DG Units In Sash Windows

20 Dec 2006
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United Kingdom
Hello all. Looking for a bit of advice regarding my windows:

I have a Victorian house which has sash windows. At some point, a previous owner has had the single pane glass replaced with very fine double glazed units. However the units look as though they have take a single pane of glass, the correct size for the window, and then stuck a second pane on top, however the second pane is smaller than the first so it doesn't actually go into the frame, if you follow. This leads to a nasty looking seal going all the way round each window pane. Over time these have deteriorated significantly and look messy.

So, I know one option would be to get new windows made up which are designed to take proper double glazed units, but that is out of the question due to cost. The window frames are in great condition, so it would be a waste.

So what I was wondering, was if it would be possible to modify the beading (the bit that holds the glass) on each window frame to accommodate a thicker double glazed unit.

Would this be possible or would it look daft/be structurally unsound?
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sounds like you have "stepped units", where one pane is larger and sits in the rebate as designed, the other smaller one inside the house. the gap around this pane and the spacer then needs to be covered, outside (very important to stop UV degradation of the seal) and inside (for aesthetics).
it is unlikely you will be able to modify the rebate or beading enough to fit a conventional sealed unit. if you refit stepped units make sure that the spacer is completely covered from the outside, this could have been your problem.

another possibility is slimlite units. these are dear and i don't really approve of bedding them without drainage - ask them what warranty they offer.
Stepped! That's the name! Damned if I could remember it :)

So do stepped units do as good a job as say slimline DG units? If those are my best bet then I don't mind sticking with them as long as the seal doesn't look too bad and lasts.

Thanks for the reply.
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if installed correctly (as described above) they will outlast slimlite units in my opinion.
you will be able to get top spec (Ug = 1.1) units for a reasonable price.

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