suitable materials for filling gap around flue

[ambrosia]

Doing landlords i frequently come across flues with large gaps around them where they pass through walls that have never been filled in,
sometimes theres those rubber collars hidding the hole, but often you can look along the flue to daylight
(occasionally on bigger holes i see newspaper stuffed in by the tenant to stop draughts)

I dont why hole are so common, maybe some engineers meant to return to make good others are just plain lazy. needless to say its not really exceptable


to make good, with a small gap i've seen engineers use silicon to seal the hole and on larger gaps expanding foam

logically both would work, both can be purchased with heat resistant qualities, both are hard wearing and should last, and both should stop any air flow or transfer of unwanted gases

however in my gas book it says flues should be sealed with sand and cement, with no mention of any other suitable products.
Is foam and silicon a no no

 

[dave1]

I work for a HA and I'd say at least 50% flues are not made good it's ridiculous poor workmanship in my opinion. I'd cement them in... However have seen them made good with silicone and other products.

 

[Barry98]

Don't some books read a suitable material ? Yet another grey area in our trade lets not forget the outer flue if twin lined is only air flow in

 

[stokecity]

when i do istalls i stitch drill quite tight, soim notgoin gooutand buy a bag of sand and cement which ive then ot to carry round with me, when i can just use some heat resistand silicone which ive already goton the van

 

[stokecity]

typing in the dark so there sum mistakes in that last post haha

 

[tamz]

typing in the dark so there sum mistakes in that last post haha

Are you under the stairs? Sun still shining here but just going down.

 

[GrahamM]

Are you under the stairs? Sun still shining here but just going down.

Or hiding from the wife in the cupboard? Maybe he short of her housekeeping money for the week.😀

 

[grahamgas]

when i do istalls i stitch drill quite tight, soim notgoin gooutand buy a bag of sand and cement which ive then ot to carry round with me, when i can just use some heat resistand silicone which ive already goton the van

Who still stitch drills in this day and age?

The last time that I had to was on an install in Paulsgrove. cast concrete walls as hard as nails, with rebar. Core wouldnt even touch it.

As to the OP, I have used all methods exp. foam can be wasteful if using tins, as it would have to be a big gap to use a whole tin.

Sand and cement is my preference.

But then how do you seal the outside wall on a sixth floor install, when flue has been put in from the inside?

 

[tamz]

I took the baby kango to one on monday. Bloody nofines and i wasn't loosing the tooth off a £100 core bit drilling it.

 

[AWheating]

I work for a HA and I'd say at least 50% flues are not made good it's ridiculous poor workmanship in my opinion. I'd cement them in... However have seen them made good with silicone and other products.

i worked on simular work, in the end i went around and disconnected and labeled them, gave the tenant the comapny phone number and told them to phone and complain that the boiler is dangerous and has been turned off. Once the HA get wind of the compliants they will start to get patched or the work passed to another company......... give them a quote 😉

 

[AWheating]

an unpatched flue (std flue) is AR unless allowed by the manufacture imo. either patch it or turn off and quote for the patching.

 

[neily01]

speaking to our local vokera breakdown engineer about this very subject and he use fire cement to seal around flues if not done and the gap is not to big. i thought not a bad idea quick and easy, [messey stuff] but not to sure how it will react with the lack of heat?

 

[REDSAW]

i use pre mixed tile adhesive if i have some scrags left over from a bathroom job, keep it in a tub and last for ages. takes 2 mins and sticks like ......,sure its heat proof?.

 

[tamz]

speaking to our local vokera breakdown engineer about this very subject and he use fire cement to seal around flues if not done and the gap is not to big. i thought not a bad idea quick and easy, [messey stuff] but not to sure how it will react with the lack of heat?

It still hardens, just takes longer.

 

[stevetheplumber]

when we was busy we carried a bag of sand and one of cement

 

[MK_Swans]

Expanding form (I used the gun grade) keeps for ages and no mess and you can cut it back/sand it once cured.

 

[Barry98]

when we was busy we carried a bag of sand and one of cement

Bag of ready mix ,

 

[Backboiler]

I do lots of landlord checks and I'm alarmed by the quantity of wobbly flues/chimney's that are left by the installer. They have drilled a 127mm core, stuck the flue through the hole and left it! It's for that reason I carry a old fashioned sweet tub full of readymix mortar and I seal it at no extra charge. Peace of mind.

 

[ambrosia]

and I seal it at no extra charge. Peace of mind

WHAT!!!
really :angelsad2:

i must be over charging, i normally make that into an hours work and hand out a £70 bill plus parking

 

[stevetheplumber]

Bag of ready mix ,

works out bloody exspensive that way about a fiver for 100kg of sand and cement fiver for 10kg redimix

 

[Backboiler]

WHAT!!!
really :angelsad2:

i must be over charging, i normally make that into an hours work and hand out a £70 bill plus parking

Yeah. It take 10 mins max. That probably why I do loads of Landlord checks

 

[neily01]

thanks for that, sounds like its worth having a tub in the van

 

[Mickyplumb]

As someone said, expanding foam but need to make sure it's the fire stop type

 

[gasmanrob]

if your using expanding foam make sure the boilers turned off!

A bloke in sidcup was told his boiler wasn't up to standards last year as his flue was not sealed through the void, so being a builder he thought i know ill whack some expanding foam in that. boiler fired up as he was squirting it in, the fumes from it got sucked in the intake and blew the boiler to bits case and combustion box. (was a profile) and the fella suffered 3rd degree burn as the can blew up in his hands.

Wouldn't use it myself been to a few jobs where someone had put to much in and as a result it squeezed on the flue causing it to crush a little and pull it out of its seal. why risk that for the sake of a bit of sand and cement. i keep a mortar gun on the van so if i cant get a trowel in a can load that up and pretty much inject it in.

 

[mfgs]

Bag of ready mix ,

I have always got a bag of ready mix in the van.