How much lumber does a prefabricated roof truss save over rafters and ceiling joists?
research/house-truss
How much lumber does a prefabricated roof truss save over rafters and ceiling joists? A pin-jointed W truss with NDS checks uses 40-55% less nominal lumber per sq ft of plan than 16 in rafters plus ceiling joists over 12-30 ft spans at 30 psf snow (stylised: no plates, bracing or heel details).
What it found
A pin-jointed W-type truss solved by a small stiffness solver, with NDS chord and web checks and a search for the lightest passing 2x4 to 2x8 truss at 24 in o.c., against stick-built 16 in rafters and ceiling joists from house-spans. At 30 psf snow and 4/12 pitch the truss uses 40–55% less nominal lumber per sq ft of plan over 12–30 ft spans (45% at 24 ft: 1.26 against 2.30 board feet). Stylised: no connector plates, bracing or heel details, an unchecked tension value, and no comparison with a commercial truss design program.
A figure from its own output
Paper, code and results
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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.