Home addition contractors in Sonoma County, CA
No contractors are listed for addition work in Sonoma County yet. CSLB license data dated Oct 16, 2026.
Which license do you need?
B license required. An addition needs a B (General Building) contractor. A B-2 may not touch footings, foundations, load-bearing walls or roof structure, and every addition does.
Do you need a permit?
Check with Sonoma County first. In unincorporated Sonoma County, additions, extensive remodels and new buildings need construction plans filed through Permits Online, and every new building or addition needs a building site evaluation, valid for one year.
Source: Permit Sonoma (County of Sonoma), Oct 18, 2026
Home addition contractors in Sonoma County
No contractors listed here yet.
We list contractors here only when city permit records or the contractor show they do addition remodels. None so far. For a wider set of licensed builders, see the Sonoma County general contractor list and ask each for addition projects they've finished.
Payment doesn't change the order. Business build-out? See commercial GCs. Each card shows CSLB data from the file dated Oct 16, 2026. Verify live on CSLB.
Permits in Sonoma County
Permits go through Permit Sonoma, Building Division. Put in the contract who pulls the permit.
Permit Sonoma's goal for building plan check is 6 weeks from the date you pay fees; site reviews are usually done within a week of payment.
Source: Permit Sonoma (County of Sonoma), checked Oct 18, 2026
Since Jan 1, 2017, a permitted remodel or addition in a Fire Hazard Severity Zone or Wildland Interface Fire Area must meet the wildland-urban interface rules in the building and residential codes.
Source: Permit Sonoma, Fire Prevention, checked Oct 18, 2026
Every building permit that needs plans gets a septic review. If the project adds wastewater flow, for example new bedrooms, a Qualified Consultant has to evaluate the existing system's capacity and condition.
Source: Permit Sonoma (County of Sonoma), checked Oct 18, 2026
Homes rebuilt inside the fire burn zones go through the Resiliency Permit Center ((707) 565-1788), with faster processing and reduced permit fees. Impact fees don't apply when you rebuild at the same floor area.
Source: Permit Sonoma (County of Sonoma), checked Oct 18, 2026
What a addition job costs
Too few addition permits in Sonoma County declare a value for us to publish a range. For an estimate by size and finish level, use the home construction cost calculator.
Planning an accessory dwelling unit? That has its own site: Bay Area ADU Builders.
B or B-2: which license fits your job
Both classes can act as your prime contractor. A B-2 is limited to remodels of an existing wood-frame house. If your plan changes the structure, look for a B.
| Job | B General Building | B-2 Residential Remodeling |
|---|---|---|
| Kitchen or bath remodel in an existing house | Yes | Yes, when the contract covers 3 or more unrelated trades |
| Addition or new rooms | Yes | No |
| Moving or removing a load-bearing wall | Yes | No |
| New home | Yes | No |
| Commercial or tenant work | Yes | No |
Sources: CSLB, class B and class B-2, checked Oct 18, 2026. More in B vs B-2.
California rules for your contract
A down payment on a home improvement contract can't be more than $1,000 or 10% of the price, whichever is less. No progress payment can be more than the work done or materials delivered.
Source: California B&P Code 7159.5, checked Oct 18, 2026
Work under $1,000 in total (labor and materials) that needs no building permit doesn't require a license. The exemption doesn't apply if the person advertises as a contractor, has employees, or splits a job to stay under the limit.
Source: California B&P Code 7048, checked Oct 18, 2026
Every licensed contractor must keep a $25,000 contractor's bond on file with CSLB. That has been the amount since January 1, 2023.
Source: CSLB, bond requirements, checked Oct 18, 2026
A contractor with employees must carry workers' comp. Until 2028, a B contractor with no employees can legally file an exemption, so check which one yours did. From January 1, 2028, a workers' comp certificate is required for every license.
Source: CSLB, workers' compensation, checked Oct 18, 2026
Complaint history isn't in CSLB's free data files, so we don't show it. Check complaints on CSLB before you sign.
Home addition contractors near Sonoma County
Other project types in Sonoma County
How this list is built
We have no city permit file for Sonoma County yet, so a contractor is listed only if it confirmed addition work to us. A contractor is listed only with evidence for addition work: a permit record whose description matches, or a source the contractor gave us.
License class, status, dates, bond and workers' comp come from CSLB's public data files: Master file Oct 16, 2026, workers' comp file Oct 17, 2026, processed Oct 18, 2026. Each card links to that license's live CSLB record. Full method.