US House Cost Breakdown Generator — Real Line Items, Not One ZIP-Code Number

Search 'cost to build a house' and nearly every result is the same shape: type in a ZIP code and square footage, get back one number, usually built off a regional cost index. That number can be a reasonable starting point, but it can't tell you what happens to your budget when you switch from a crawlspace to a slab, add a third storey, or pick a complex hip roof over a simple gable — because there are no real line items behind it to recalculate.

This generator builds an actual itemized cost breakdown instead, organized by CSI MasterFormat divisions the way US builders, lenders and subcontractors already read a bid — wall and floor framing in real board feet, roofing area adjusted for pitch and shape, drywall and paint off real interior-surface coverage, a foundation line that changes with slab, crawlspace or basement. Change any input and the quantities recalculate, the same way a manual takeoff would.

It also does something most single-number calculators skip entirely: cross-checks your priced categories against NAHB's own published national stage percentages (framing typically ~17% of cost, foundations ~11%, and so on) and flags a category that's badly out of line — a free, real sanity check you can't get from a tool that only ever shows you one number to begin with.