How to measure an alcove for a sliding wardrobe
Six measurements, in the order you actually take them. A kitchen forgives — a cabinet shifts, a filler hides the rest. Sliding doors do not: the track runs straight, the wall does not, and every difference stays visible as daylight between door and wall.
One rule, and everything else depends on it
Take every measurement in three places and write down the SMALLEST. An opening that is 2404 mm at the bottom and 2411 mm at the top is not a 2411 mm opening. Doors are made to the smallest measurement, because a door that fits the narrowest point fits everywhere — one that only fits at the top cannot come down.
What you need
- A 5 m tape measure
- — steel, not a tailor's tape — cloth stretches and lies by several millimetres
- A spirit level, and a long batten if you have one
- — a sloping floor is invisible to the eye and carries the whole wardrobe
- A pencil and this form
- — six measurements in three columns are not something you remember
- A second pair of hands
- — for openings over 3 m — a sagging tape reads longer than the wall is
The six measurements
1.Width of the opening, at three heights
Measure wall to wall at floor level, at mid height and at the ceiling. Write all three down and circle the smallest. Below 900 mm sliding doors make no sense — two doors would be narrower than a pair of shoulders, and a single sliding door has nowhere to go.
What it decides: It gives the number of doors and the width of each one, and decides whether you need two tracks or three.
If you get it wrong: The doors arrive too wide to fit between the walls, or they are made to the widest reading and leave a gap at the bottom you can see straight through.
2.Height, at both ends and in the middle
From the finished floor to the ceiling. If there is a cornice, measure to the cornice and note that separately. Above 2400 mm a side panel no longer comes out of one board, so the wardrobe splits into a lower part and a top box — not a problem, but it has to be known before cutting.
What it decides: Door height is the opening height minus the track system. The same measurement decides whether a top box is needed.
If you get it wrong: The door is made too tall and will not go into the track, or too short and leaves a slot above it that nothing covers.
3.Depth — back wall to the face of the opening
Measure from the back wall to the line where the doors will sit. Below 600 mm a hanger will not go across and clothes hang at an angle. From 620 mm it is comfortable. Sliding doors and their tracks take roughly 90 mm of that depth — the inside is that much shallower than the alcove.
What it decides: Whether sliding doors are possible at all, whether drawers fit, and whether the rail runs across or along.
If you get it wrong: A wardrobe shallower than the threshold is ordered with sliding doors, and only afterwards does it turn out that hangers sit at an angle and the doors brush against the clothes.
4.Floor fall along the whole opening
Put the level on the floor against the back wall and walk it the full length. Note which way it falls and by how much. With no long batten, measure floor to ceiling at both ends — the difference is the fall.
What it decides: The plinth is packed and levelled BEFORE anything goes on top of it. Everything above rests on that plane.
If you get it wrong: The carcass is built on a sloping floor, the bottom track runs off level, doors slide open or shut by themselves, and the gap under them is not the same end to end.
5.What the ceiling is, and whether it holds
Knock on the ceiling along the door line. Plasterboard sounds hollow, concrete and render sound dead. If the ceiling is suspended, find out at what height the structural slab is and whether there is a batten the track can be fixed to.
What it decides: With top-hung doors the upper track carries the entire weight — with a mirror that is over 30 kg per door.
If you get it wrong: The track is screwed into plasterboard alone, the plugs pull out within months and the doors come down. It is the only mistake on this list that can hurt someone.
6.Everything that intrudes into the opening
List and measure them: plinth and skirting, radiator, switches and sockets, boxes, pipes, the door frame and any bulge in the wall. For each one write down how far it comes into the opening and at what height. A 40 mm filler absorbs most of them — but only if it is known in advance.
What it decides: Whether the wardrobe runs to the wall or stops short, and where the filler goes. A door that touches the skirting cannot close.
If you get it wrong: The wardrobe is ordered to the bare wall measurement and then cut on site, or it ends up standing off the wall because a socket is in the way of the doors.
A check that costs two minutes
Measure both diagonals of the opening — bottom left to top right and the other way. The difference tells you how far out of square the opening is.
| Difference between diagonals | What it means |
|---|---|
| up to 15 mm | A filler absorbs it. Carry on measuring and write down the smallest readings. |
| 15–30 mm | You need a filler on one side, and that is planned up front, not on site. |
| over 30 mm | The wall gets straightened, or a fitter comes out. Sliding doors cannot hide this much. |
If you want a mirror
A mirror in a sliding door must be safety-backed (film bonded to the rear), 4–5 mm thick. The film holds the shards together if it breaks — plain mirror in a door that is pulled every day is not a question of whether, but when. Ask the glazier for the thickness and the backing explicitly; the price is theirs and we do not show it.
Once you have the six numbers
Enter width, height and depth into the planner. It works out how many doors fit, how wide they are, how many modules go inside and exactly what has to be cut.
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