Is my sealed unit 24mm or 28mm?
Measure the overall thickness of the unit with a glazing thickness gauge or callipers. About 28 mm is the common size for modern uPVC and aluminium windows, while 24 mm is generally the smallest used in uPVC. Older timber or aluminium frames may take thinner units.
How do you measure a sealed unit in the frame?
- Use a digital glazing gauge across the unit, taken from the edge where the bead has been removed.
- Check for markings on the spacer bar.
- If the unit is out of the frame, measure each pane and the spacer, then add them.
What are the usual build-ups?
A 24 mm unit is commonly two 4 mm panes with a 16 mm spacer. A 28 mm unit is commonly two 4 mm panes with a 20 mm spacer. Laminated or toughened glass changes the total, so always measure instead of assuming.
Why does thickness matter?
The unit must fit the frame’s glazing rebate and suit the bead. Too thin and it rattles or needs packers; too thick and the bead will not clip. Order width and height at the same time, measuring at three points as frames are rarely square.
MLI Building Products supplies sealed units and glazing products for installers in Worthing, with free delivery within 30 miles.
Need a trade price? Call the trade counter on 01903 262 636 or visit us at Unit 1, Friar Walk, Worthing. We offer free delivery within 30 miles.
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