how do you seal gap between external wall and gas flue?

[steviefaefife]

hi
Any ideas how to make a warterproof seal between the external wall and the gas flue, with the recent heavy rain we have had water coming back in to the house as there is around a half inch gap between the top of the flue and the wall?

cheers

[toptips]

hi,is this a new flue?get a bag of ready mixed mortar(sand and cement)and a pointing trowel.try and get the mix as far into the wall as you can.hope this helps .p.s. dont forget to add water to the mix.