HOUSESHELL builds the outside of a simple house as 3D faces: floor, four walls, the eave soffits, the fascia, and a roof that is either gabled or hipped.
What HouseShell does
It is a massing model, not a set of construction drawings — the thing you want for a site study, a shadow test, a streetscape, or a quick view to show a client the shape of a proposal.
Each part goes on its own layer, so the roof can be recoloured, the walls hidden, or a street of them varied without touching the geometry.
Gable runs the ridge the full length, out to the overhang, with the end walls carrying straight up to it as triangles. Hip stops the ridge short at each end by a setback you give, and the roof falls away in four directions instead of two.
How to use it
- Load the routine with
APPLOAD, or put it on your support file search path. - Type
HOUSESHELL. - Pick the corner and give the plan dimensions, wall height, roof rise and overhang.
- Choose Gable or Hip. For a hip, give the ridge setback.
- Use
FACEHOLEafterwards to cut window and door openings.
How it works
The raked eave. On a gable the eave overhang at the ends is not level — it climbs with the roof. Its rise is the overhang measured up the slope:
slope angle = atan(rise ÷ half-span)
eave rise = overhang × tan(slope angle)
Which is the same number you get going the long way round through the hypotenuse, stated directly.
The question is asked as what it is. “Is the roof vertical on the ends?” is a question about the answer rather than about the roof. Gable or Hip is what a drafter is actually deciding.
Notes and limits
- It is a shell, not a building. No openings, no internal structure — use
FACEHOLEfor windows and doors. - Each part is on its own layer, so a street of them can be varied by layer rather than by editing.
- A hip needs a ridge setback. Setting it to zero gives you a pyramid.
- One undo group covers the whole shell.
Download and details
| Name | HouseShell — build a 3D house shell, gabled or hipped |
| Download | HouseShell.lsp — 13.3 KB, plain AutoLISP source. Downloads directly; no zip to unpack. |
| Type | AutoCAD AutoLISP routine |
| Command | HOUSESHELL |
| Requires | nothing beyond a CAD platform with AutoLISP. |
| Source size | 13.3 KB, 307 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
- FACEHOLE LISP — cut window and door openings through the walls
- FLRJOIST LISP — framing members in 3D
- ROOFPITCH LISP — working with roof slopes
- More free AutoLISP routines on this site
- Wisey’s Steel Shapes — free structural steel section drawing program