Written by an AI agent working in this repository, from test runs on 2026-10-29.
T1-11 and LP panels come 4 ft wide, so every vertical joint between two sheets needs a stud behind it: each panel edge is nailed to half of that stud. Shed Designer lays its studs out from the building corner on 12", 16" or 24" centres, so the 4 ft marks normally land on a stud.
A door or window breaks that. Its rough opening replaces the layout studs it covers with king studs, jacks, a header and cripples, and those sit where the opening needs them, not on the 4 ft line. When a joint lands on or just beside an opening, one panel edge can end up over air.
The shed designer's fuzz test, which builds random sheds and checks every rule it knows, now requires the "siding joints on framing" check to pass too. In a sweep of 1,500 random designs, 70 failed it, about 5%. A typical case was a window ending 2-3/4" short of the 8 ft mark on an 8'6" gable wall: the king stud carried one panel edge, and the next stud began 1" past the joint, leaving a 3/4" gap.
The fix is what a framer would do: a nailer. For each 4 ft joint between the plates, outside the rough openings, the tool finds where either panel edge has no wood. It then adds a stud-size piece flush against the framing that is there, running from the member below to the member above. Where the gap is narrower than a 2x (that king stud 3/4" from an end stud), the nailer is ripped to fit, and the cut list says so. A nailer goes in only if it collides with nothing.
After the fix, 0 of 1,500 designs fail. No preset changes, and no published lumber total moves, because their joints already landed on studs. The nailers only appear where a joint was bare.
The same stricter test also caught a mistake of ours from earlier that night. Moving an inner rafter clear of the gable wall had left an 8 ft roof-sheathing joint with no rafter under it, in 35 of the 1,500 designs. Sheet joints now snap to the rafter before the 4 ft mark.
Shed Designer is not engineered or code-checked; check fastening against your siding maker's instructions and local code.