Parametric building design, in the browser.
Draw a plot, place buildings on it, and change a slider to rebuild any of them — massing, a facade with real openings, and metrics that show their working.
- Free, and no account. Nothing you draw is uploaded, and it keeps working offline once loaded.
- The same inputs give the same building. Every random choice runs through a seeded generator, so two options differ only where you changed them.
Courtyard · 3.2 m module
What it does
Eight tabs, in the order the decisions actually happen. Each one scopes what the viewport does, so the handles on screen are the ones belonging to the thing you are doing.
Open a tab to see the parameters it holds.
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Site
Draw the plot or trace it over a scaled map. Setbacks, separation, height and area caps — for the whole boundary, or a different figure per edge.
- Plot area and corners
- Setback, per edge or for the boundary
- Separation between buildings
- Height cap
- Plot ratio and coverage caps
- Location, and a map to trace
-
Placement
Put buildings on it, rotate and drag them. Clashes and corners falling outside the plot are found as you move.
- Add a building
- Duplicate one as a start
- Rotate and drag on the plot
- Clash and off-plot warnings
-
Massing
Six footprints, wings with their own depths, floors, cores, a setback top. Plus a freeform option the app labels experimental.
- Six footprints, plus freeform
- Wing lengths
- Wing depths, each its own
- Floors and floor height
- Parapet, and a setback top
- Cores — count, size, track
-
Program
Give a run of floors to retail, office or amenity. They take their own shopfront glazing and never a balcony.
- Retail, office or amenity
- A run of levels per band
- Shopfront glazing, no balcony
- GFA reported per use
-
Facade
Module width, windows per module, sill, reveal, balconies — and any elevation can differ from the rest.
- Module width
- Windows per module
- Window width and height
- Sill height, and reveal
- Balconies and their pattern
- Any elevation on its own
-
Units
A target mix by apartment type, reported against what the building actually fits, and the efficiency factor NIA is built from. The count is an estimate from the module width and the floor area, not a laid-out plan, and the app labels it one wherever it appears.
- A target mix by type
- Modules a flat spans
- Achieved share against target
- Efficiency factor for NIA
-
Drawings
Site plan, floor plan, elevation and section. Sheets are sized and drawn in millimetres, so printing at 100% gives a drawing a scale rule reads true — of the massing, with no speculative room layouts.
- Site plan
- Floor plan
- Elevation
- Section
- Scale, and a scale bar
-
Settings
Render mode — white, shaded or diagram — and a PNG of the view.
- White, shaded or diagram
- A PNG of the view
Above all of it: several design options in one session, each with its own undo fifty steps deep, saved together so a comparison survives the round trip.
Metrics that show their working
Every figure is computed from the geometry on screen and recomputed as you change anything. These are the real numbers from one scheme — an L-plan block of eight floors on a 9 900 m² plot — each shown with what it is made of.
The app's default scheme · 110 × 90 m plot
GFA
8 320 m²
footprint × floors — 1 040 × 8, the junction overlap counted once
Floors can be given over to retail, office or amenity rather than housing, and then GFA is reported per use and the unit estimate counts only the residential floors — before that, a retail ground floor was quietly counted as flats.
In the same pass, five planning limits — setback, separation, height cap, floor area ratio and coverage — are checked and reported with both numbers: the limit you set, and what the scheme does. A limit left at zero is off. Clashes between buildings and corners outside the plot are found here too, and the whole set exports as CSV.
Ten schemes, not one
A design option is a whole site — the boundary and everything standing on it. Switch between options, duplicate one as the start of a variation, and the metrics move with you, so a comparison is a number rather than a memory. Each option carries its own undo, and every one of them is saved with the file. Both below stand on the same 110 × 90 m plot, drawn at the same scale.
Option A three bars, five floors
- GFA
- 12 600 m²
- Coverage
- 25.5%
- Plot ratio
- 1.27
Option B a perimeter block around a court
- GFA
- 16 380 m²
- Coverage
- 33.1%
- Plot ratio
- 1.65
+3 780 m² GFA · +30%
Questions
Do I need an account?
No. There is no sign-up, no login and no trial. Open the page and it is there.
Where does my data go?
Nowhere. There is no backend to send it to. Everything is computed in your browser, and a scheme is saved by downloading a JSON file to your machine. The site you are reading sets no cookies and makes no third-party requests.
Does it work offline?
Once the page has loaded, yes — with two exceptions, and both only happen when you press for them: searching for a place, and importing surroundings to trace over. Those use Nominatim and OpenStreetMap's Overpass, neither of which needs an account or a key, and what goes out is a bounding box rather than anything you have drawn. Everything else works with the connection unplugged, including every export.
What can I export?
glTF for the geometry, IFC4 for a BIM model, measured drawings as SVG, the metrics as CSV, a PNG of the view, and JSON for the scheme itself. The IFC file carries storeys, slabs, walls, every window as a real opening, balconies and georeferencing; cores, the plot boundary and property sets are not in it yet, and it has not been through a Revit or ArchiCAD import.
Is it really free?
Yes, and there is no pricing page to read. It is a static page with no running cost behind it beyond hosting.
Is there AI in it?
No. It is parametric: you set the numbers and the geometry follows from them, the same way every time. The name is short for urban generator, and that is as far as the word goes — nothing here learns, predicts or invents.
Open it and draw a plot
It takes about a minute to find out whether it suits the way you work.