What is the 2026 cost range for a single-story addition scope home addition in San Francisco?

$217,000-$496,000, with the median landing near $356,500. The range reflects finish tier and layout complexity within the single-story addition scope; the San Francisco labor multiplier of 1.55× vs national median is baked in.

How long does a single-story addition scope home addition take in San Francisco?

18-26 weeks of on-site construction for the single-story addition scope, plus 10-26 weeks of permit review in San Francisco if the scope requires a permit. Cosmetic-only refreshes often skip permits; anything touching plumbing, electrical, or structural does not.

What is the single biggest budget-overrun risk for this scope?

Matching old siding or brick — if the material is discontinued, the whole elevation has to be reclad. $8-20K unexpected if not scoped up front.

Home addition — Single-story addition Cost in San Francisco, 2026

Low

$217K

$217,000

Median

$357K

$356,500

High

$496K

$496,000

Scope timeline: 18-26 weeksSan Francisco permit window: 10-26 weeksUpdated 2026-04-24

Why single-story addition × San Francisco produces this band

A single-story addition scope for a home addition in San Francisco combines two price levers: scope and metro labor rates. Single-story additions extend the existing footprint at grade — new foundation section, roof tie-in, and framing that matches the existing structure. No structural work on the original house beyond the tie-in. Against the national median remodel labor rate, San Francisco runs 55% above the national median — so the single-story addition band comes in at the mid-range, then scales 55% above the national median on top of that. Permit timelines for residential work in San Francisco typically run 10-26 weeks, which is the window you plan your design and decision sequence against. This page gives you the actual 2026 San Francisco bands for this exact combination, plus the three cost drivers Baily asks about first when scoping the project live.

What drives cost for a single-story addition scope

·Foundation extension (slab or stem-wall to match existing)
·Roof tie-in flashing and structural connection
·Exterior siding match (often requires whole-elevation repaint)
·HVAC extension into the new zone

What makes San Francisco different

Labor — Bay Area CSLB-licensed contractor scarcity keeps labor rates the highest in California.
Labor — Union framing and electrical rates carry a 30-35% premium over national median.
Labor — Tech-sector remodel demand (Noe Valley, Pacific Heights, Sea Cliff) competes for premium-finish crews.
Material — Victorian + Edwardian heritage restoration uses specialty millwork and painters — significant premium.
Material — Title 24 energy code same as rest of CA — envelope + glazing premium.

San Francisco rules that affect this scope

SF DBI permit process is notably long (10-26 weeks typical; discretionary review on most kitchen/bath >$25K).
Section 317 (Residential Demolition) controls ADU and addition work — lot merger and demolition ratio tracked.
Historic Preservation Commission review for Articles 10 + 11 properties adds 8-16 weeks.
Soft-story retrofit ordinance (SF Ordinance 66-13) affects multi-family properties with tuck-under parking.

Scope your home addition with Baily.

Baily asks the eight questions that determine where your project lands inside the $217K-$496K band for San Francisco and hands the scoped brief to one licensed builder.

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Questions LA homeowners actually ask

$217,000-$496,000, with the median landing near $356,500. The range reflects finish tier and layout complexity within the single-story addition scope; the San Francisco labor multiplier of 1.55× vs national median is baked in.