Room Additions
Add the bedroom, family room, or second story your house needs — built to match the existing home. CoGeneral handles construction. If you don't have plans yet, we'll connect you with a trusted local architect — then we take it from there and build it.
- Single-story and second-story additions
- Foundation and structural work coordinated with your engineer
- Seamless transition with existing finishes
- Permit and inspection management included
Our process
- 1Free on-site consultationWe visit, listen, and measure.
- 2Detailed proposalTransparent scope, timeline, and pricing.
- 3PermitsWe handle the city paperwork end-to-end.
- 4Build with weekly updatesPhotos, milestones, and a single project lead.
- 5Final walkthrough & warrantyWe don't leave until you love it.
Get a Free Estimate
We'll call within 1 business day.
Room Additions — Frequently Asked Questions
How much does a room addition cost in the Bay Area?+
Ground-floor additions typically run $400–$650 per square foot. A second-story addition runs $500–$800 per sq ft because of foundation reinforcement, stairs, and roof work. A 400 sq ft master suite addition usually lands between $180,000 and $280,000.
How long does a room addition take?+
Most single-room additions take 3–5 months of construction after permits are issued. Permits run 2–4 months in most Peninsula cities. Expect 6–9 months total from signed contract to move-back-in.
Do I need a permit for a room addition?+
Yes. Any addition that changes the home's footprint, roofline, or square footage requires a building permit, structural review, and Title 24 energy compliance. We handle all city paperwork and inspections.
Can I stay in my home during the addition?+
Usually yes. We seal off the construction zone, keep your kitchen and at least one bathroom operational, and schedule loud or dusty work during the day. For full second-story additions, most homeowners move out for 2–4 weeks during framing and roof tie-in.
Is a second-story addition possible on my house?+
Most Bay Area homes can support a second-story addition, but a structural engineer needs to verify the foundation and load path. Some 1940s–60s slab homes need foundation reinforcement. We bring an engineer to the first site visit when a second story is on the table.