Sealing around boiler flue internally...

[TommmC]

Hi Guys,

I bought a house in May and kept noticing cavity wall insulation balls in my kitchen. I didn't think much of it but after discovering a mountain of the stuff yesterday, I have realised they are coming from the gap around the boiler flue...

If it is windy or the extractor fan is blowing, it is disturbing the balls. The ring plate doesn't sit flush and the balls are coming out from behind here. I pulled the plate off to find a pretty substantial gap around the flue that was never sealed.

Is there a reason that this wouldn't have been done, other than laziness and am I safe to fill this in? Everything I've read online indicates it should be sealed!

What is the best stuff to use and is this DIY-able?

[TommmC]

I would attach photos but don't seem to have that permission yet!

[RGG]

Not the best photo but this looks like your solution -



Figure 2 shows a cruder example of yours, I would guess.
Figure 1 shows a competent solution.

I found it here -

https://registeredgasengineer.co.uk/technical/tech...

I didn't read through fully - it promotes a sand cement mix - I think.

[Simpo Two]

Or stove sealant perhaps? I've used the black version successfully indoors.

[tux850]

TommmC said:

If it is windy or the extractor fan is blowing, it is disturbing the balls.

I somehow skipped over the first sentence and went straight to this. Without any context I thought this was a euphemism for saying it was making you feel cold.

As for your question though, personally I would cement around the flue. A ready mixed tub of mortar that you just add water to would suffice.

[GasEngineer]

tux850 said:

TommmC said:

If it is windy or the extractor fan is blowing, it is disturbing the balls.

I somehow skipped over the first sentence and went straight to this. Without any context I thought this was a euphemism for saying it was making you feel cold.

As for your question though, personally I would cement around the flue. A ready mixed tub of mortar that you just add water to would suffice.

Should be sealed with sand/cement mortar mix as Tux says.

It is worth also checking that the outside is sealed. If the installer missed the internal seal they may well have not sealed the outside. (should be same sand/cement mortar seal).

[blueg33]

Ours is sealed with Fire Cement. Buy it ready mixed from Screwfix etc