Cost to Bump-Out Addition in Seattle, WA

$12,800–$64,000 in Seattle

28% above the national average · 1.28x cost multiplier

In Seattle, a bump-out addition runs $12,800 to $64,000 on average — about 28% above what homeowners pay nationwide. The West Coast market's labor costs account for most of the gap, with material pricing and local permitting fees adding to the spread. Use the cost table below to compare budget, mid-range, and premium options side by side.

Cost Breakdown in Seattle

Line Item	Low	Mid	High
Cost per sq ft	$115	$205	$320
Materials	$5,120	$10,880	$23,040
Labor	$7,680	$14,080	$28,160
Permits	$1,536	$2,560	$3,840
Design	$1,024	$1,920	$3,840
Total	$15,360+28% vs. national avg	$29,440+28% vs. national avg	$58,880+28% vs. national avg

Budget

Small 60-80 sq ft bump-out, cantilevered over existing foundation, no foundation work needed, standard materials matching existing siding.

Mid-Range

100-150 sq ft bump-out with foundation piers or slab extension, mid-grade finishes, energy-efficient windows, basic electrical.

Premium

200+ sq ft bump-out with full concrete foundation, premium materials, custom windows, dedicated heating/cooling, high-end finishes.

Material Options

Material prices below are national averages; availability in Seattle may shift costs slightly.

Material	Cost/Unit	Pros	Cons	Best For
Cantilevered (No New Foundation)	$90-$130 per sq ft	Lowest cost option, no excavation or foundation work, fastest construction	Limited to 2-foot extension maximum in most cases, some structural limitations	Small bathroom, closet, or bay window expansions of 2-3 feet depthLowest cost option, no excavation or foundation work, fastest construction
Concrete Pier Foundation	$110-$160 per sq ft	Good for medium-sized bump-outs, minimal excavation, stable support	Not suitable for very large bump-outs, some areas require frost depth piers	Bump-outs of 3-6 feet depth in moderate climatesGood for medium-sized bump-outs, minimal excavation, stable support
Poured Concrete Slab	$130-$190 per sq ft	Solid, stable, can support any size addition, good for kitchen/dining expansions	Requires excavation and grading, longer construction timeline	Kitchen or family room bump-outs where a durable floor is neededSolid, stable, can support any size addition, good for kitchen/dining expansions
Full Perimeter Foundation	$160-$250 per sq ft	Most stable, allows crawl space access, supports heavy loads and large bump-outs	Most expensive, requires extensive excavation, longest construction timeline	Large bump-outs over 150 sq ft or in areas with challenging soil conditionsMost stable, allows crawl space access, supports heavy loads and large bump-outs

Other Projects in Seattle

Full Kitchen Remodel

Full Bathroom Remodel

Composite Deck Building

Back to national average for Bump-Out Addition

Seattle Estimate

Typical Range

$12,800–$64,000

vs. National Average

28% above national

Cost Multiplier

1.28x

Cost Per sq ft

$115–$320

Estimates apply Seattle's 1.28x regional cost multiplier to national averages. Actual bids vary by contractor, project scope, and timing.

See national average costs →