Additions are priced per square foot, but the direction matters more than the size. Building out needs a new foundation. Building up means reinforcing everything underneath before you start.
This is a planning estimate, not a quote and not a bid. The rates behind it come from Los Angeles County projects and published 2026 cost data, reviewed 2026-10-29. Real pricing needs a site visit, because the things that move a construction budget most are rarely visible from the street. America General Contractors, California contractor licence CSLB 1083262.
Questions about this estimate
How big an addition can I build?
That depends on your zone, lot size, setbacks and the city's floor-area limit. In the City of Los Angeles most single-family homes are capped at a percentage of the lot. We check your specific parcel before any design work, at no cost.
Is this cheaper than building an ADU?
Per square foot they are similar. The difference is what you get: an addition makes your house bigger, an ADU makes a second rentable home. If the goal is income, the ADU usually wins. If the goal is a bigger kitchen or another bedroom off the hallway, the addition does.
How long does an addition take?
Nine to fourteen months from first meeting to finished room: 6 to 12 weeks of drawings, 2 to 4 months of city review, and 4 to 7 months of construction. A second storey runs longer.
Will my property taxes go up?
The new square footage is assessed and added to what you already pay. The rest of the house keeps its existing Proposition 13 assessment.
Read more
For the full picture, see room additions and the los angeles remodeling cost guide.
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