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Gap around boiler flue needs filling... Best product to use?
- Thread starter c0tt0nt0p
- Start date
Chillybean
Well-Known Forumite
You could use expanding foam, however I would use brick mortar on the outside if brick and plaster on the inside less messy..
c0tt0nt0p
Well-Known Forumite
There's a rubber cover on the outside which is securely attached for the moment, internal is far worse as the pic shows.... I've been warned off using foam even the fire retardant stuff....
Gramaisc
Forum O. G.
Expanding foam can make a huge mess, if things go wrong. It is breathing in on the outside of the pipe, so heat isn't serious issue. Rockwool plus filler/plaster seems a reasonable approach. If the rubber cover is in place outside, then it should stop a lot of the draught. Just the air entering via the mortar joints is all you should be getting.
Chillybean
Well-Known Forumite
Good point about air entering along the mortar joint, just had a look at mine and there's definitely a gap, will seal it tomorrow.
Rikki
Well-Known Forumite
Fire retardant foam isn't technically to regs, supposedly it's not air tight so won't stop products of combustion entering the building from the flue exhaust.
However most boiler manufacturers state the rubber collar externally is an adequate seal for these purposes. So you may not have a problems regs wise, it depends on what the installation instructions say.
TBH if I come across it I've always got a bit of ready mix in the van and just patch it externally. Internally it's just cosmetic as far as I'm concerned and not a safety issue. But some may choose to make more of an issue out of it.
I tend to use the fire rated foam but leave/or cut back so it's an inch or so back from the finished face. Then use mortar behind the rubber to brick face externally and either decorators filler, plaster or mortar internally. Boiler flues tend to come with a white rubber for the internal side these days so you don't need to get a brilliant finish as it's covered.
If the engineer thought it was actually creating a draught back into the building the products of combustion could also be entering. If this was the case they should have been asking for permission to cap off the boiler.
However most boiler manufacturers state the rubber collar externally is an adequate seal for these purposes. So you may not have a problems regs wise, it depends on what the installation instructions say.
TBH if I come across it I've always got a bit of ready mix in the van and just patch it externally. Internally it's just cosmetic as far as I'm concerned and not a safety issue. But some may choose to make more of an issue out of it.
I tend to use the fire rated foam but leave/or cut back so it's an inch or so back from the finished face. Then use mortar behind the rubber to brick face externally and either decorators filler, plaster or mortar internally. Boiler flues tend to come with a white rubber for the internal side these days so you don't need to get a brilliant finish as it's covered.
If the engineer thought it was actually creating a draught back into the building the products of combustion could also be entering. If this was the case they should have been asking for permission to cap off the boiler.
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