Can I Build an ADU on My Property? The 2026 Zoning Checklist

The most common question homeowners ask is: can I actually build an ADU on my property? The answer depends on your city's zoning rules, your lot size, setback requirements, HOA restrictions, and several other factors. This step-by-step checklist will help you determine your ADU eligibility before you spend money on architects and permit applications.

Step 1: Check Your Zoning District

The first thing to verify is whether your property is in a zone that allows ADUs. Most cities allow ADUs in single-family residential zones (R-1, RS, SF). Some also allow them in multi-family zones. Check your city's zoning map or look up your parcel on the county assessor website. In states like California, Oregon, and Washington, ADUs are allowed by right in all residential zones — no special permit needed.

Step 2: Verify Lot Size Requirements

Many cities have minimum lot size requirements for ADUs. Common thresholds: 3,200 sq ft (Los Angeles), 2,500 sq ft (Portland), 5,000 sq ft (Denver). Some cities have eliminated minimum lot sizes for ADUs entirely. California prohibits cities from requiring lots larger than 4,800 sq ft for ADUs. Check your lot size on your property deed or county parcel map.

Step 3: Measure Your Setbacks

Setbacks determine how close to property lines you can build. Typical ADU setbacks: 4 ft from rear and side property lines (California standard), 3-10 ft depending on city. Measure the available space on your lot after accounting for setbacks. Garage conversions often get reduced setback requirements since the structure already exists.

Step 4: Check Maximum ADU Size

Every city limits ADU size, usually based on lot size or primary home size. Common formulas: 50% of primary home up to 1,200 sq ft (California), fixed caps like 800 sq ft or 1,000 sq ft, lot-size-based sliding scales. Internal and attached ADUs may have different size limits than detached units.

Step 5: Review HOA and CC&R Restrictions

Here is a catch many homeowners miss: your HOA may have restrictions on ADUs even if the city allows them. However, several states (California, Washington, Oregon) have passed laws preventing HOAs from blocking ADUs entirely. In California, CC&Rs that unreasonably restrict ADUs are void and unenforceable. Check your HOA governing documents and state law.

Step 6: Evaluate Utilities and Access

Your ADU needs water, sewer, electricity, and potentially gas connections. Verify: Is your sewer line large enough for a second unit? Does your electrical panel have capacity? Can you run a separate water meter? Utility upgrades typically add $5,000-$15,000 to your project budget. Also confirm that your ADU will have legal access from a public road.

Step 7: Assess Parking Requirements

Parking used to be the biggest barrier to ADU construction. Most cities are now eliminating parking requirements for ADUs — especially near transit. California requires no additional parking within a half-mile of transit. Portland, Seattle, and Minneapolis have eliminated ADU parking requirements entirely. Check your city's current parking rules, as they may have changed recently.

Step 8: Look Up Your City's ADU Rules

Every city has different ADU regulations. Use our city-by-city guide to look up the specific rules for your area, including maximum size, setbacks, permit fees, parking requirements, and whether ADUs are allowed by right or require a conditional use permit. We cover 50 cities across 14 states.