Approved Doc J is what you want. I believe it is 150mm gap around the sides OR a heat protected surface to the side walls. I would guess bricks count as a heat protected surface so it can be as narrow as you want.vicky whitworth said:Aren't there rules about how much hearth you have to have to front, back and sides of a woodburner? 3" either side sounds a bit tight to me. I thought it was more like you had to have 6" in case the logs rolled out and set the house alight. Vicky