UPVC window gap advice

Discussion in 'Builders' Talk' started by Scott Ldn, Jul 22, 2021.

  1. Scott Ldn

    Scott Ldn New Member


    hoping someone can offer some advice. Recently moved into a property and discovered the UPVC window has some sizeable gaps around its edges. Being on 3rd floor. Access is somewhat limited so haven’t been able to assess top/bottom of window. However, the need properly sealing.

    i was thinking to apply expanding foam within the gap void and then either attach some kind of trim, or cover in mortar in to the frame. What’s the preference?
    I have attached some pics. Sorry the aren’t ideal but it’s tricky to get a decent pic (using a selfie stick out 3rd floor window!)

    Attached Files:

  2. quasar9

    quasar9 Screwfix Select

    Yes, expanding foam, upvc trim and silicone sealant between trim and masonry.
  3. Scott Ldn

    Scott Ldn New Member

    Ok thanks got the quick reply! Best get it done while the weather is good.
  4. Scott Ldn

    Scott Ldn New Member

    Also, just wanted to ask. I reckon the gap is about 20mm. Should I got for trim exactly the size of the gap or gor for something slightly wider? Thanks in advance
  5. quasar9

    quasar9 Screwfix Select

    20mm is that all round or total of two sides ?

    What most window fitters do is use a trim that’s oversize by 10 - 15 and superglue the trim onto the frame. The trimmed foam won’t hold it. Effectively the trim is being held by the frame ( so you need enough overlap for a good bond) , covers the foam ( which is not weatherproof and degraded by sun) and sealed against the wall by a bead of silicone.

    the skill lies in choosing the right size trim ( or trimming it to size) and making the whole assembly look even and part of the window.

    if you are renting, ask the landlord .
  6. Scott Ldn

    Scott Ldn New Member

    20mm is the gap on each side. The frame isn’t quite flush with the wall unfortunately so I think it’ll have to be stuck at an angle. So I should go for something 10mm wider, glue that to frame to hold it then silicone both sides of trim to seal
  7. quasar9

    quasar9 Screwfix Select

    Some people may suggest simply siliconing the trim in place. It may work but not my choice !
  8. Jimbo

    Jimbo Screwfix Select

    The trim will come lose from silicone after a while. Also need to consider the flow of water down the elevation as it looks like the frames are right to the front of the render pretty much. So the top detailing will be important to stop the water running behind the trims at the side.
    Scott Ldn likes this.
  9. Scott Ldn

    Scott Ldn New Member

    Thanks for the tip. Got some mitre Bond to fix it and some Uninond weather guard sealant for around it

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