Does anyone know if you need to leave a gap between an iron fascia and a timber mantle? We recently had a zero clearance direct vent fireplace installed and there was some question of needing beading to fill the gap between the mantle and the fascia, but then the builder said it was okay he just moved the firebox forward. This left a 5mm gap between the fascia and the mantle which he said they always leave in case the iron gets hot. But I noticed On one side for 10cm at the bottom the fascia is flush with the mantle and it looks much better. I have felt the fascia and it doesn't get hot. Does there really have to be a gap or can it be flush?