"Bob" wrote in message
.uk...


I have recently moved into a house, where there is a large gap around the
combi flue (i.e hole has been made, but never finished off). Can I used
expanding foam to fill this gap, or do I need to use mortar?


You can, but I'd use mortar. If you do as you plan you really need to cover
it with something such as a trim ring. PU Foam is not UV stabilised and
will deteriorate in the sun. It is also soft and hardly a great external
finishing material.

--
Mike W