900 mm is the minimum corridor width and 1000–1200 mm is what makes a house feel normal to walk around. Below 900 mm two people cannot pass and furniture cannot be carried through; above about 1400 mm a corridor stops earning its floor area. Gridsnap works to two separate numbers: a 600 mm walkable route must physically reach every door, every piece of furniture you have to stand at and the foot of every stair, and an area named as a hall or corridor is flagged below 900 mm wide.
The widths
| Route | Width | What it is |
|---|---|---|
| Absolute squeeze | 600 mm | One person sideways past an obstruction — a pinch point, not a corridor |
| Corridor minimum | 900 mm | One person comfortably; two pass by turning |
| Comfortable corridor | 1000–1200 mm | Two people pass; furniture goes through |
| Accessible route | 1200 mm | With 1500 mm turning circles at changes of direction |
| Between furniture and a wall | 600 mm | A secondary route round a bed or a sofa |
| Main route through a room | 800–900 mm | The path you actually take across a living room |
| Passage through a doorway | 800 mm | See door swings |
Why 900
A person walking takes about 600 mm of width. Two people passing take about 1100 mm without turning. 900 mm is the compromise the standards settled on: one person walks it without thinking, two pass it with a shoulder turn, and a 1600 mm mattress goes round a right-angle corner in it — just.
The corner is the part that catches people out. A 900 mm corridor turning 90° into another 900 mm corridor will not pass a long rigid object; if that matters, widen the corner rather than the whole run.
How Gridsnap tests a route
The plan check rasterises the floor at 100 mm and floods it from outside the building, so circulation naturally enters through an exterior door with no guessing about which door is the front one. Walls block, furniture blocks, stairs block; doorways are cut out of the walls; chairs are exempt because they pull out.
Blocked cells are then inflated so that a free cell means a person fits. The calibration is deliberate and worth knowing: a 600 mm gap always passes and anything under 500 mm always fails. Between those two it depends on where the grid lands, which is acceptable for a warning.
Reaching a specific thing is judged more softly than a main route, because the last step of an approach may be tighter than the corridor that got you there. A face counts as reachable when a route cell sits within 1000 mm of it with a clear line of sight; within 600 mm only walls have to be clear, beyond that furniture has to be out of the way too.
What has to be reachable
Every door, the foot of every staircase, and the working face of anything you stand at:
Front only — sofa, armchair, desk, TV bench, toilet. Either face — wardrobe, fridge, stove, sink, kitchen counter, appliance, basin, shower, bath. A symmetric unit satisfies the rule from either side, which also forgives a plan where its nominal rotation faces the wall. Beds — either long side, or the foot.
Gridsnap checks this automatically
The rule is no-route, part of the Pro plan check. Its findings read
“no comfortable walking route reaches this door”, “no clear route to stand at
the wardrobe” and “no clear route to the foot of the stairs”. When no door at
all is reachable it collapses to one message — “no entrance reaches this plan
from outside — circulation starts at an exterior door” — because blaming every
door and sofa individually hides the actual cause.
The 900 mm corridor figure is enforced separately, by room-size, and only
on an area whose Name matches hall, corridor, koridor, esik,
entry, landing or lobby. Rooms Gridsnap detects on its own are called
Room 1, Room 2 and match none of those, so rename your corridor or the
900 mm check never runs on it.
What this doesn’t do
- The route check guarantees 600 mm, not 900 mm. An unnamed 700 mm corridor passes the plan check completely. The 900 mm rule only fires on an area you have named as a hall.
- It does not report the narrowest point of a route. It answers reachable or not; it will not tell you where a route pinches or by how much.
- Turning circles are not modelled. Nothing checks the 1500 mm clear circle an accessible route needs at a change of direction, or in a bathroom.
- It is a single-storey check. Routes are traced per floor. Whether the stair actually lands somewhere sensible on the storey above is not tested.