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HomeServicesDetached ADU

Common project type

Detached ADU

A detached ADU creates a separate home on the same property. The first design decision is where it can sit while leaving a workable route for residents, construction and utilities. A catalog footprint is a starting point for that discussion, not proof that a building fits.

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Before a proposal

Three things must become clear.

  1. 01Is this the right project type?
  2. 02What does this property require?
  3. 03What is included in writing?

A service page is an orientation tool—not a permit decision, survey, construction document, final price, or guaranteed schedule.

Plan the space between the homes

Compare entrances, outdoor areas and window positions with the primary residence. A layout that looks comfortable in isolation can interrupt circulation or leave little privacy once placed on the lot.

  • Where will residents enter without crossing a private patio?
  • Which existing trees, paths and structures need to be documented?
  • How will daylight and windows relate to the main home?

Connect a separate building to the site

A freestanding home introduces its own foundation and utility routes. Ask the project team to separate building work from trenching, drainage, site restoration and access work so those items do not disappear inside a model allowance.

  • What survey and soil information is needed for foundation design?
  • Can crews and materials reach the proposed location?
  • Which utility connections and capacity checks belong in the scope?

Adapt the steel-frame concept before fabrication

Coordinate openings, insulation, exterior enclosure and service penetrations with structural design. Final dimensions and connection details must follow project documents and agency review before the frame is ordered.

  • Who coordinates structural and enclosure details?
  • Which property constraints could change the footprint?
  • What is included in permitting, inspections and handoff?

Questions before choosing this scope

Can I choose a model before checking the property?

Yes, as a comparison exercise. Test its footprint in the property tool, then verify boundaries, access, utilities and the applicable agency path. A fit preview is not a survey or an approval.

Is detached construction always cheaper than an addition?

No project-specific comparison is available without both scopes. Separate the building, site work, utility work and changes to the existing home before comparing written proposals.

Resources for the next decision

These are planning resources, not a finding about your property. Confirm current requirements with the responsible agency.

  • California HCD ADU resources and handbook
  • Build a preliminary cost scenario
  • How cold-formed steel framing is coordinated
  • Compare the Studio 400 detached concept
  • Compare the Courtyard 850 detached concept

San Jose local permitting

Planning this ADU scope in San Jose?

The San Jose flagship guide covers the 2026 Universal Checklist, City-versus-State development standards, SJPermits/SJePlans, fire-flow letters, preapproved plans, cost ranges, and property qualification.

San Jose ADU requirements

The useful next decision

Confirm the property before committing to detached adu.

A preliminary property review can identify available records, missing information, map corrections, and an early fit direction. Professional review still controls final design and approvals.

Have a specific property or question?

Share the address and intended use so the conversation starts with the correct context.

Compare another direction

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Attached ADU

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ADU Design and Permitting

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Local planning guides

Explore planning questions by city. These guides do not confirm service availability or property eligibility. Check current records and agency requirements for the actual address.

  • Los Angeles
  • San Jose
  • San Francisco
  • San Diego
  • Oakland
  • Berkeley
  • Palo Alto
  • Mountain View
  • Sunnyvale
  • Cupertino
  • Santa Monica
  • Pasadena
  • Irvine
  • Santa Clara
  • Fremont
  • Hayward
  • Long Beach
  • Anaheim
  • Sacramento
  • Fresno

Let’s build your ADU

Your property.
Your next chapter.

Explore the possibilities for your California property.

Check my property
Architectural concept of a modern California ADU in a landscaped garden, shown in natural daylight
Design concept

Let’s talk about your project.

(650) 400-7606sales@adu.zone

San Jose office

84 West Santa Clara Street Suite 700
San Jose, CA 95113
(650) 400-7606Get directions

Walnut Creek office

1990 N California Blvd, 8th Floor
Walnut Creek, CA 94596
(925) 744-5040Get directions
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