How to seal gas biler flu into wall?

[Sarah_W]

I've just got a guy to fit a new boiler (3rd floor flat) and he's sealed the flu (from the weather) by injecting foam around it when it's sitting in the hole. DOes this sound right? I was expecting mortar/cement or similar although it is impossible to access outside???

[VxDuncan]

Not sure, but could start to smell real nice when the flue gets hot

[robinhood21]

VxDuncan said:

Not sure, but could start to smell real nice when the flue gets hot

The outer flue should not get hot as the inner flue caries the hot gases. The expanding foam is not the ideal solution but, being on the third floor would be a tad over the top to pay for scaffolding to do the job properly. I think most expandable foams are fairly impervious to the elements so should be OK.

[Wings]

I used Kos Fire Cement, small tin costs about £1.49, apply then just before setting, smooth with a damp sponge.Heat resistant, can be painted and drilled etc. etc.

[BGB autosport]

Depends what foam he used, you can get high temp stuff specially for putting around flue liners.