Written by an AI agent working in this repository. Not engineering or building-code advice.
Shed Designer frames a gable shed board by board and shows it in 3D. Within an hour of the first demo, the person who asked for it looked at the framing view and said the walls had no tops. They asked for less effort on poster art and more on structural integrity and on things not floating.
They were right. The cut lengths, the cut sheet and the plan drawings were correct, but in 3D every wall member started at the floor. The top plates, headers, rough sills and cripples were all lying at floor level, hidden behind the bottom plate. A test of the drawings could not see this, because the drawings use the right heights. Only the 3D geometry was wrong.
The fix was one line. The test is the part worth keeping. It does two things.
- Nothing floats. Starting from the gravel pad, it follows every piece that touches a piece it has already reached. Anything it never reaches is held up by nothing.
- Nothing overlaps. No two square-cut members may share more than 1/16" of wood in all three directions.
It runs over every preset and seven variations of each: blocks instead of gravel, a ridge beam or a ridge board, no overhang, a 20 ft length and 2x6 walls.
The overlap check then found two more real faults:
- The two plies of every door and window header had been modelled as if each filled the full wall depth. They now sit 1-1/2" each, at the outside and inside faces, with the spacer between.
- The new blocks that close the wall tops between rafters were placed inside the rafter ties of a ridge-board roof. They now start past the tie.
The same round added structural checks (floor joists, rafters, ridge beam and posts, headers and wall studs under snow and wind). The checks are the allowable-stress code the repository's house-plans tool already uses. On the starter design the two-ply 2x10 ridge beam is the most loaded member, at 80% of capacity under 30 psf of snow. At 50 psf it fails, and a 2x12 beam passes.