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HomeServicesAttached ADU

Common project type

Attached ADU

An attached ADU connects a separate living unit to the primary home. The connection is the central design problem: changes to the roof, structure, circulation and utilities must work for both households. Compare this direction with an ordinary home addition before commissioning plans.

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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.

Understand the existing home first

Gather permitted drawings where available and document what is actually built. The proposed opening and shared wall can affect load paths, existing rooms and the weather enclosure.

  • What structural information exists for the connection?
  • Will the addition remove windows or change a room’s daylight?
  • How will roof drainage and waterproofing meet at the junction?

Design two households around one connection

Place the entrance, kitchen, bathroom and circulation around independent daily use. Discuss acoustic separation and privacy as design objectives. Do not assume a shared wall means a shared household or a particular utility-meter arrangement.

  • Can each household enter without passing through the other home?
  • Where are plumbing, ventilation and electrical routes practical?
  • Which separation and utility arrangements require agency confirmation?

Sequence construction around occupancy

Work at the connection may affect occupied rooms and existing systems. Define temporary protection, access, service interruptions and restoration in the construction scope.

  • Can the main home remain occupied during each stage?
  • Who coordinates temporary weather protection?
  • Does the proposal include repairs inside the existing home?

Questions before choosing this scope

Does an attached ADU always need separate utility meters?

Do not assume that from the project name. Confirm the applicable connection and metering requirements with the permitting authority and each utility provider for the actual scope.

Can a detached catalog model be attached unchanged?

The detached concepts are useful for comparing room sizes, but they are not attachment plans. The building connection, access, structure and enclosure need project-specific design.

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

The useful next decision

Confirm the property before committing to attached 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.

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Related services

View the complete directory

Service direction

Home Addition

View details

Service direction

Detached ADU

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Service direction

ADU Design and Permitting

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Local planning guides

These reviewed agency-resource guides do not confirm service availability. Confirm current rules, property records, and agency requirements for the actual address.

  • San Jose
  • San Francisco

Ready for a useful first answer?

Start with your property, then talk through the details.

Review a preliminary site fit or request a property-specific conversation with the ADU California team.

AADU.zoneSteel-framed backyard homes

Property review, design, engineering coordination, permitting, steel framing, and construction support for California homeowners.

Preliminary online results are planning guidance, not a permit decision or site survey.

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