Home addition contractors in San Mateo, CA
No contractors are listed for addition work in San Mateo 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 San Mateo first. Projects that can't be approved at the counter go to plan check: at least four sets of plans, a valuation-based fee and up to 20 working days.
Source: City of San Mateo, Building Division, Oct 18, 2026
Home addition contractors in San Mateo
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 San Mateo 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 San Mateo
Permits go through City of San Mateo Community Development Department, Building Division. Put in the contract who pulls the permit.
San Mateo reviews kitchen and bath remodels over the counter, in person or virtually through its Citizen Self Service (CSS) portal, if the design is conventional with no structural calculations or Fire review. Plans are still required, and anything that takes a plan checker over 30 minutes goes to full review.
Source: City of San Mateo, Community Development Department, checked Oct 18, 2026
Any second-story addition to a one-story house, a new two-story house, or more than 50 sq ft added to a second story needs Single Family Dwelling Design Review. You must hold a pre-application meeting with Planning and notify owners and tenants within 500 feet first.
Source: City of San Mateo Municipal Code 27.08.032, checked Oct 18, 2026
Inspections are booked on CSS and happen within 24 hours, in a 9 a.m. to noon or 12:30 to 5 p.m. slot. Requests made after 4:30 p.m. roll to the next business day.
Source: City of San Mateo, Building Division, checked Oct 18, 2026
Detached one-story sheds up to 120 sq ft, painting and similar finish work, and detached decks up to 200 sq ft and 30 inches high are exempt. Almost everything else, including repairs, needs a San Mateo building permit.
Source: City of San Mateo, Building Division, checked Oct 18, 2026
What a addition job costs
Too few addition permits in San Mateo 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 San Mateo
Other project types in San Mateo
How this list is built
We have no city permit file for San Mateo 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.