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Home addition
Home Additions & ADUs

Don't move.
Add what you need.

For most Marin homeowners, the right play isn't moving — it's adding. The neighborhood, the schools, the relationships are already where you want them. The house just needs another room. We design and build additions that feel like the home was always supposed to have them.

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Why most additions look added.

You can usually tell when an addition was built — different rooflines, slightly off siding, a transition that doesn't quite work. The original home and the new portion fight each other instead of belonging to each other. That's almost always a design problem, not a budget problem.

We've added rooms to homes built in every decade from the 1920s to last year. The trick is letting the original home set the rules and matching them — roof pitch, eave detail, window proportion, siding reveal, trim profile — so the addition reads as part of the original story rather than a chapter pasted in. The square footage gets noticed; the seamless transition is what makes the home feel right.

What we build.

Primary suite additions

Bedroom, bath, walk-in closet — designed as a sanctuary on its own wing.

Kitchen expansions

Bump-outs, breakfast nooks, full kitchen relocations to bring in light and flow.

Family / great rooms

Open-plan additions that connect indoor living to the backyard.

Second-story additions

Adding a level to a single-story home. Significant structural and architectural design work.

Detached ADUs

Standalone accessory dwelling units. 600-1,200 sq ft typical. For family, rental, or flexibility.

Garage conversions

Converting an attached or detached garage into a JADU, office, gym, or studio.

Bump-outs

Smaller (50-200 sq ft) extensions where you just need a little more in one specific spot.

Architectural matching

Roofline, eave detail, siding, trim, window proportion — matched to the original home, not the catalog.

Foundation & structural

New footings, structural connections to existing, seismic detailing — engineered and inspected.

Addition framing

Process: from feasibility to handoff.

  1. 01

    Discovery call

    What you need, why now, what you've already considered. We're honest if an addition isn't the right answer.

  2. 02

    Site & feasibility walk

    Lot conditions, setbacks, soil, existing structure, design-review district. We map the constraints before drawing.

  3. 03

    Concept design

    Working with your architect or ours, we test the design against what the home and lot actually allow.

  4. 04

    Detailed bid

    Line-item, with risk areas identified. Permitting timeline included.

  5. 05

    Permits & approvals

    Plan check, design review where applicable, structural calcs, neighbor notifications.

  6. 06

    Construction

    Foundation → framing → mechanicals → finish. Weekly client updates with photos.

  7. 07

    Punch list & warranty

    Owner walkthrough at every major phase. One-year workmanship warranty on everything we touch.

Additions FAQ.

What types of additions do you do? +
Primary suite additions, kitchen expansions, family room and great room additions, second-story additions, ADUs (Accessory Dwelling Units), garage conversions, and bump-outs. Whatever's adding usable square footage to the existing home, we handle it.
How long does an addition take? +
A small bump-out (under 200 sq ft): 3-4 months. A primary suite addition (300-600 sq ft): 5-8 months. A second-story addition: 8-14 months. Permitting in Marin can add 3-6 months on top — sometimes more for second-story or hillside lots.
What does a Marin home addition cost? +
Single-story addition with mid-range finish: $700-$1,000 per square foot. Second-story addition: $900-$1,400 per square foot (more structural work, more lift). Marin's lot conditions, soils, and permitting add cost on top of the per-foot number — we'll provide a line-item bid early so there are no surprises.
Do I need an architect? +
For most additions, yes. We work with architect partners we trust or with the architect you've already engaged. For very simple bump-outs, we can sometimes draw the plans in-house. The Marin design review process for many neighborhoods makes architect-quality drawings worth the investment regardless.
What about ADUs specifically? +
California ADU law has streamlined approval significantly — most jurisdictions in Marin can't deny a code-compliant ADU. We've built detached ADUs, garage conversions, and attached ADUs. Whether you want it for family, rental income, or future flexibility, we'll match the type to the site and the goal.

Additions & ADUs across the Bay Area.

Pick the location that matches your project. Each page covers local permitting, neighborhood notes, and how we work in your area.

Need more room?

First call is free. We'll be honest about whether an addition is the right answer.

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