Site and Building Standards

An ADU can be allowed in principle and still fail to fit the parcel under its zoning rules. Setbacks, separation, height, floor area, lot coverage, privacy, trees, and design conditions determine where a unit can go and how large it can be. The controlling measurements depend on the authority, zone, dwelling form, project state, lot geometry, and applicable overlays.

Find the rule that matches the project

• How are ADU setbacks and separation measured? explains which boundaries and distances to record.
• What height, eaves, storey, and roof limits apply? separates zoning height from building-code requirements.
• How much floor area, footprint, or lot coverage is allowed? shows why a maximum size is not a guaranteed buildable envelope.
• What privacy, window, landscape, and exterior-design rules apply? covers local design controls and the separate checks they can trigger.
• Can an existing structure or narrow lot receive dimensional relief? distinguishes an express exception from discretionary relief.
• Can a preapproved ADU plan fit my property’s zoning envelope? shows how to check a plan against a measured parcel and separate plan review from site approval.

Local standards and exceptions

These examples answer narrower questions for named places or legal pathways. Their measurements apply only under the stated local rules and conditions; start with the property’s current zoning record before using a number.

• What dimensions apply to a Vancouver laneway house? covers site width, floor-area calculation, setbacks, separation, height, and coverage.
• What is Toronto’s R 736 garden-suite exception? explains the rules for the specifically named Parkmount Road and Mountjoy Avenue lands.
• Which current Toronto garden-suite dimensions apply to my project? covers the current Chapter 150.7 setback, height, separation, coverage, and transition branches.
• What are Edmonton’s Section 6.10 backyard-housing dimensions? compares the height, area, setback, and separation conditions.
• What dimensions apply to a New York City ADU? summarizes zoning size, access, yard, height, and building-separation limits.
• How do San Diego ADU conversion dimensions differ from new construction? follows the city’s guidance for area, setbacks, and height.
• What are Ontario’s provincial ARU coverage and separation standards? explains the qualifying configurations and municipal overrides.
• Which California ADU size and setback protections may apply? separates conversions, detached units, and multifamily cases under state law.
• How do Milwaukee ADU dimensions vary by form? compares internal, attached, and detached units using the city’s guidance.
• What dimensional standards apply to a Massachusetts protected-use ADU? explains the state gross-floor-area definition and limits on local dimensional standards.
• How large can an ADU be in Seattle? summarizes the city’s gross-floor-area limits and their exceptions.
• How much floor area can a Denver ADU have? explains the zone- and form-specific gross-floor-area entries in Denver Zoning Code Section 11.8.2.
• What size and siting rules apply to a Portland ADU? summarizes Portland’s ADU living-area cap and selected detached-unit standards.

More local standards and pathways

• How do Kitchener detached-ADU roof height and setbacks work together? covers by-law 85-1 roof datums, height-triggered setbacks, and its lane branch.
• What dimensions apply to a Chicago coach house? covers coach-house height, open space, and separation.
• How do Austin HOME rules measure a two- or three-unit site? covers rear-yard and gross-floor-area rules under CI2026-0002.
• What dimensions apply to a DC accessory apartment? covers the principal-house and accessory-building paths.
• What envelope does Minneapolis allow for a detached ADU? covers floor area separately from combined site footprint.
• How large can a detached ADU be in Atlanta’s Bonaventure-Somerset District? covers a named historic-district area formula.
• Which San Francisco ADU size and height path applies? covers state-law routes by form and bedroom count.
• Does Sacramento’s local or state ADU standard apply? covers the two rule-selection paths.
• Which San José ADU dimensional path applies: City or State standards? compares San José’s complete City and State standards paths.
• What size and siting rules apply to Santa Ana ADUs? covers local area, height, setback, separation, and conversion branches.
• How do Boulder’s attached and detached ADU limits differ? covers standard and qualifying size limits.
• What lot size and ADU area does Honolulu’s FAQ describe? covers stated area bands and a threshold the FAQ leaves open.
• How does Albuquerque’s casita fit within the yard? covers placement, combined yard area, and setbacks.
• What ADU dimensions apply in Boston’s Mattapan zoning area? covers attached and detached local paths.
• Can a Denver ADU be built on a carriage lot without a main use? covers the code’s cross-referenced carriage-lot condition.
• How does Mesa measure ADU size and setbacks? covers the habitable-area formula and yard rules.
• How do San Antonio ADU dimensions vary by form? covers attached and detached standards.
• How does Saint Paul classify ADU setbacks by building separation? covers the toolkit’s six-foot branch.
• What does St. Louis Ordinance 72036 allow in the A Single-Family District? covers selected area and spacing terms.
• What did Tempe’s 2025 ADU guide and zoning opinion say? covers dated City statements and later permit guidance.
• How do Nashville detached ADU size and height rules change by lot? covers area, eave, ridge, and setback measures.
• What size and height does Salem’s ADU guide describe? covers general and special-use paths.
• How large and tall can a detached Charlotte ADU be? covers the area formula and height-triggered setback.
• How does Phoenix calculate ADU size and lot coverage? covers formulas around a 10,000-square-foot threshold.
• What ADU size and flood-zone limits does Durham’s code set? covers area branches and a mapped-location check.
• How do Berkeley ADU limits change on hillside lots? covers area and height paths by site status.
• What size, height, and yard coverage does Salt Lake City’s handbook describe? covers height-related setback guidance.
• What does Oklahoma City Ordinance 27847 require for an ADU? covers selected area, lot-width, and existing-structure provisions.
• How do Tacoma housing type and existing-structure status affect ADU dimensions? covers new construction and a bounded conversion path.
• What ADU size rules did Madison’s 2025 ordinance change? covers unit area, building footprint, and height.
• How does Sunnyvale’s 800-square-foot threshold change ADU review? covers permit and site-standard paths.
• Which Covina ADU size and review path applies? covers the streamlined class and planning standards.
• How do Oregon’s medium- and large-city ADU model codes differ? covers model configurations without implying local adoption.

Measure before relying on a number

Start with the parcel and current zoning record. Identify the governing municipality or planning authority, base zone, lot lines, street or lane condition, dwelling type, and whether the project is new construction, an addition, or a conversion. Then use the current by-law text and definitions to record each value with its units, measurement datum, applicable wall or lot line, exceptions, and effective date. A city summary can orient the search, but it may not include every overlay, amendment, or site-specific exception.

Zoning dimensions do not establish fire separation, emergency access, structural safety, accessibility, energy compliance, utility capacity, or permit approval. Check those requirements with the responsible building, fire, utility, and planning authorities as appropriate. When property geometry, existing permits, or the controlling rule is uncertain, a survey and written authority confirmation may be needed before design decisions are made.