hi i bought a new stone fire place to fit over an existing grate complete with granite hearth & a granite insert that fits between the stone pillars & below the stone lintle which is nicely topped off with a granite mantle ,you get the drift my question is the granit insert which incorporates the opening for a gas fire there will be a void of 0.100mm or so between the brest & the back of the insert i was just going to brick this up but what about a lintle do i use a spanlite across the top ,if so
1: how do i allow for any expansion between the granite & the fire back
2: do i point it up the virtical joints with sand/lime/cement, or fire cement.
my problem is the sprigot from the new gas fire will not protrude into the flue as far as the original as that one was fixed flush to the brest & the hot gasses will be vented just below the the lintle is there a special lintle or
please help.