Home Addition Cost Calculator: what to expect
A home addition adds new square footage, so unlike a remodel you're paying for foundation, framing, roof, and systems from scratch. That's why additions cost more per square foot than almost any interior remodel.
Across the United States, a home addition cost averages $125,246 once mid-range materials, licensed labor, and standard permits are included. The figures below are a national baseline; pick your state or city to apply local labor rates, material delivery costs, and permit fees.
Cost summary
| Low estimate | $71,459 |
|---|---|
| Average estimate | $125,246 |
| High estimate | $230,988 |
| Cost per sqft | $179 - $577 |
| Timeline | 10-28 weeks |
Where the money goes
For a typical home addition cost, the average $125,246 estimate splits into roughly $49,968 of materials, $47,796 of labor, and $3,200 in permits.
| Material cost | $49,968 |
|---|---|
| Labor cost | $47,796 |
| Permit cost | $3,200 |
What a home addition cost includes
- Foundation or slab and new framing
- Roofing tie-in and exterior siding to match
- Electrical, HVAC extension, and any plumbing
- Insulation, drywall, flooring, and interior finishes
- Permits, structural engineering, and inspections
What drives the cost the most
- New foundation and roof tie-in make additions pricier per square foot than remodels.
- Whether the addition includes plumbing (bath/kitchen) sharply changes cost.
- Matching existing rooflines, siding, and grade adds labor.
- Extending HVAC and electrical service may force capacity upgrades.
Budget, standard, and high-end scopes
The $71,459–$230,988 range maps to three common levels of finish:
| Scope | Roughly | What it covers |
|---|---|---|
| Bump-out | $71,459 | Small cantilevered extension, no new foundation — the cheapest way to add space. |
| Single room | $125,246 | Slab or crawlspace addition with one finished room. |
| Multi-room / 2nd story | $230,988 | Major structural work, new systems, sometimes a new roof. |
How to save on a home addition cost
- Build up (second story) only if the foundation can carry it — otherwise build out.
- Keep new plumbing back-to-back with existing lines to limit runs.
- Match, don't perfectly replicate, historic exterior details to control cost.
How this estimate is calculated
We start from a base cost-per-sqft for home addition cost and adjust it for finish quality, labor complexity, waste, and equipment, then apply national baseline indices. The figures update with the cost data and reflect mid-range, licensed-contractor pricing, not a binding quote.