Room addition cost in Sacramento & the Bay Area
Contractors declared a value on 1,592 room addition permits in 2025–26 in the cities we track (Sacramento, Elk Grove, West Sacramento, San Francisco, San Jose, Marin County). Half of the jobs fall between $49,712 and $250,000; the median is $107,354. A declared value is what the contractor reported to the city, so your quote can be higher or lower, and prices differ from city to city.
$49,712Low (25%)
$107,354Median
$250,000High (75%)
1,592Permits