How big a room will your roof actually give you? Pick a roof style, pitch, and span — the cross-section redraws live and shows the usable space. Includes a floor offset for designs where the attic floor sits below the top plate (extra headroom for free).
Roof & Building
Stick framing can use the full attic footprint.
Used for room floor area.
Example: 10 ft walls with floor truss tops at 9 ft → offset 1 ft. The roof starts 1 ft above your attic floor — free headroom.
Habitable rooms typically require ~2.1 m (6'11") over part of the area — check local code.
Usable room (at your minimum ceiling height)
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Live Cross-Section
Orange zone = floor area with at least your chosen ceiling height. Drawn to scale.
Details
Measure
Value
Disclaimer: This tool shows geometric space only — it is not a structural design. Attic truss room sizes are set by the truss engineer; floor load ratings, stair access, egress, and ceiling height minimums are governed by your provincial building code. Confirm any habitable-space plan with your truss supplier, building department, and where required a licensed engineer. See our roof framing guide for the full pros and cons.
How this works
The tool models your roof profile above the attic floor: ceiling height at any point equals your floor offset plus the rise of the roof from the wall inward. The "usable room" is the strip of floor where the ceiling clears your chosen minimum height. For attic trusses, the room is additionally capped at about half the span (typical engineered room width) — the webs own the rest. The gambrel model uses the classic symmetric profile: lower and upper slopes each cover a quarter of the span per side.