Draw the walls
Sketch the outline on the plot grid. Walls join themselves: junctions split at T and X, corners mitre, collinear runs merge into one.
Plan · Openings · Roofs · Storeys
Draw the plan.The house follows.
Sketch walls on your plot and the wall graph does the rest: T and X junctions split, corners mitre, collinear runs merge — and the rooms, the perimeter and every surface compute themselves from the plan. Cut real openings, fit a roof, stack a storey. This is the core loop of Builder.
From four lines to a house.
Cut the openings
Windows, exterior and interior doors, garage, passages — real CSG booleans, subtracted from the wall solid. Rectangle, circle or triangle.
Fit the roof
Gable, hip, flat or shed — auto-fitted to the exact perimeter of your plan. Gable ends and shed wedges infill with the siding you picked.
Stack the storeys
Add a level: storeys, foundation and floor slabs all follow the plan. Rooms recompute as you drag — areas update, walls re-classify.
"I dragged one wall and the junctions split, the corner mitred, the roof refitted and both rooms renamed their areas. Nobody measured anything."
— the wall graph, on every dragOpenings
Cut real holes, not stickers.
Every opening is a CSG boolean — the wall solid is genuinely cut, so the reveal, the jamb and the light through it are real. Windows, exterior doors with steel pull handles, interior doors, sectional garage doors with panel relief, and plain passages between rooms.
Three shapes
Rectangle for windows and doors, circle for round windows, triangle for modern-barn gables — the opening follows the roof, not a template.
Doors that open
Exterior doors carry steel pull handles; garage doors are sectional with panel relief. In walk mode, E opens the door in front of you.
Passages, not doors
Open the plan between kitchen and hall with a passage — an opening with no leaf, the way Polish plans actually work.
Feature · Draw the plan
The wall graph does the surveying.
Junctions split where walls meet, corners mitre, collinear runs merge — and rooms are computed from the plan, not drawn by you. Walls know they are exterior or interior by themselves.
Draw a planIn plain words
Walls that know what they are.
You draw lines. The wall graph turns them into a building. Where two walls meet, the junction splits into T or X so each segment stays independent. Where two walls corner, the joint is mitred so the cladding reads clean. Where three runs lie on one line, they merge into one. From that graph the rooms are computed — every area, every perimeter, every wall classified exterior or interior by itself. Drag a wall and the whole plan re-derives in front of you.
"Living 22.4 m² · Kitchen 11.8 m² · Bath 4.2 m²"
rooms computed from the plan — drag a wall and every area updates
"wall ends mid-run — dangling end T-junction split"
the junction splits where walls meet; delete the wing and the wall heals into one run
Roofs & storeys
Four roofs, fitted to your perimeter.
No roof templates to wrestle. Pick a type and it auto-fits to the exact outline you drew — on one storey or two, over the garage bay or the passage.
Gable & hip
Gable and hip roofs fit the minimum-area oriented rectangle of your plan — the ridge lands where the geometry says it should. Set the pitch: gable roof 40° is one input.
Flat & shed
Flat roofs follow the outline exactly; shed roofs slope to it. Shed wedges — and modern-barn gable ends — infill with the siding you chose.
Storeys
Single storey, attic, or two full storeys. Levels stack on the same plan; the stair void is part of the graph, not a hole you cut by hand.
Foundation & slabs
The foundation and every floor slab follow the plan too — extend a wall and the slab extends with it.
Editing is a switch — and it starts OFF.
Editing is one capability. When a design opens — from a link, from a shared ?design= URL — editing is off, and the house looks the same to everybody. You arm it when you want to change something.
Open and look
A design opened from a link reads like a finished house — orbit, walk, play the day. No panels, no gizmos, no accidental edits.
Arm it
The Design door on the rail, the B key, or any tool key arms editing. Tools live inside the doors as tabs; nothing takes width from the canvas.
Change with a net
Undo/redo on Ctrl+Z/Ctrl+Y, F frames your selection, Ctrl+S saves. Tools on 1–9, the sun on 0, Space plays the day.
Put it down
Switch editing off and the design reads clean again. The switch is not remembered between visits — every session starts looking.
- Six doors on the rail: Design, Outside, Plan, Furnish, Light, Share — tools inside as tabs
- Tool panels where you need them: Walls, Openings, Roof, Terrain, Garden, Roads, Sun
- Grid, layer toggles and interior placement ghosting while you work
- Everything floats — the design IS the page, and the canvas keeps its width
- Every change lands as a scoped, undoable step
Draw four lines.
Get a house.
Rooms, openings, roofs and storeys compute from the plan. Free to start.