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How much does a residential addition cost in Sonoma County?

Typical residential addition in Sonoma County
≈ $65,900
low confidencefrom 74 filings
≈ $27,700median ≈ $65,900≈ $125,000
A reference range from comparable filed projects in public records — not a quote.
Honesty is the point. We show the full range and the sample size — a reference, never a single promised number.
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Residential addition projects filed in Sonoma County typically run about $65,900, with most between $27,700 and $125,000, based on 74 filings (Sonoma County public records, DataSF).

These are comparable filed projects in Sonoma County — a typical reference range, not a quote. Your project can land anywhere in the spread depending on scope, materials, and access.

Where the money goes

A typical share of a residential addition budget — an illustrative industry breakdown, not measured for this project.

What moves the price

Materials & finishes
The biggest swing — basic vs premium
Labor & crew
Local rates and how many trades are involved
Scope found on-site
Older homes surface surprises once walls open
Filing & timeline
Reviews and inspections add weeks, not just cost

Common questions

What's the typical range for a residential addition in Sonoma County?

Most residential addition projects in Sonoma County run $27,700 to $125,000, with a median around $65,900, based on 74 filings of comparable filed work (Sonoma County public records, DataSF).

How recent is this data?

These figures reflect comparable residential addition projects filed in Sonoma County public records (DataSF), compiled as of 2026-06-03. They refresh as new filings are published.

What affects the cost of a residential addition?

Scope, materials, finishes, the age and condition of the home, and site access. The spread above ($27,700–$125,000) reflects that range — your project can land anywhere in it.

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