this dimension explicitly.
Parking Layout
ADU parking requirements are in active flux across the country. Many states have eliminated parking requirements for ADUs within a certain distance of public transit. California eliminated parking requirements for ADUs entirely in most circumstances. Other states still require one additional off-street space per ADU unit.
Where parking is required, the plan needs to show the existing parking spaces, the proposed ADU parking space, its dimensions, and how vehicles access it. Where parking is explicitly exempted by state law, noting the exemption on the plan can prevent the reviewer from flagging it as missing.
Utility Connection Plan
ADUs need water, sewer, and electrical connections. How those connections are made — whether the ADU connects to the existing service lines as a branch, whether separate meters are required, and whether the existing service capacity supports the addition — varies by jurisdiction and by utility provider.
Most ADU permit site plans require at minimum a schematic showing how the ADU connects to water and sewer. Some jurisdictions require a licensed plumber’s or engineer’s input on this element specifically — not on the site plan itself, but as a separate utility exhibit. We note this where required so you’re not surprised when the permit desk asks for it.
Setbacks — State vs. Local
Where state preemption applies, the setback on the plan reflects the state-mandated minimum rather than the local ordinance’s prior requirement. Where it doesn’t, the local requirement applies. The plan has to use the right number, with a note indicating the legal basis if state law is being applied over a conflicting local rule.
Drawing the plan to the wrong setback — whether too restrictive because the drafter used the old local rule, or too permissive because the drafter assumed state preemption applies when it doesn’t for that ADU type — produces either a plan that wastes buildable space or one that comes back with a setback correction.
Owner-Occupancy Notation Where Required
Some jurisdictions still require the property owner to occupy either the primary dwelling or the ADU as their primary residence. Where this requirement exists and hasn’t been preempted by state law, the permit application typically includes an owner-occupancy declaration, and the site plan may need to reflect which unit is designated as owner-occupied.
Where state law has eliminated the owner-occupancy requirement, noting the applicable statute on the plan or in the application can move things past a reviewer who is still applying the old local rule from habit.
Fire Separation and Egress
Attached ADUs and garage conversions frequently require the plan to show fire-rated wall locations, egress window dimensions, and exit door locations. These are building code elements that overlap with the site plan when the reviewer is checking whether the proposed ADU configuration meets both zoning and life safety standards simultaneously.
The ADU Site Plan in States With Active Preemption Laws
If your property is in California, Texas, Oregon, Washington, Florida, or another state that has passed ADU-enabling legislation, the regulatory picture is different than it was five years ago — and different again from what your neighbor experienced when they tried and failed to get ADU approval under the prior rules.
California is the furthest along: state law now mandates ministerial approval for many ADU configurations, meaning local jurisdictions cannot use discretionary review to deny a compliant ADU application. The site plan for a California ADU needs to be built to the state’s standards specifically so the application can proceed on the ministerial track rather than getting routed into a discretionary review process with its own timeline and uncertainty.
Texas, by contrast, limits HOA authority over ADUs but doesn’t preempt local zoning rules wholesale. An ADU in a Texas city with its own ADU ordinance still gets reviewed under that ordinance — the HOA can’t block it, but the city’s setback, size, and parking rules still apply.
Knowing which state preemption framework applies to your property, your ADU type, and your local jurisdiction before drawing the plan is what separates a site plan built for how the rules actually work right now from one built for how they worked in 2019.
Does an ADU Permit Site Plan Need a Professional Stamp?
For the site plan itself — the zoning compliance document showing the ADU location, setbacks, and lot configuration — a non-certified drawing is what most jurisdictions accept. For structural drawings, electrical plans, and plumbing schematics, licensed professional involvement is more commonly required, and varies by jurisdiction and by ADU type.
Some California jurisdictions specifically require certain ADU configurations to go through a licensed architect or designer for the building plans. That requirement applies to the building plans, not the site plan.
We produce non-certified site plans for ADU permits in municipalities that accept them for zoning review. If your jurisdiction’s site plan requirement specifically calls for a surveyor’s stamp or engineer’s seal, we’ll flag that before you order rather than after.
Pricing
Detached New Construction ADU Site Plan — $159 Lot boundaries, separation distances, setback lines checked against both state and local requirements, parking layout, utility connection schematic, owner-occupancy notation where required. PDF in [insert turnaround].
Garage Conversion ADU Site Plan — $159 Existing garage footprint, classification change notation, exterior entrance and egress window locations, fire separation notes where applicable.
Junior ADU (JADU) Site Plan — $119 Primary dwelling footprint with JADU location indicated, exterior entrance shown, utility separation notes. Lighter scope than a detached or garage conversion plan.
Attached Addition ADU Site Plan — $259 Addition footprint integrated with existing house, primary dwelling setback framework, entrance location, parking layout.
What to Send When You Order
- Property address and state
- ADU type: detached new construction, garage conversion, JADU, or attached addition
- Approximate ADU size and proposed location
- Whether the property is on municipal sewer or private septic
- Your municipality’s ADU permit checklist if you have it
- Whether you’re aware of any applicable state preemption rules — if you’re not sure, send the address and we’ll check
Frequently Asked Questions
A: At minimum: the primary dwelling footprint, proposed ADU footprint or location, separation distance between them, setback lines per the applicable standard (state or local, whichever governs), parking layout where required, utility connection routing, and any owner-occupancy or designation notations required by the jurisdiction.
A: An addition is an extension of the primary dwelling. An ADU creates a separate, self-contained dwelling unit on the same lot. The site plan for an ADU has to show elements specific to a second dwelling — separation distances, parking for the additional unit, utility connections for an independent unit — that a standard addition plan doesn’t require.
A: Depends on your state and the specific ADU configuration. California, Oregon, and several other states have imposed maximum setback limits that override more restrictive local rules for most ADU types. Texas limits HOA authority but doesn’t preempt local zoning setbacks directly. The answer is jurisdiction and ADU-type specific — we check before drawing.
A: Depends on your jurisdiction and whether state law has eliminated the requirement. California has eliminated ADU parking requirements in most circumstances. Many other states still require one off-street space per ADU. Some jurisdictions exempt properties within a specified distance of public transit. We check the current requirement for your jurisdiction before drawing the parking layout.
A: In many jurisdictions with ADU-enabling legislation, yes — states that have loosened parking requirements often also eliminate the replacement parking requirement for garage conversions specifically. In jurisdictions that still require ADU parking, converting a garage to a JADU or ADU may require providing replacement parking elsewhere on the lot. This is one of the first things we check when a garage conversion order comes in.
A: It depends on the jurisdiction and the utility provider. Some require separate meters for independently rentable ADUs. Others allow shared service with a submeter arrangement. Some require separate meters only above a certain ADU size threshold. The site plan typically shows the connection routing — the metering decision is confirmed with your utility provider.
A: For zoning review purposes in most jurisdictions, no. A non-certified scaled drawing is what the planning or building department accepts for the site plan portion of an ADU application. Structural, electrical, and plumbing drawings may require licensed professional involvement — those are separate documents from the site plan.
A: A permitted ADU adds assessed value to the property. The amount varies by jurisdiction and by how the assessor values the new unit. This is worth knowing before applying but is outside the scope of a site plan — a local real estate attorney or CPA can give you a jurisdiction-specific answer.