Home Addition Cost Per Square Foot (2026)

A home addition costs $150 to $400 per square foot in 2026, with most projects between $200 and $300. A small bump-out is at the low end; a second-story addition or one containing a kitchen or bathroom is at the high end.

Cost breakdown

• Bump-out (a few feet, cantilevered or small footing): $150-$250 per sq ft.
• Standard ground-floor room addition (new foundation, roof tie-in): $200-$320 per sq ft.
• Addition with a bathroom or kitchen: $300-$450 per sq ft.
• Second-story addition: $300-$500 per sq ft (structural reinforcement, temporary roof, whole-house disruption).
• Sunroom / three-season room: $100-$300 per sq ft depending on whether it's conditioned.
• Design, engineering, and permits: $3,000-$15,000+.

What actually drives the price

Addition type is the biggest driver: a bump-out reuses much of the existing structure, a full addition needs its own foundation and roof, and a second story needs the existing structure reinforced and the house opened up. Then: plumbing and electrical scope, foundation type and soil, roof tie-in complexity, matching existing siding and windows, finish level, and local permitting and impact fees.

Match the plan to the foundation question

The number hinges on what's under and over the new space. Photos of the area, the existing foundation and roofline, and the yard grade — plus whether the addition needs plumbing — let you give a per-square-foot range. Firm pricing needs plans, engineering, and a site visit.

Scoping this job from photos

The visible factors — size, access, condition, and finish level — are usually enough for a first-pass range from a few photos and a short description of what the customer wants. A final walkthrough is still worth doing before a firm number, since what's behind walls, underground, or under a surface can't be seen in a photo. Fast Snap Pro lets a customer send photos and describe the job so you can return a realistic starting range before scheduling the on-site visit. See also the bathroom remodel cost guide and kitchen remodel cost guide.

Frequently asked questions

How much does a home addition cost per square foot in 2026?

$150 to $400, most commonly $200 to $300. Additions with a kitchen or bathroom, and second-story additions, run higher.

Why is a second-story addition so expensive?

The existing structure has to be reinforced to carry the load, the roof comes off temporarily, and the whole house is disrupted — often $300 to $500 per square foot.

What's the cheapest type of addition?

A bump-out of a few feet, which can sometimes be cantilevered off the existing structure and avoid a full new foundation.

Can an addition be quoted from photos?

Only a rough per-square-foot range; a real quote needs architectural plans, structural engineering, and a site visit for foundation and grade.

Give faster ballpark numbers

Try Fast Snap Pro to turn customer photos into a starting price range built on your own rates, before you schedule the in-person walkthrough.