Home Additions in Alamo, CA
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Zoning Shapes Alamo Additions
Alamo is largely zoned for larger lots. In the common R-20 district, for example, the standards are a 20,000 sq ft minimum lot, a 25-foot front yard, side yards of at least 15 feet each and 35 feet combined, a 15-foot rear yard and a height limit of 2½ stories or 35 feet. Hillside agricultural parcels have larger minimums. An addition that does not fit the standards needs a variance, which the County Zoning Administrator decides, sometimes without a public hearing. The Alamo MAC may comment first.
The Alamo Municipal Advisory Council (MAC), formed in 2009, advises the County Board of Supervisors on land use and planning. Its Land Use Planning Subcommittee reviews County applications in Alamo and makes recommendations to the District Supervisor. The MAC is advisory and does not approve projects. It meets the first Tuesday of each month at 6 p.m. at the Alamo Women’s Club, 1401 Danville Boulevard.
Addition Work
County Tree and Creek Rules
- Protected trees (County Code Ch. 816-6): listed native species, including coast live, valley and blue oaks, measuring 20 inches or more in circumference at 4½ feet, are protected in riparian areas, oak woodland or savanna, or in stands of four or more. A permit is needed to remove one or to trench, grade or fill inside its dripline, applied for at least 10 days ahead. Dripline fencing is required during construction.
- Creeks: 30 to 50 feet from the top of bank along unimproved channels, verified before the building permit.
Permits and Inspections
Department of Conservation and Development, Application and Permit Center
30 Muir Road, Martinez, CA 94553 · (925) 655-2700
Monday to Thursday 7:30 a.m. to 5 p.m., Friday 7:30 a.m. to 4 p.m. Applications are filed online through the County ePermits Center; plan review is fully electronic.
County inspections: request through ePermits or the automated line at (925) 646-4108. Phone requests for same-day inspections are accepted until 5:30 a.m., Monday through Friday. The permit and stamped plans must be on site, with an adult present.
Fire sprinklers: under County building rules, an addition to a home without sprinklers does not trigger them unless at least 50% of the wall length and 50% of the roof are removed or replaced within a year. The San Ramon Valley Fire Protection District serves Alamo and reviews plans where required.
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Alamo Home Additions FAQ
Who approves additions in Alamo?
Contra Costa County. The Alamo MAC may review and comment, but decisions are made by the County.
What if my addition does not meet setbacks?
A variance is decided by the County Zoning Administrator.
Are oak trees protected in Alamo?
Yes, under the County tree ordinance in qualifying settings, including work inside the dripline.
Does an addition require fire sprinklers?
Not under County rules, unless at least half the walls and half the roof are replaced within a year.