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

Pecanfan wrote:
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?


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.


--
Grunff

In article , Grunff
writes
Pecanfan wrote:
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?


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.

Also it's not a closed cell foam so it will soak up moisture like a sponge
which could lead to rot problems in the future. I'm very careful where I use
it.
--
fred

fred wrote:

Also it's not a closed cell foam so it will soak up moisture like a sponge
which could lead to rot problems in the future. I'm very careful where I use
it.

I've heard this said quite a few times, but I'm really not sure. Think
about how it's formed - lots of bubbles of propellant expanding away in
a PU matrix. I'd say it is largely closed cell, with only a few through
paths. Its moisture absorbance is quite low.

--
Grunff

In article , Grunff
writes
fred wrote:

Also it's not a closed cell foam so it will soak up moisture like a sponge
which could lead to rot problems in the future. I'm very careful where I use
it.

I've heard this said quite a few times, but I'm really not sure. Think
about how it's formed - lots of bubbles of propellant expanding away in
a PU matrix. I'd say it is largely closed cell, with only a few through
paths. Its moisture absorbance is quite low.

Yes, logic suggest this, but embarrassing stories win over logic every time:

Chum decides to make boat dock pontoon out of fibreglass and, to guard
against flooding in case of damage, fills it (them actually) with expanding
foam. Inevitable damage does occur and pontoon sinks faster than you can
say impervious steam liner :-)
--
fred

In article , fred writes
In article , Grunff
writes
fred wrote:

Also it's not a closed cell foam so it will soak up moisture like a sponge
which could lead to rot problems in the future. I'm very careful where I use
it.

I've heard this said quite a few times, but I'm really not sure. Think
about how it's formed - lots of bubbles of propellant expanding away in
a PU matrix. I'd say it is largely closed cell, with only a few through
paths. Its moisture absorbance is quite low.

Yes, logic suggest this, but embarrassing stories win over logic every time:

Chum decides to make boat dock pontoon out of fibreglass and, to guard
against flooding in case of damage, fills it (them actually) with expanding
foam. Inevitable damage does occur and pontoon sinks faster than you can
say impervious steam liner :-)

On reflection (this was a while ago), I think it was wave action breaking
over the pontoons, rather than damage, that ended up with them
waterlogging, but they definitely ended up sinking.

But (back on topic) I agree that short term exposure, of a matter of weeks,
will do no harm
--
fred

In article ,
Grunff writes:
fred wrote:

Also it's not a closed cell foam so it will soak up moisture like a sponge
which could lead to rot problems in the future. I'm very careful where I use
it.

I've heard this said quite a few times, but I'm really not sure. Think
about how it's formed - lots of bubbles of propellant expanding away in
a PU matrix. I'd say it is largely closed cell, with only a few through
paths. Its moisture absorbance is quite low.

I used it as replacement insulation on bottom of a freezer after
the initial fibre matting became waterlogged (or rather, ice logged).
I also assumed it was closed cell and wouldn't need any further
surface sealing, but I was wrong, although it did take about 3
years before it became completely water/ice-logged.

--
Andrew Gabriel

On Tue, 18 Jan 2005 19:30:30 +0000, Grunff wrote:

I've heard this said quite a few times, but I'm really not sure. Think
about how it's formed - lots of bubbles of propellant expanding away in
a PU matrix. I'd say it is largely closed cell, with only a few through
paths. Its moisture absorbance is quite low.

It's effectively open cell, just slow. It doesn't matter if it's a
"mostly closed" cell foam, if you need it really sealed.

If you use the two-part foams, not the squirty can stuff, there are
grades of those that are real closed-cell foams.
--
Smert' spamionam

Grunff wrote:
Pecanfan wrote:

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?


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.

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:
http://www.diyfaq.org.uk/humour.html#foam 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...)

Lobster wrote:

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:
http://www.diyfaq.org.uk/humour.html#foam A must-read!

David

hahahah. even if it's not true that's hillarious :-)


RT

I'd say you can leave a vertical surface exposed to sun and rain for a few
months. Eventually you need to fill and seal, having excavated any crumbly
stuff.

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?

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.