Home additions — San Mateo, CA

Last updated: September 24, 2026

What affects the price

When you plan a total home transformation, the final number depends on several moving parts. The biggest factors are the square footage involved, the current condition of your home’s systems, and the level of finishes you choose. Opting for high-end materials like custom cabinetry or premium stone countertops will push your budget higher than standard selections. Structural changes, like moving walls or updating outdated electrical and plumbing, also impact the overall investment. We can provide you with exact pricing confirmed free on the call.

About this service

Adding square footage involves building outward or upward to create more living space. This is the right move if your family is growing or you need a dedicated office or extra bedroom without moving. Because you are essentially building a new structure attached to your house, site preparation and foundation work are required. Costs vary based on the size and complexity of the new build, and exact pricing is confirmed free on the call.

Frequently asked in San Mateo

Also serving nearby: Hayward · Daly City · Oakland · Sunnyvale · Fremont

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More on this: DOE Energy Saver — whole-home efficiency planning.

Service area details

Serving all of San Mateo — population 101,327; about 8,350 residents per square mile across 12.1 sq mi. ZIP codes covered include 94401, 94402, 94403, 94404, 94497.

Neighborhoods served in San Mateo: Downtown San Mateo, Bay Meadows, Shoreview, Aragon, Los Prados, San Mateo Park — and every surrounding area.