Question: Along the entire length of the fireplace in the front/bottom portion, there appears to be slotted vents of some kind. I'm assuming this assists in the ventilation necessary to keep a fire burning. I want to raise up the hearth in front of the fireplace by using a 2x4 frame and a top layer of plywood. I will then tile. The problem is, if I do this, I will cover a portion (approx. 2/3)of the vent area at the bottom front of the fireplace. My questions are these: (1) Will this be OK or will this cause a ventilation problem resulting in smoke entering the house? (2)If it's OK for ventilation, does any heat come out of these vents (i.e. will I have a problem with the 2x4/plywood platform getting hot/burning)? Even if safety & functionality wise it would be OK, will this be against building codes? Answer: I'm going to assume that you have a pre-fab fireplace, as these units have the type of intake that you mention. In this case, it is very unsafe to cover these vents in any way. In fact, it could be said that you will almost surely have a house fire if you do. These vents represent that cooling system for the fireplace. Cool air enters the bottom vent, circulates around the fireplace and exhausts somewhere near the top. On most pre-fab fireplaces, all these areas are painted black - black areas cannot have any combustible materials on them or in front of them. You should not block any vent areas on Pre-Fab fireplaces. See your manual for more information.