Expanding foam and UV

[Pecanfan]

It says on the side of Wickes expanding polyurethane foam that, if used externally, it should be covered (with filler or mortar) within 7 days since it's not UV resistant.

Anyone have any experience of exactly *what* happens to this foam if it's not covered within 7 days?

I've just braved the elements for 3 days moving an external door - the new door is finally vaguely weatherproof (with a combination of expanding foam and frame sealant) but I really can't be arsed rendering & painting around it before the spring. Am I being foolish? If so, as a temporary measure, could I just paint the foam with some form oil-based primer?

Ta!

Andy

[Grunff]

The foam will initially darken in colour. In a few weeks, it will have hardened considerably, losing much of its flexibility. In a few months it will start to break up. A couple of years and it will be gone.

Painting it with a couple of coats of primer will stop this, but will make it difficult to render later.

[kdband]

I did pretty much the same thing last year, but only left it for a few weeks before finishing. Some discolouration did occur but that was about all. Mind you we weren't getting quite so much wind and rain at the time so no real opportunity for it to become waterlogged.

[Lobster]

I'd agree with all that but I think the 7-day deadline is unnecessarily short - bit of backside-covering I think! But I wouldn't wait as long as spring before covering it.

Hey, this sounds like a good excuse to cite Peter Parry's fantastic Expanding Foam Story, for the benefit of uk.d-i-y newbies, at:

A must-read!

David

(and NB to newbies: the rest of the uk.d-i-y FAQ is worth a read while you're in there...)