Cost to Bump-Out Addition in Boise, ID

$10,500–$52,500 in Boise

5% above the national average · 1.05x cost multiplier

Expect to pay $10,500–$52,500 for a bump-out addition in Boise, about 5% above the national benchmark. The Mountain West region's contractor market and material costs account for most of this difference. The detailed breakdown below shows how budget, mid-range, and premium projects compare at Boise prices.

Cost Breakdown in Boise

Line Item	Low	Mid	High
Cost per sq ft	$95	$168	$263
Materials	$4,200	$8,925	$18,900
Labor	$6,300	$11,550	$23,100
Permits	$1,260	$2,100	$3,150
Design	$840	$1,575	$3,150
Total	$12,600+5% vs. national avg	$24,150+5% vs. national avg	$48,300+5% 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 Boise 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 Boise

Composite Deck Building

Full Kitchen Remodel

Central AC Installation

Back to national average for Bump-Out Addition

Boise Estimate

Typical Range

$10,500–$52,500

vs. National Average

5% above national

Cost Multiplier

1.05x

Cost Per sq ft

$95–$263

Estimates apply Boise's 1.05x regional cost multiplier to national averages. Actual bids vary by contractor, project scope, and timing.

See national average costs →