How the attic-conversion composer builds one materials list from a dozen calculators
The attic-conversion calculator is a composer: you enter the attic once and it feeds a dozen standalone calculators, then merges their outputs into one list where every line traces back to its source. An attic pulls in more trades than most rooms — knee-wall framing, a reinforced subfloor, insulation at the roofline, and stairs all stack onto the same footprint.
What this diagram shows
A flow diagram of what the attic-conversion calculator does. On the left, the attic is entered once — its finished floor area, the roof pitch, the scope (habitable room versus a full ADU), whether a bedroom is being added, and the climate zone. Those shared inputs feed twelve standalone calculators that each run independently: framing for the knee walls and rafters, the subfloor, insulation, spray foam, drywall, interior paint, flooring, trim, interior doors, an egress window, the stairs, and the HVAC load check. Their outputs merge into one materials list on the right where every line is tagged with the calculator that produced it, so nothing is double-counted and the sloped-ceiling area is only paid for once. The composer never re-implements any math — it calls the same calculators you can use on their own and reconciles the surfaces they share.
Attic Conversion Calculator
Live attic conversion cost — bonus room, habitable, or full ADU. Dormer, stair, joist sister, mini-split adders. IRC R305.1 & R310 callouts.
