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Step-by-Step Guide
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Measuring Guide

Accurate measurements are essential for a perfect fit. Follow our step-by-step guide to measure your existing frames for replacement sealed units.
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Millimetre Accuracy
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Gather these before you start measuring.

Expert Glazing, Done Right

We're not a national call centre. We're local glaziers who take pride in every job.

Tape Measure

A metal tape measure accurate to the nearest millimetre. Cloth tapes stretch and are not accurate enough for glazing measurements.

Pen and Paper

Record each measurement immediately. Note which window each measurement refers to — label them by room and position (e.g. 'Kitchen left').

Step Ladder

You may need to reach the top of larger windows to measure height accurately. Always measure from inside the property for safety.

Phone (Camera)

Take photos of each window you're measuring. This helps us identify any non-standard configurations and advise on specification.

Expert Knowledge

How to Measure for Replacement Sealed Units

Important: You're measuring the glass, not the frame. Replacement sealed units fit into your existing frame rebate, so we need the glass dimensions, not the overall window size.

Step 1: Measure the width

Measure the width of the existing glass pane from edge to edge, at the narrowest point. Measure in three places (top, middle, bottom) and use the smallest measurement. Record in millimetres.

Step 2: Measure the height

Measure the height of the existing glass pane from edge to edge. Measure in three places (left, middle, right) and use the smallest measurement. Record in millimetres.

Step 3: Deduct for clearance

Deduct 2mm from BOTH the width and height. This 1mm clearance on each side allows for fitting tolerance and thermal expansion. So if your glass measures 590mm × 1190mm, order 588mm × 1188mm.

Step 4: Measure the thickness

Remove a bead (the strip holding the glass in place) to expose the edge of the sealed unit. Measure the total unit thickness with a ruler or callipers. Common thicknesses are 20mm (4/12/4), 24mm (4/16/4), and 28mm (4/20/4).

Step 5: Check for special shapes

If your window is arched, angled, or any shape other than rectangular, contact us with photos and measurements. We manufacture bespoke shapes to your exact specification.

The most common error is measuring the frame opening rather than the glass. The glass sits in a rebate behind the beading — it's smaller than the visible opening. Always remove a section of beading to see the actual glass edge before measuring.

Common Questions

Frequently Asked Questions

Everything you need to know about our double glazing repair and replacement services across the South West.

  • We recommend measuring from inside for safety and access. You'll need to remove a bead section to measure thickness, which is easier from inside. The measurements should be identical from either side, but interior access is more practical.

  • If sealed units arrive and don't fit, we'll manufacture replacements at a discounted rate. However, toughened glass cannot be resized after manufacture — it must be remade. This is why we strongly recommend measuring twice and contacting us to verify before ordering.

  • Yes, and we encourage it. Email your measurements and photos to us before placing your order. We'll review them and flag any concerns. This free check has saved many customers from ordering incorrectly sized units.

  • Yes. Even windows that look identical may have slightly different glass sizes due to manufacturing tolerances in the frames. Measure each window individually and label your measurements clearly (room, position, width × height × thickness).

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