Guide 03 · Measuring · Easy to avoid, expensive to make
The classic measuring mistakes, and how each one gets made
Nobody measures a window wrong on purpose. These ten mistakes are made by careful, capable people, usually in a hurry, usually with total confidence. Read the list once and you're inoculated against most of it.
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Measuring once
One width, one drop, done by smoko. Openings aren't rectangles, they're rectangle-ish, and a single measurement is a bet that you happened to pick the narrowest point. The fix: three places for width, three for drop, smallest wins. It's the whole first lesson of the measuring guide.
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Measuring the old blind instead of the window
Tempting: it fitted, more or less. But the old blind carries its own maker's deductions, its own fit type, and every error its installer made in 2009. You'd be photocopying a photocopy. The fix: measure the opening. The window is the truth; the old blind is a rumour about it.
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The deduction, done twice or not at all
A reveal blind must be narrower than its opening. If the form asks for recess size, the maker deducts; if it asks for blind size, you deduct. Guess wrong in one direction and the blind rattles in a too-big hole; guess wrong in the other and it never goes in. The fix: read the form's own instructions, decide whose job the deduction is, and do it exactly once.
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Centimetres
Order forms are in millimetres. The tape shows both. A "118.5" that meant centimetres becomes a 118 mm blind, which is a blind for a mouse hole. The fix: millimetres only, whole numbers only, write "mm" on the sheet once and never convert anything.
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The saggy tape
A fabric sewing tape, or a steel tape bowing across a wide span, reads long, sometimes by enough to matter. The fix: steel tape, held taut and level, a second person on anything wider than your arm span.
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Assuming the windows match
Six bedroom windows, same size by eye, one measurement copied six times. Then blind four turns out to be 15 mm narrower, and it's the one you notice forever. Same-looking windows routinely differ, in new estates as well as old terraces. The fix: every window gets its own row on the measure sheet. No exceptions for twins.
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Forgetting what lives in the reveal
Winders, handles, locks, flyscreens, the security screen's clips: everything that stands proud of the glass is depth your blind doesn't have. Measured past, they become the grinding noise the first time the blind drops. The fix: measure depth to the most intrusive object, not to the glass, and check the blind clears it for the whole drop. Reverse roll clears small handles; it doesn't clear a winder.
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Not checking square
The opening leans, the blind doesn't, and the difference arrives as a wedge of daylight at one bottom corner. Common in the inner suburbs' terraces and weatherboards, not rare anywhere. The fix: measure both diagonals; more than about 5 mm apart means read the face-fit rescue before ordering.
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Width and drop, swapped
1370 × 1194 instead of 1194 × 1370. The order goes through fine; the blind arrives as a wide, short letterbox. The fix: width first, drop second, every time, and say it out loud as you write: "width by drop".
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The unlabelled sheet
Nine perfect measurements, no idea which window is which. Now the ensuite blind is in the kitchen and both are wrong. The fix: name every row while you're standing at the window: "bed 2 left", not "window 7". Future you is not as good at remembering as present you believes.
If a blind has arrived wrong, don't cut it, pack it out, or "make it work". A trimmed roller loses its warranty, its hem and usually its dignity, and a packed-out bracket fails at the worst height to fail at. Get the supplier's advice on a remake, and next time measure once more and order once less. If the whole batch went wrong, that's exactly the moment the free measure earns its keep.
