Home addition contractors in Alameda County, CA
No contractors are listed for addition work in Alameda 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 Alameda County first. R-1 zoning, which covers most unincorporated homes, sets 20 ft front and rear setbacks, 5 ft side setbacks (up to 10 ft on wider lots), a 25 ft height limit and 2 stories.
Source: Alameda County Planning Department, Oct 18, 2026
Home addition contractors in Alameda 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 Alameda 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 Alameda County
Permits go through Alameda County Public Works Agency, Building Inspection Department. Put in the contract who pulls the permit.
The County building department permits only unincorporated communities: Ashland, Castlewood, Castro Valley, Cherryland, Fairview, Happy Valley, Hillcrest Knolls, San Lorenzo and Sunol. A home inside a city goes to that city.
Source: Alameda County Public Works Agency, Building Inspection, checked Oct 18, 2026
Applications, plan uploads, inspection requests and status checks all go through the Alameda County Permit Portal.
Source: Alameda County Public Works Agency, Building Inspection, checked Oct 18, 2026
To see a property's past building permits, request the file before 2 p.m. Wednesday; staff pull it in 5 to 10 business days, and stamped plans must be viewed in person.
Source: Alameda County Public Works Agency, Building Inspection, checked Oct 18, 2026
What a addition job costs
Too few addition permits in Alameda 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 Alameda County
Other project types in Alameda County
How this list is built
We have no city permit file for Alameda 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.