Cost guide
Home addition cost in Los Angeles.
Home additions in the LA area typically run $200 to $700 or more per square foot — priced per foot rather than as a flat number, since the total scales directly with how much space you’re adding.
Three rough tiers
A new room (or rooms) added at ground level. For an 800 sq ft addition, roughly $160,000–$280,000 before design and permits.
Structural reinforcement of the floor below, a new staircase, and roof removal all add cost beyond a single-story addition. For 800 sq ft, roughly $200,000–$400,000.
Premium finishes, a difficult site, or significant structural work. A kitchen or bathroom included in the addition also pushes toward this tier.
What actually moves the price
- Single story vs. second story. Building up means reinforcing what’s below, adding a staircase, and dealing with an existing roofline — all real cost beyond just the new square footage.
- What’s in the addition. A bedroom or family room is far cheaper per foot than a kitchen or bathroom, which need their own plumbing and ventilation.
- How it connects to the existing house. Matching rooflines, siding, and foundations to an older home often costs more than the new construction itself.
- Soft costs. Design, structural engineering, and permitting are commonly left out of a bare per-square-foot number — budget 10-20% of the construction cost on top for these.
- Site access. A tight lot that makes it hard to get materials and equipment to the build site adds labor cost that a simple, open lot doesn’t.
Why the range matters more than one number
Per-square-foot pricing hides a lot — a 400 sq ft bedroom addition and a 400 sq ft kitchen-and-bath addition can differ by well over $100,000, even at the same per-foot rate for “basic” construction. The real number depends on what’s actually in the addition and how it meets your existing house, which is exactly what a contractor needs to see to quote accurately.
Ranges synthesized from multiple 2026 cost guides; Los Angeles-specific per-square-foot data was limited and inconsistent across sources, so these figures lean on broader metro-area benchmarks. Treat this as a planning range, not a quote. Get itemized bids from licensed local contractors for a real number.
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