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Replacement windows - gaps around the sides.

  • 03-01-2023 11:55am
    Registered Users Posts: 2,340 ✭✭✭NUTLEY BOY

    Apologies if this in the wrong forum.

    Should there be much of a gap between the frame of newly fitted replacement windows and the window openings in to which they have been installed ?

    Looking at two local jobs done recently.

    In one case you can barely see any gaps at the edges.

    In the other case there seems to be gaps of about 1 to 2 inches filled with expanding foam. Is this a botch job caused by wrong measurements or is it acceptable practice ?


  • There should I think be a little gap (10 mm) at the sides & top to allow for adjustment— it provides a margin for error as well as allowing for an opening which isn't perfectly plumb etc. But the uPVC windows in my house are a very tight fit: the frames were literally hammered into place, which is fine except it eliminates any possibility of removing them whole & re-using them.

    A 1 inch gap anywhere filled with expanding foam is a joke. A 2 inch gap filled with expanding foam is hilarious.

    At a guess, the guy who did the job with the stupidly large gaps bought the windows at a knock down price because they were made the wrong size, not paid for, failed QC etc and were otherwise worthless to whoever sold them to him. Or possibly he measured the openings completely wrong and had a choice between losing thousands on the job and doing a ridiculously bad job.

    Either way, it's difficult to understand why it didn't cross the idiot's mind to mitigate the crappiness of the job through the addition of frame extenders or similar.

    The only thing which would excuse a 2 inch gap around the window frame would be if the opening itself was that badly crooked, and there was no real way of doing the job right. Even in this scenario, it's very hard to believe that there wasn't a significantly better way of addressing the issue than just filling a gap you could throw a ball through with expanding foam....

  • Registered Users Posts: 5,633 ✭✭✭10-10-20

    If they are retro-fits with a low impact on the internal decoration (removed old frames and fitted new ones from the front) then the width of the new window is limited by the reveal. That may have played a part here. We'd need to see photos to be sure @NUTLEY BOY.

  • Registered Users Posts: 3,058 ✭✭✭T-Maxx

    The detail at the gap is more important than the size of the gap.

  • Idiocy played a part here. Every single window in my house was replaced from the front with nil impact on the internal decoration. As were most of the windows in my estate. With no gaps.

  • I'm intensely curious as to what detail you believe would make acceptable a 2 inch gap between a window frame and the opening into which it was "fitted"?

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  • Registered Users Posts: 5,633 ✭✭✭10-10-20

    That's the ideal, yes. But I'd like to see the photos of what is being complained about so that we can make an informed opinion.

  • Registered Users Posts: 2,805 ✭✭✭Dr Turk Turkelton

    If your windows were fitted from the front then they were fitted by cowboys.

  • Registered Users Posts: 2,805 ✭✭✭Dr Turk Turkelton

    The window should be fitted from the inside against the brick/ block on the outside leaf of your cavity.

    If it's put in from the outside it has to be smaller than the ope which means all you have holding it in place is some mastic. I have seen this done before by a window company.

  • Registered Users Posts: 2,805 ✭✭✭Dr Turk Turkelton

    Here is an example of how a retro fitted window should go in from the inside:

    And here is an example of how a new build reveal should be rebated to allow the window to fit against the outside brick:

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  • My estate (early 1980s, so pre bulding regs & no relevant bye-laws) isn't built that way. Only viable way to install replacement windows is from the outside for exactly the reason you describe.

  • Registered Users Posts: 2,805 ✭✭✭Dr Turk Turkelton

    Sorry Bryson Whispering Pocketful but I don't understand you? How is putting them in from the outside the only viable way of doing it?

    Even if your house was built with cavity blocks there would have been reveals plastered on the outside which the windows should have been placed against from the inside.

  • "Even if your house was built with cavity blocks there WOULD have been reveals plastered on the outside which the windows should have been placed against from the inside."

    Replace the word "would" here with "should".... the reveals are on the inside, so only option for replacing windows is to place them from the outside.

    I didn't build the place (and wouldn't know how to detail the ope). To be fair, the first replacement window went in about 2 decades ago and there's been no issues.

  • Registered Users Posts: 2,340 ✭✭✭NUTLEY BOY

    Thanks to everyone for the input.

    I feel very much better educated about the potential perils to watch for as we will probably be replacing windows this year !

  • Registered Users Posts: 5,633 ✭✭✭10-10-20

    Just to clarify:

    Ideally fit the windows from the inside, removing the internal reveals so that they can be tight-fitted to the existing walls. The normal distance from frame-edge to inner leaf wall is 10mm, but it depends on how the outer reveal was plastered, so that might need some adjustment on either side. The trade-off is that you'll have to replaster and paint internally.

    Gaps between the window frame and walls are filled with a special window/door expanding foam and normally these are no more than the width specified above.

    If you're considering installing EWI (external wall insulation) in the future then consider doing the windows first and then EWI, but have the windows installed into the outer leaf and not the inner leaf as this closes off some of the thermal bridges once the EWI is installed.