Expanding foam to seal UPVC windows or patio doors?

26 Jun 2004
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United Kingdom
I am going to fit some UPVC French doors.

The rather vague instructions say that "expanding foam should be used in accordance with the instructions". It does not say if you should or should not use it.

Some UPVC window manufacturers tell you NOT to use it.

Mine, bought from Homebase, does not say anything at all.

Would most say its better to use it or not to?

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I have used it successfully on door and window frames, it forms a draught-proof seal and also sets and holds the frame in place firmly. However it needs to be protected from the weather, both because sunlight breaks it down, and I think it can get sodden with rain. You can use a silicon bead on the outside, or a wooden batten to match wooden frames or subframes. I expect you already know how sticky it is and how to inject it without sticky gobbets getting on the floor, walls and yourself.

Look for the drainage channels on your doors so you don't interfere with free draining.
Yes use foam, Insulates and fixes the frame.
Assuming your going to use a cheap diy can and not a pro foam gun then masking tape everything first! Those diy cans are pretty uncontrollable.
and I think it can get sodden with rain.

I must admit I've never been clear whether the common types of expanding foam are closed cell (waterproof) or open cell (not waterproof). Perhaps someone who knows can confirm.
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As far as I know from a bit of research in the past the single part types ie the squirty tins are all open cell. To get the closed cell type you need the 2 pack tins which you mix yourself and pour so not practical for filling gaps etc. Hope that helps.

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