How to measure

You need a tape measure and a 2 m spirit level. Measure once the tiling is finished — glass is made to the millimetre and can't be trimmed later. You measure the inside of the shower at the base and check the walls and the base with the level; the designer works out every piece of glass from that.

1. 1

   Measure the width at the base

   Tile face to tile face at the floor, hob or tray — wall to wall for a wall-to-wall screen; from the side wall to the inside face of where the return panel will stand for a corner screen; between the two return positions for a cubicle. Don't take anything off: the glass sits in a 2–3 mm bead of silicone that fits in the play of the base.

2. 2

   For corner showers, measure the return depth at the base

   From the back wall to the inside face of where the front glass will stand — the tray or tiled base size. We add the 10 mm glass thickness so the return runs past the front to the outside corner (900 inside becomes a 910 panel).

3. 3

   Check each wall with the level

   Hold the 2 m level on the tiles where the glass will go. If it sits flat, the wall is plumb. If it rocks or shows daylight, measure the gap under it with the tape and note whether the gap is at the top or the bottom. Enter that in the designer: a made-to-order panel is always cut on a rake to suit the wall; a stock-size panel stays square and takes up to 5 mm in the silicone, more than that and it is made to order.

4. 4

   Check the base with the level

   Lay the level along the base where each run of glass will sit — across the front, and along the return for a corner or cubicle. If one end is up, measure the gap under it and note which end is low. Fixed and return panels get a raked bottom edge so the top of the screen stays level; doors stay square and their 15 mm clearance varies a little instead. The same 5 mm rule applies as for walls.

5. 5

   Keep the height at 2000 mm if you can

   Height is the top of the glass above the highest point of the base. 2000 mm is the standard height and uses stock panels (the door is automatically 1985 mm so it clears the base and takes a drip seal). Any other height means every panel is made to order, which costs more. Bath screens are usually 1400–1600 mm.

6. 6

   Pick a stock door width

   Doors come off the shelf from 550 to 700 mm in 10 mm steps. The fixed panel takes up the rest of the width: we take off the 5 mm hinge gap between the door and its panel and the 5 mm closing clearance. Custom door widths are made to order.

7. 7

   Note hobs, niches and taps

   If the glass sits on a hob, measure the height from the top of the hob and tell us the hob height in the notes. Make sure the door won't hit a tap, towel rail or vanity when it swings. Doors can swing either way — pick the side that clears everything.