I have old double-glazed windows where the frame doesn't allow easy removal of the window from the outside. I had problems with finding anyone who would do the replacement as it isn't as straight-forward as the newer style of window frame - it is pretty difficult to remove the white plastic pieces that press up against the inside of the window pane to keep it tight in the frame.

I made the mistake or ordering a replacement double-glazed window pane that was 5mm thinner than the original window. The thickness had been measured by my experienced Plumber as 25mm but when I went to the shop to order window, the shop owner said it would either be 24 or 26mm, so I went home and measured the thickness (whilst the window was still in place, on the first floor of my house) and got it drastically wrong.

Anyway, I am looking for something I can place in the gap, either between the white plastic piece and the window pane or between the plastic piece and the frame, so that the window is securely in place. Currently, I am using the double-sided sticky foam pads that came with the new window but with winter here, I need to sort this out permanently. I've read about wood being an option but would prefer something that is waterproof/plastic or rubber but I am not sure of what to get or from where.

I know I could just get the frame remade but at a cost of £75, I'd rather come up with a cheaper but effective workaround.

Some photos of the setup are here to help with seeing exactly what I'm describing...

how to window should look when it fits correctly a view of the gap between the window and frame view of the gap at a different angle a gap at a different angle the window gap again more of the gap another gap photo plastic piece

Can any one help?

  • You may be able to glue something to it since it is PVC. But a pic of the old and new sash would be very helpful, especially if the photo is of the edge of the window where it meets the frame, to show good detail. With the sash removed....
    – Jack
    Nov 22, 2014 at 15:50
  • Thanks @Jack - I've added a group of photos to show exactly what I see. Hopefully, this will make it easier for you to see the type of frame and the pieces that clip in between the frame and the window. The last 4 images are to show the PVC piece with the rubber on one side that is supposed to clip in and secure the windows tightly between the window and frame. Does this help?
    – delprimero
    Nov 23, 2014 at 22:52
  • Sorry I misunderstood. The pictures helped a bunch. I thought it was a replacement sash that was too thin for the jamb. Not the replacement glass in an existing jamb. I reread the post and seen my short coming, My answer will be long with options but none may be as good as a replacement glass the right thickness.
    – Jack
    Nov 24, 2014 at 2:56

1 Answer 1


There may be a possibility of finding thicker glazing strips to hold the glass in tighter. Window manufacturers sometimes use thinner glazed units in other windows they make, so if you can find the producer of the unit, you may find a glazing strip to cut to length that will hold it in. That is the better of the options I will suggest, although it may be really difficult to get it.

The other is to, I will write this with my head down and my eyes not meeting yours, metaphorically speaking, cause I think it is really a second rate way to fix it. That is, use silicone caulk to back the glazing to hold it to the seal on the outside. The biggest problem is the silicone will not press the glass against the seal to do the job it needs to keep the rain out. It will be messy if you are not familiar with caulking, especially with silicone, and the window may still leak because the pressure is not being applied to seal the window at the outside face. Laying the window down flat so the weight of the window is pressing the seal, then apply the caulk, let it cure, then set the window sash back in place in its jamb.

  • Thanks. I think I prefer the option of contacting the company to see if there is something they have. I don't know who made or supplies these but I know they are old because this type isn't really installed these days, due to the difficulty in removing windows from the frame with these plastic inserts. Would a black rubber spacer be an option... I could insert this between the plastic insert and the window as the insert has grooves that fit the window frame whereas the window facing side only has rubber. This way if the rubber made the fit tight enough, it would be waterproof. Worth a try?
    – delprimero
    Nov 24, 2014 at 22:35
  • Just to provide an update on my research, I've found wedge glazing strips that may fit into the gap between the PVC strip and provide a tight fit/seal. An example of what I'm talking about is this link I'll update later on progress once I double check what size I need to get (although 5mm should be fine).
    – delprimero
    Nov 25, 2014 at 15:18
  • All things considered, the main thing for the glazing strips to fit properly are to press the glass against the seal on the outside face of the glass. The gap is only on the inside face and a properly installed filler, with uniform, continuous pressure, should fill the need. By the way, the link only shown a shopping cart with nothing in it.
    – Jack
    Nov 25, 2014 at 16:09
  • sorry about the link. The correct one (on the same site referenced in my previous comment) is here. I've ordered the 6mm rubber gasket and will give that a try and report back. Another suggestion I've received back after emailing a few window parts companies is below.....
    – delprimero
    Nov 27, 2014 at 13:08
  • Two tier suggestion. Use a product called 'Gun Grade Foam' and then cover that with 28mm trim. The foam does need covering after using as it breaks down in UV light. Sadly we sell neither of these items via eBay (the gun grade foam is a hazardous product). Here's a link for the foam. you may have to copy and paste it into your browser to view - everbuild.co.uk/index.php?route=product/… Kind regards Paul. two47sales
    – delprimero
    Nov 27, 2014 at 13:10

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