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Housing - Renovation: Should windows be installed with any kind of DPC or similar?

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    Hi

    I recently had some new windows fitted.  The old ones were wooden and very much on their last legs with plenty of rot.  Think they were installed in the 70s.  Th new ones are aluminium.  The fitters simply removed the old, put in the new, and foamed the gaps around where the windows meet the walls.  

    I really don't know much about windows, and have been looking into this but not finding any answers...  Should there be any kind of damp proofing, barrier, or anything along those lines between the walls and windows?  Or have they done it right?  I note that the old windows had a kind of thick type of felt above them and bedded into the walls, but this was cut away during the fitting. 

    Can anyone please tell me if I'm worrying about nothing or whether there should be something there?

    Many thanks
    • CommentAuthorMike1
    • CommentTimeOct 9th 2022 edited
     
    When used this way, the DPC is there to isolate the timber from the potentially damper wall, to reduce the chance of the timber rotting. With an aluminium window, rot isn't a risk, so no need for a DPM. You don't mention it, but presumably they have used mastic to seal between the window and the wall too?

    Posted By: greenfingerI note that the old windows had a kind of thick type of felt above them and bedded into the walls, but this was cut away during the fitting.
    The same piece of DPM was (since purpose made insulated cavity closures now serve the same purpose) often used to isolate the external leaf of the cavity from the inner leaf, before being wrapped behind the window. That's probably what they cut back, and it shouldn't be a problem.
  3.  
    That's a relief to hear - thanks for putting my mind at ease.

    I should have added that they are in solid walls (not cavity). But by the sounds of it, rot is the potential issue and as that only applies to wood the wall construction shouldn't make a difference.

    I've just had a thought though / remembered something...

    Last year when I did some tidying up around other windows (uPVC), there was some black plastic DPC around them. What purpose would that have been serving?

    Let me see if I can find a pic...

    Thanks again
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      IMG_20211111_180708655.jpg
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      IMG_20211111_181531739.jpg
    • CommentAuthorMike1
    • CommentTimeOct 9th 2022 edited
     
    Posted By: greenfingerLast year when I did some tidying up around other windows (uPVC), there was some black plastic DPC around them. What purpose would that have been serving?

    A 'tray' to the sides and sill of the window is sometimes used as an extra measure to ensure that any water that makes its way between the window and wall is diverted to the outside. For example I _always_ specify one on a dormer window, linked to the lead flashing below the sill, where you need a 100% guarantee that there will be no water ingress. I've seen multiple failures where this hasn't been done.

    In your case, with a solid wall, I'd guess that the installer was just being extra thorough.
  7.  
    Thanks Mike.

    Sorry for not being clear and giving the relevant info, but the uPVC window in the photos above (and other uPVC windows in the house) are in standard cavity walls.

    It's only the new aluminium windows that are in solid walls, and that have been fitted with nothing around them other than foam.

    Apologies, I should have said that before.
    • CommentAuthortony
    • CommentTimeOct 9th 2022
     
    Should be fine.

    Slightly worried about the above felt as it could direct water in the wall over the top of the window to outside.

    Bottom line is no problem
    • CommentAuthorrevor
    • CommentTimeOct 9th 2022
     
    In addition to the foam have they weather sealed the outside joint with a mastic. Did they use mechanical fixing or just the foam. How is the interior joint been finished, pay attention to sealing to avoid draughts. Foam is neither weather or draught proof in my experience.
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    Thanks tony, that's reassuring.

    All good questions revor. The external wall is being re-rendered around the windows. No sealant, just the render (lime). Is that sufficient?

    And we are doing the decorating inside. So all good on that front.

    As for mechanical fixings, yes, they are screwed to the walls. But that does lead me to a couple or related but off topic questions...

    1. Is there a specific part of the frame you should screw through? On one of the windows they have put some screws through the frame and others through the thermal break. Does that matter?

    2. Is screwing too close to the corners a problem? The tech manual says to keep ??mm fromth corners, but thy have gone a lot closer. As much as 50mm in some places. Does that matter.

    Great help everyone - thank you all
    • CommentAuthortony
    • CommentTimeOct 9th 2022
     
    I like to see packers at each screw.

    I would seal outside before render

    I seal inside with acrylic sealant before making good, it is good to get rid of draughts first.
    • CommentAuthorrevor
    • CommentTimeOct 10th 2022 edited
     
    <blockquote><cite>Posted By: tony</cite>I like to see packers at each screw.

    I would seal outside before render

    I seal inside with acrylic sealant before making good, it is good to get rid of draughts first.</blockquote>

    Totally agree.

    Frames are normally fixed in the glazing rebate or via straps internally and plasterboarded /plastered over so cannot be seen. If you have external exposed screws, then make sure they are A4 stainless and if you can put an epd washer under the head and sealant on the shank/thread to avoid galvanic corrosion.

    The usual spacing for fixings is 150 mm from the corner but your windows may be different.
  13.  
    Thanks for the replies and help. Let me see if I can find a photo of the window with the screws in different places... Nothing was used with the screws as far as I can see, just straight in.

    As for the fixings and distance from corners, Origin specify: "Frame fixing should be between 100mm to 150mm from the external corners." The installation video shows him measuring from the internal corners. And Origin weren't able to confirm which is right!

    As for the installers have actually done... The distance from corners varies from window to window and corner to corner. In the closest instance they are 50-60mm from corners (measuring inside the frame). The furthest is 165mm from the corner. That's on a different window I should add.

    Hopefully it's nowt to worry about, but thought I'd just check.

    Thanks a million
  14.  
    Just to save further confusion, three of the windows were fitted in the old part of the house (solid walls), whereas this one is in the newer part (cavity walls). Not that it matters for where the frame fixings are, but thought I'd mention it so as not to confuse some of the above!
      Frame Fixings in Different Part of Frame.jpg

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