WALLSECTION draws a complete exterior wall section in one command: strip footing, foundation wall, basement slab, sill plate, floor framing, stud wall with plates and finishes, and the eave with rafter, fascia and soffit — with concrete hatching and batt insulation. It is the drawing every set of house plans needs and nobody enjoys redrawing.
What WallSection does
Every dimension is a parameter, and the section is built rather than plotted. Each part is a function that knows where the part below it finished, so changing the joist depth moves the wall, the eave and the insulation up with it.
That is the difference from a section drawn from hard-coded points. A routine with the gypsum at 0.5, the sheathing at 0.625, the plates at 2 and the roof fixed at 30 degrees draws exactly one house — change the pitch, use 2×4 walls, or work somewhere that does not build at 30 degrees, and it is no use.
How to use it
- Load the routine with
APPLOAD, or put it on your support file search path. - Type
WALLSECTION. - Give the wall build-up, framing sizes, foundation dimensions and the roof pitch as rise and run.
- Pick one point: the inside face of the finished wall, at floor level.
How it works
You pick one point — the inside face of the finished wall at floor level. That is the point a builder dimensions from and the one an architect draws the room to.
From there the section builds outward and downward:
x = 0 inside face of the plasterboard
x = -gypsum face of the studs
x = -gypsum-stud back of the studs
x = -gypsum-stud-sheathing outside face, foundation below
y = 0 top of the subfloor
downward joists, sill plate, foundation, footing
upward plates, studs, top plates, eave
The section is drawn with the outside to the left, which is the convention for a wall section read alongside a plan with north up.
The eave. The rafter bears on the outside top corner of the wall, slopes up at the pitch you give as rise and run, and is cut plumb at the tail — which is what a rafter tail actually is, and why the fascia stands vertical.
A rafter of perpendicular depth D cut plumb measures D / cos(pitch) on that vertical cut. That one relation places the whole tail.
Notes and limits
- One pick point, at the inside face of the finished wall at floor level.
- Outside to the left, by convention.
- Every dimension is a parameter — no magic numbers in the geometry.
- One undo group covers the section.
Download and details
| Name | WallSection — draw an exterior wall section from footing to eave |
| Download | WallSection.lsp — 22.1 KB, plain AutoLISP source. Downloads directly; no zip to unpack. |
| Type | AutoCAD AutoLISP routine |
| Command | WALLSECTION |
| Requires | nothing beyond a CAD platform with AutoLISP. |
| Source size | 22.1 KB, 504 lines |
| Error handling | Yes — a *error* handler restores every system variable it changed, on cancel as well as on error. |
| Undo | The whole operation is wrapped in a single undo group, so one U reverses all of it. |
| Compatibility | AutoCAD (any release with AutoLISP), BricsCAD, ZWCAD, GstarCAD, ProgeCAD and other IntelliCAD-based platforms. AutoCAD LT needs a LISP enabler. No .NET, no ObjectARX, no installer. |
| Author | YZ, August 2026 |
| Licence | Free to use, supplied “as is” with no warranty. |
References
- WALLSECT LISP — a 1994 student take on the same drawing
- BATT LISP — the insulation symbol on its own
- FLOORJOIST LISP — the framing in plan
- More free AutoLISP routines on this site
- Wisey’s Steel Shapes — free structural steel section drawing program