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Paper-strip test on window weatherstripping: how much can it tell you?
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After a big temperature swing, a draft can make it hard to tell whether the weatherstripping has flattened or the sash isn’t seating evenly. What do you look for along the seal to spot wear or gaps without pulling the weatherstripping out? And how much does it matter whether the sash closes and locks normally?
I’ve heard of using a strip of paper to compare how firmly a closed sash holds it at different points. Is that a useful rough check, or can sash hardware and window design make the results misleading? I’m curious what would point toward simple weatherstrip maintenance versus having someone assess the sash alignment.
2 replies
A paper strip can show a difference in grip, but it won’t tell you why. With the sash closed, look for weatherstripping that’s visibly crushed, cracked, displaced, or missing in one section. A local defect points more toward the seal; uneven contact across a broader area, especially if the sash also resists closing or locking, makes sash seating worth assessing.
The comparison only means much if you’re testing similar spots with the sash closed the same way. A cam lock or compression seal can pull the sash tighter as the lock engages, and the meeting rail or corners may pinch paper differently just because their shapes differ. So I’d compare like with like, rather than treating a stronger grip at one unlike spot as evidence of an alignment problem.
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