Every shower glass panel starts as a flat sheet that will be cut once, toughened, and delivered to your bathroom in its final size. After toughening, glass cannot be trimmed, shaved or stretched — a panel that arrives two millimetres too wide does not get adjusted on site; it gets remade. That single fact explains the whole measurement process. The panel has to be right before it exists, and the only reliable description of “right” is the opening it has to fit.
This is how that opening is read: why it is never the simple rectangle it appears to be, what is measured and in what order, how templates and lasers each earn their place, and what tolerances are for. It is also why the rough dimensions you send us on WhatsApp — genuinely useful, and the right way to start — can only ever produce a preliminary estimate, never the final number. (What to do at your end before the visit is a short checklist of its own; this article is about the measuring itself.)
At a glance
- No bathroom opening is truly square: walls lean, corners drift and floors fall towards the drain on purpose — by millimetres that glass cannot ignore.
- Width is measured at three heights, because the three answers are usually different, and the panel is cut to the differences.
- Plumb and floor fall are measured, not assumed — they decide how the panel is shaped and how the door will hang and seal.
- Tolerances are deliberate gaps, sized so seals, hinges and silicone can absorb what the walls cannot give.
- Rough phone dimensions describe the idea of the opening; the measured opening is the specification the glass is cut to.
Why no bathroom opening is truly square
Stand in a finished shower and it looks rectangular: two walls, a floor, right angles everywhere. Measure it and the rectangle dissolves. A wall that reads perfectly vertical to the eye can lean several millimetres over the height of a panel — in at the top, out at the bottom, or bowing gently in the middle where the plaster and tile adhesive built up. The corner where two walls meet is rarely a true right angle; it opens or closes by a degree or two, which across a wide panel is the difference between a door that meets its seal and one that stands off it. And the floor is not level at all, by design: a shower floor falls towards its drain, so the bottom line of the opening is a slope, not a line.
None of this is bad building. It is normal building, within normal tolerances, in villas and towers alike across the UAE — developer-built and renovated bathrooms both. A wardrobe or a curtain can ignore three millimetres. A rigid sheet of glass in a rigid metal channel cannot: the panel meets the wall along its whole edge, and every millimetre the wall wanders has to be accounted for in the shape of the glass, the packing of the channel, or the tolerance allowed for the seal. That accounting is what measuring is.
Renovations add a second layer. Old tiles come off and take plaster with them; new tiles go on thicker or thinner than the ones they replaced; a tray is swapped for a tiled floor. The opening that exists today is the only one that matters, and it is measured as found — never copied from the panel that came out, because that panel was made for the opening as it was before the renovation changed it.
What is measured: width at three heights, plumb, floor fall
The measuring follows a set order, and each item answers a question the cutting list will ask.
Width — at three heights. The opening’s width is taken near the floor, at mid-height and near the top of where the panel will run. On a truly square opening the three numbers match. Usually they do not: a difference of three to eight millimetres between the bottom and top readings is unremarkable, and the smallest of the three governs where a fixed panel must fit, while the pattern of the differences tells the cutter how the wall leans. A door’s width is then set against the space the measurements leave for it — hinges, gaps and seals included — which is also where door size meets glass weight and thickness, the subject of our guide to 8mm vs 10mm shower glass.
Height — at both ends. For the same reason, height is taken at each side of the opening. A panel that runs to a ceiling or a bulkhead meets a line that may not be level; a bath screen meets the bath edge, which has its own slope along its length.
Plumb. A level — spirit or laser — is run up each wall the glass will fix to. Plumb decides two things: how a fixed panel’s edge must be cut or packed to sit tight against a leaning wall, and how a hinged door will behave. A door hangs from its hinges as gravity dictates; if the wall leans, the door’s swing and its resting position lean with it, and the hinge positions are set to compensate at measurement, not fought with at installation.
Floor fall and the bottom line. The slope of the floor or tray edge is checked along the line the glass will sit on. The bottom of a fixed panel follows that line, and a door’s bottom gap — the gap its seal has to bridge — is set from the highest and lowest points of the fall across its swing. A door measured on the assumption of a level floor drags or gaps exactly where the fall was ignored.
Clearances and fixing points. Finally, the space around the opening: the swing arc of a door against the vanity, toilet and towel rail; the slide path of a sliding panel along its wall; and what the fixings will bite into — tile over block, tile over board, the position of anything concealed behind the tiles that the homeowner knows about. A measurement that only sized the hole and ignored the room would produce glass that fits the opening and fights everything around it.
Templates and laser measurement
Two tools do most of the work, and they are not interchangeable. A laser measure gives fast, exact lengths between finished surfaces — the widths, heights and diagonals of a straightforward opening can be captured to the millimetre without a tape sagging or a second pair of hands. Diagonals matter more than they look: comparing the two diagonals of an opening is the quickest test of how far out of square it is, and by how much.
A physical template earns its place wherever the opening stops being straight lines. A sloped or vaulted ceiling, an angled wall, a bath edge with a curve, a notch around a step or a pipe box — shapes like these are traced full-size onto a template sheet laid against the actual surface, and the glass is cut to the template. The template is the opening, copied rather than described; for anything that is not a rectangle-with-lean, it removes the guesswork that numbers alone leave behind. Many jobs use both: laser for the dimensions, template for the one awkward corner the dimensions cannot describe.
Tolerances and what they absorb
If the opening is measured to the millimetre, why is the glass not cut to the millimetre? Because a panel installed with zero clearance would be a panel under stress. Glass expands and contracts slightly with temperature; buildings move slightly with theirs; and a toughened panel forced hard against tile on every edge carries that stress at its edges — exactly where toughened glass tolerates damage least.
So the cutting size is the measured size minus deliberate allowances, and each allowance has a job. The gap at a wall is taken up by the channel or by silicone, which flexes where glass cannot. The gap at a door’s edge lets the door swing without kissing the fixed panel beside it. The gap at the bottom is bridged by the door’s seal — the flexible strip whose whole purpose is to close a space that varies as the door moves and the floor falls. This is why the seals matter as much as the glass: our guide to shower seals and silicone covers how those last few millimetres are closed, and what happens when they wear.
Tolerances absorb the final fractions that measuring cannot remove. They cannot absorb a wrong measurement — a panel cut ten millimetres short leaks or rattles no matter how good the seal is, and a panel cut long simply does not go in. The craft is in the balance: tight enough that seals and silicone work as a finish, loose enough that the glass never carries the building’s movement. That balance is set at measurement, from the readings, panel by panel — it is not a standard deduction applied blind.
Why rough phone dimensions only ever give a preliminary estimate
When you message us, we ask for photos and rough sizes — and from them we give you a preliminary estimate from your photos that is honest as far as it goes. It cannot go further, for reasons that are now straightforward: your tape took one width, and the opening has three; your photo shows the wall, but not its lean; nothing in a message can report the floor fall under the door’s swing or the true angle of the corner. A price built on those numbers would be built on the rectangle the bathroom appears to be, not the one it is.
That is not a dismissal of the estimate — it is how every job properly starts, and for standard openings it is usually close. It is a statement of what the number is: a range around an unmeasured opening. The measurement visit converts it, replacing each assumed dimension with a read one, each unknown with a checked one.
The quote that follows is fixed because the specification is fixed — and the specification is the opening, measured. That is the sense in which a made-to-measure shower glass installation is measured first and priced second, never the other way round.
Frequently asked questions
Can I measure it myself and just order the glass?
You can measure, and your numbers are a useful starting point — but they describe the opening at tape-measure accuracy, in the places a tape easily reaches. A single width reading cannot capture a leaning wall or a falling floor, and glass cut from it carries the risk: if it does not fit, it cannot be trimmed after toughening. Self-measured glass is a gamble taken at panel price; the visit exists to remove it.
Why can’t you cut from the architect’s or developer’s drawing?
Because drawings describe the bathroom as designed, and buildings are finished by hand. Tiling thickness, plaster build-up and ordinary construction tolerance routinely move a finished opening by several millimetres from the drawn dimension — more than enough to make drawn-size glass wrong. The drawing is a guide to intent; the specification is the room.
What if my walls are badly out of plumb?
Then the panel is shaped and packed to the wall as it stands — that is the normal case, not an exception. Severe lean can influence the advice (a door’s hang, the choice between systems), and if the lean is beyond what glass and tolerances can absorb, you will be told at measurement, with the making-good options, before anything is cut.
Does measuring mark or damage the tiles?
No. Lasers touch nothing, tapes and levels rest against surfaces, and a template is a sheet laid against the wall. Nothing is drilled, marked on the tile face or fixed during measurement — fixings only happen at installation.
How exact is “measured to the millimetre”?
The readings are taken to the millimetre, and the glass is cut to those readings minus its tolerance allowances. The finished fit you see — even gaps, seals meeting along their length — is the readings, the tolerances and the fixing working together. Millimetre readings with no tolerance would fit worse, not better.
Talk to us about your measurement
If you are ready to move from rough sizes to a specification, message us on WhatsApp on 052 443 2655 with a wide photo of the shower or bath and your area. We will give you a preliminary estimate from the photos, then book the measurement visit — and the fixed quote follows the opening as measured, not as guessed.
This guide is part of our Shower Glass Installation series. Next: Partition, Enclosure, Cubicle or Screen? What Installers Actually Mean →
