Best mastic to seal around a metal flue, and hopefully brickwork too?

[happytotryit]

I have 2 small sources of leaks on my roof and I'm confused by the array of mastics available.

Can any recommend a repair mastic most suitable to seal around a stainless steel flue which is flashed with lead?

There is also a crack in some rendering nearby letting in water, so if the same mastic would adhere to cement render / brickwork as well, that would be very useful! Otherwise, what would work for that?

Obviously I'm after longevity and ease of application.

Thanks.

 

[footprints]

Best stuff for lead will also stick to brick, only thing is does it come into contact with a hot flue pipe? Not sure on its heat range a call to the makers is the best idea.
https://www.toolstation.com/lead-ma...MIuN7pmtT45QIVgrHtCh3ZzQd1EAQYASABEgLdAfD_BwE

 

[happytotryit]

Thanks for that, I'll check it out. The lead is 'wrapped' around the flue pipe, but I have no idea if it is hot at that level (about 4 or 5m above the gas fire).

 

[Alastairreid]

It will be twinwall so should be cool enough to use silicone.