alexo

Another of the inside from before they added foam. There were gaps visible to the outside on each bottom corner. How would this usually be addressed? I'm concerned because we've had 3 fitted already, all have bottom gaps ranging from 2-4cm. The fitters say they're all going to be like this, and are returning today. Should I get them to hold off and be insisting they replace the lot or is this overkill? Or would getting them to redo it with an airtight foam and then negotiating a discount be more like it? Thanks for the help.

This is the outside. They said they couldn't do the cills since they didn't have a part so cills not attached. I did think this was odd though since the cills are here on site. The fitter plans to put sand and cement mortar over the foam gaps I believe. I'll try to upload more pics of the inside before it was foamed. Essentially the window was sitting on a plastic rail approx 4cm high that I could see internally before they foamed it.

😆 good point. I’ll double check it’s airtight.

I’m rather optimistically hoping there is no gap at the top. By the time I’d seen it they’d already sealed the rest of the frame so I don’t know. I assumed they’d pushed it up as far as possible to leave such a large gap.

I’m not sure. I saw them drilling the frame in earlier for one. However another one has a strap poking through the exterior frame which was spotted late in the day and they said they would remove. This might be a fitting strap. They said this was a carry strap though. Will get a pic before they come tomorrow to show you what I mean. Are different types of foam required for frames or straps? Thanks

So you think this is an unacceptable gap? I don’t know what the max permissible or expected gap should be. On labcwarranty it says the maximum gap permitted for openings less than 3m is 10mm (per side). So 2cm would be fine if the gap is only at the bottom here. Whereas I have a 3.5-4cm gap. But I think this is guidance for new builds and new openings. I’m not sure if this is realistic for a retrofit?

I'm currently having some Internorm replacement windows fitted. All was going well when I saw them being fitted with compriband round the sides. However, once they were in I was concerned by the 4cm gap at the bottom between the frame and the blockwork below. The window is sat on quite a hefty plastic rail, and in the pics you can see the gaps in the corners to the outside. The exterior sills are yet to be fitted so I am hoping this might close some of the external corner gaps. The window fitters are planning to fill these internal gaps with expanding foam and then add a plastic trim at the bottom to conceal this. All three of our dormer windows have been fitted like this, with gaps ranging between 2-4cm. For context these are replacement for old dormer timber windows, and the surveyor who did the measurements mentioned there are often problems sizing for existing dormers. The window fitters have assured me this is normal for replacement windows and they've fitted many Internorm installations like this without issue. To me it seems pointless to pay for expensive passivhaus standard triple glazed units like this and push for compriband, only to have foam used in a large gap at the bottom. I've requested the fitters to try to use a piece of wide compriband at the bottom in addition to the foam that will go behind the trim. Is this gap acceptable and normal for a retrofit of Internorm or any windows for that matter? Thanks