Corridor width is one of the few dimensions in a house where the tight version and the comfortable version are only 100 mm apart, and where getting it wrong is felt every single day. It is also cheap to get right, because a corridor's cost is driven by its length rather than its width.
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 walks it without thinking; two pass with a shoulder turn. |
| Comfortable corridor | 1000–1200 mm | Two people pass. Furniture goes through. What a house should aim for. |
| Where doors open in | 1000 mm | A door leaf swinging into the run needs the passage to survive it. |
| Accessible route | 1200 mm | With 1500 mm turning circles at changes of direction. |
| Entrance hall | 1500–2000 mm | Somewhere to stand, take off a coat and put something down. |
These are clear widths, measured between the finished wall faces, not between structural centrelines. On a plan drawn with real wall thicknesses that is simply what the room measures. On a plan drawn with thin lines it is not, which is one of several reasons those plans mislead.
Why 900 is the number
A person walking takes about 600 mm of width. Two people passing without turning take about 1100 mm. 900 mm is the compromise the conventions 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.
That last point is the one that catches people out. A 900 mm corridor turning 90° into another 900 mm corridor will not pass a long rigid object. A sofa, a wardrobe or a sheet of plasterboard needs the diagonal, and the diagonal at a 900 mm corner is short. If something large has to come round a corner, widen the corner rather than the whole run: a corridor that opens out at the turn costs almost nothing and solves it.
What doors do to the width
A corridor is rarely just a corridor. Doors open into it, and each one needs about 800 mm of clear floor on the side you walk up to it, so that you can stand, pull the handle and step back around the leaf. A 900 mm corridor supplies that, but only while nothing else is standing in it.
Two failures are common enough to design around:
- Doors opposite each other, both opening into the corridor. They foul each other and neither can open fully. Stagger them along the run, hang one to swing into its room, or widen the corridor to 1000 mm.
- A door at the end of a corridor, opening toward you. There is nowhere to step back to. Hang it to open into the room, or give the corridor end a wider pocket.
Sliding and pocket doors have no swing at all, which is exactly why they belong in tight corridors and small bathrooms. They still want the 800 mm of standing room on both sides. The full set of figures is in the standard door sizes guide.
An entrance hall is not a corridor
A corridor is a place you move through; an entrance hall is a place you stop in. Someone stands still to take off a coat, put down a bag, greet a visitor and open the door inward, all in the same 2 m². That is why 900 mm is wrong at a front door even though it is right ten metres further on.
Give an entrance hall 1500 to 2000 mm of width, and check three things in it: the front door has somewhere to swing that is not into a person, there is a wall for coats that the door does not cover, and there is a sightline that does not run straight into a bedroom or a bathroom.
When a corridor is too wide
Above about 1400 mm a corridor stops buying anything. Nobody passes more comfortably at 1600 mm than at 1200, and the extra 400 mm along a 6 m run is 2.4 m², which is most of a small bathroom. A wide corridor with nothing in it is the least productive floor in a house.
The exception is a corridor that is doing a second job. Line one side with 600 mm of shallow cupboard and a 1600 mm hall becomes a 1000 mm hall with a run of storage, which is a good trade in almost every house. That move, and five others, are in how to reduce wasted hallway space.
Checking it on a plan
Two different tests matter, and passing one does not imply the other.
- The narrowest point of the corridor, not its nominal width. A radiator, a boiler cupboard door or a boxed-in soil pipe can take 200 mm out of a run without appearing in the room's dimensions.
- Whether a route actually reaches everything. A corridor can be a comfortable 1200 mm and still fail if the only way into the utility room is past a door that opens across it.
Gridsnap tests both. Naming an area Hall, Corridor,
Landing, Entry or Lobby arms the 900 mm minimum-width
check on it, measured at the room's tightest waist rather than its overall size. Separately, the
route check floods the floor from outside the building and reports anything it cannot reach with
a 600 mm walking path. The 900 mm rule only fires on a room you have named, so an unnamed
700 mm corridor passes silently.
How much corridor a house should have in the first place is a different question, with a different answer: see how much circulation space a house should have.