Home Addition Cost Estimator
Estimate home addition costs by square footage, finish quality, and region.
Breaks down construction, permits, design fees, and contingency for budget planning.
Home additions run $95 to $600+ per square foot depending on location and finishes. The per-square-foot rate covers framing, roofing, insulation, drywall, windows, electrical, plumbing stub-ins, and finishes. It does not include furniture or landscaping.
Quality tiers
Basic means contractor-grade finishes throughout: standard windows, vinyl flooring, builder-grade fixtures. This is the floor for getting a livable, code-compliant space.
Mid-range is where most residential projects land: solid wood or quality laminate cabinets, tile flooring, standard-spec windows, recessed lighting. The gap from basic is visible the moment you walk in.
High-end adds hardwood floors, custom cabinetry, upgraded windows, detailed trim work. Luxury is full custom: specialty tile, premium appliances if it is a kitchen addition, smart home integration.
The costs people forget
Design fees run 8-15% of construction cost. Skip a licensed architect and hire only a draftsperson if you want to save money, but for structural work (a second story, a cantilevered extension) you need a licensed engineer at minimum.
Permits vary by municipality. A straightforward addition in a rural county might cost $800; the same permit in a major city costs $3,000-5,000. The $5/sq ft estimate here is a rough national average.
The 12% contingency is not optional. On any project over $50,000, unexpected costs are the rule: a beam where none was expected, old electrical that needs upgrading, moisture damage behind existing walls. Budget for it before the project starts, not after.
Timeline
A 400 sq ft addition typically takes 4-6 months from permit approval to punch list. Permitting itself takes 4-12 weeks depending on the municipality — and it happens before any construction begins.