Basement & Additions

High-intent per-square-foot budgeting: basement finishing and remodel, room and home addition cost per sq ft, sunroom, and a garage conversion / ADU budget. Additions are structural and MEP work — use licensed pros, pull a permit and confirm code.

Planning estimate: this is a planning estimate from the numbers you enter and standard reference quantities — not a bid or a contract. Get itemized written quotes from licensed contractors and confirm measurements before you commit.

Licensed pros & permits: Structural, electrical, plumbing and gas work must be done by licensed professionals and usually needs a building permit and inspection. Confirm scope, permits and code with your local building department before you start.

Basement Finishing CostEstimate the cost to finish a basement from your square footage and the price per square foot you enter, with the formula, a worked 800 sq ft example and FAQ.Basement Remodel CostEstimate a basement remodel from your own line items plus a bathroom, wet bar or egress add-on, then apply a contingency you pick. Formula and worked example.Room Addition CostEstimate a room addition cost per square foot from the footprint and the price per square foot you enter, plus line add-ons. Formula, worked example and FAQ.Sunroom CostEstimate a sunroom cost from the footprint and the price per square foot you enter for a 3-season or 4-season build. Formula, worked example and FAQ.Garage Conversion / ADUBudget a garage conversion or ADU from the floor area and the price per square foot you enter, plus kitchen/bath/HVAC add-ons and a contingency you pick.

Every Basement & Additions tool is calculated server-side — visible immediately — with its formula, a worked example and a reference table, and works on the prices you enter. Background reading is in the guides.