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HomeServicesHome Addition

Common project type

Home Addition

A home addition expands the primary residence. Begin by deciding whether the goal is more space for one household or a separate living unit. That distinction shapes the design brief and the approval questions; an addition should not be marketed as an ADU by default.

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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.

Improve the whole floor plan

Consider how new rooms connect to existing circulation, daylight and outdoor space. An extension may need changes inside the original home to work well, so include those changes when comparing options.

  • Which daily problem does the extra space solve?
  • Will existing rooms lose windows or useful circulation?
  • Would reworking the current layout address part of the need?

Resolve the structural and enclosure junction

Document the existing foundation, framing and roof where the addition connects. Ask the required professionals to define how loads, movement, drainage and weather protection will be addressed.

  • What existing drawings and investigations are available?
  • Where do new and existing roofs discharge water?
  • Which system upgrades extend beyond the addition itself?

Plan work around the household

Discuss occupied areas, construction access, temporary facilities and service interruptions. Include restoration and a decision process for concealed conditions in the written scope.

  • Which rooms become unavailable and during which work?
  • How will construction be separated from residents?
  • What work is excluded from the addition proposal?

Questions before choosing this scope

Is an addition subject to the same path as an ADU?

Do not assume the paths are interchangeable. Confirm whether the proposal expands the primary dwelling or creates a separate unit, then ask the jurisdiction about the applicable review.

Can I compare a home addition with an attached ADU?

Yes. Compare the intended household arrangement, entrances, internal connections and required systems. Have the design team define each scope before comparing price or construction disruption.

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 home addition.

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

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Service direction

Attached ADU

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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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