How Much Will Your Home Addition Really Cost?
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What type of addition are you planning?
Select the option that best matches your project.
Average Costs by Addition Type
National 2026 averages. Your cost will vary based on location, size, and finish quality.
Bedroom Addition
$20K – $75K
avg $42,500
Bathroom Addition
$25K – $90K
avg $54,000
Sunroom
$15K – $80K
avg $38,000
Garage Addition
$23K – $65K
avg $38,500
Second Story
$100K – $300K
avg $175,000
Kitchen Extension
$30K – $120K
avg $65,000
How Our Calculator Works
Unlike generic online calculators that spit out a single national average, we factor in three variables that actually move the number: addition type, your local labor market, and finish quality. Here's the exact process.
Tell us about your project
Pick your addition type, square footage, and finish quality. Each variable feeds directly into our cost model — no vague approximations.
We adjust for your location
Your ZIP code maps to one of seven US cost regions. Labor markets in San Francisco run 35% above the national average. Rural Texas runs 12% below. Your estimate reflects that.
We apply real construction data
Our base costs come from RS Means Building Construction Cost Data and NAHB survey data, calibrated against 2026 Bureau of Labor Statistics Producer Price Index figures.
You get a full breakdown
Not just a number. You get a cost range, per-category breakdown, timeline estimate, and ROI projection — everything you need to walk into a contractor meeting prepared.
Our formula: Base cost = Square footage × Base cost per sq ft (by type). Then we apply a regional multiplier (0.88 to 1.35), a quality multiplier (0.70 to 2.00), and add any selected features. The result is shown as a range — low at 85% of midpoint, high at 120% — because no two projects are identical. Read the full methodology.
What Drives Your Final Cost
Five factors account for 90% of the variance in home addition costs. Understanding them helps you control what you can and plan for what you can't.
This breakdown is specific to our calculator's methodology. For in-depth analysis of each factor, see our 2026 cost guide.
Labor is the biggest variable in any addition project, and it moves dramatically by region. A framer in New York City earns roughly 2.4x what the same framer earns in rural Mississippi. Skilled trades — plumbers, electricians, HVAC techs — are in short supply in most metros, which pushes rates higher. For a 300 sq ft bedroom addition, labor alone often runs $15,000 to $28,000 depending on where you build.
Lumber, concrete, drywall, and roofing materials are commodity-priced and shift with supply chains. Lumber prices swung 400% between 2020 and 2023. Our data is calibrated to 2026 Bureau of Labor Statistics Producer Price Index figures, which we update quarterly. Finish materials (flooring, cabinetry, fixtures) have the widest range — you can spend $2,000 or $20,000 on flooring for the same 300 sq ft room.
Most homeowners forget about permits until they're deep in contractor quotes. Building permits alone run $1,500 to $5,000 for a typical addition, depending on your municipality. If you need architectural drawings (required for structural changes, second-story additions, and most additions over 200 sq ft), add another $3,500 to $8,000. Our calculator includes a permit line item when you select it as a feature.
Foundation costs are the hardest to predict before a site assessment. A simple slab for a ground-floor addition might cost $6,000. Reinforcing an existing foundation to support a second story can run $20,000 to $50,000. If your soil has drainage issues or you're building in a frost-prone climate, those costs climb further. Always budget a 15–20% contingency for foundation surprises.
A sunroom costs far less per square foot than a bathroom, because bathrooms require plumbing rough-in, waterproofing, and expensive tile work. A second story costs more than a ground-floor addition because it requires structural engineering, a staircase, and usually a temporary relocation during construction. Our calculator adjusts the base cost per square foot for each addition type, so these differences are already baked into your estimate.
Construction Costs by Region
Where you build matters as much as what you build. Click or tap a region to see how local costs compare to the national average of $107/sq ft.
Click a region
Select any region on the map to see average costs, regional multiplier, and market context.
From the Blog
View all →Bedroom Addition Cost: Complete Pricing Breakdown
A bedroom addition costs $20,000 to $75,000 in 2026. Full breakdown by size, quality tier, and region. Includes master suite and walk-in closet costs.
How Much Does a Home Addition Cost in 2026?
National average home addition cost ranges from $20,800 to $73,500, with a median of $46,000. Here is the full breakdown by type, size, and region.
Home Addition ROI: Which Additions Add the Most Value?
Most home additions recoup 50-70% of their cost at resale. Here is an honest breakdown of ROI by type, plus when the financial case actually makes sense.
Frequently Asked Questions
Real questions from homeowners planning additions.
Our estimates are within 20–30% of actual contractor quotes for most projects. That's intentional — we show a range, not a false-precision single number. The range tightens when you provide your ZIP code, because regional labor costs are the biggest variable. Treat the midpoint as your planning number, then get three contractor quotes to sharpen it. Our data is sourced from RS Means and NAHB surveys and updated quarterly.
The estimate covers hard construction costs: foundation, framing, roofing, mechanical systems, and interior finishes. It doesn't include: temporary housing during construction (common for second-story additions), landscaping to repair excavation damage, furniture and decor, moving costs if you're relocating during the build, or HOA approval fees. Add 10–15% to your budget for these soft costs.
We update our base costs, regional multipliers, and feature costs every quarter — January, April, July, and October. Each update pulls from the Bureau of Labor Statistics Producer Price Index and cross-references against the RS Means annual cost data. The update date is shown in the footer and in our methodology page.
Yes, always. Our calculator gives you a planning number. The real number comes from licensed contractors who walk your site, assess your existing structure, and factor in local permit requirements. Three quotes is the minimum — we've seen bids on the same project vary by 40%. Our estimate helps you spot outliers (too high or suspiciously low) before you sign anything.
Only if you select "Permit costs included" in Step 5 (Additional Features). We separated it because some homeowners pull permits themselves, some roll them into contractor contracts, and some (incorrectly) skip them. Our permit estimate covers typical building, electrical, and mechanical permits — not legal or zoning variances, which vary widely and require a local attorney or permit expediter.
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