Expert: Steve Tavares - 10/20/2009

Question
QUESTION: Hi,
We are in the process of remodeling a room where there's a zero clearance fireplace.

The fireplace surround and hearth which were previously covered in an ugly ceramic tile will now be done in real slate slabs  instead.

Previous hearth was  constructed from ceramic tile glued directly over the wood floor, with only a 2" strip of  metal between the floor and the tiles. My question is...is it safe to apply the new hearth material right over the wood floor as had been done before? We thought hat perhaps it would be safer to install a wider metal strip (12" wide instead of the previous 2" wide) over the floor and under the stone.

Thank you in advance for your reply.

Maria C.

ANSWER: If this is a wood fireplace then you will need to have a hearth that is non-combustible (16" in the US, 18" in Canada) in front of the fireplace.

If it is gas then I would refer to the fireplace manual to see what needs to be there. Most gas fireplaces don't need a non-combustible hearth in front of it (there are a few that do), so you can put new hearth material in front of the fireplace without any issues.

Let me know how this goes please.

---------- FOLLOW-UP ----------

QUESTION: Dear Mr. Tavares;
Thank you for your reply.

Our Zero Clearance fireplace is a wood burner.

When they installed this Unit they sat the Unit  directly on the room’s wooden floor, and constructed the hearth as follows;

1) They first laid a 2” sheet metal strip over the wood floor directly in front of the Unit

2) They then applied the ceramic tile (which is a non combustible material) over that piece of metal and extended it out to about about 20” total into the room.

We are constructing a  new hearth  from real black State Stone, which also is a non combustible material. My question is… do we need to also use a piece of sheet metal as was done in the previous hearth instalation (sandwiched between the wood floor and the stone)?  If so, should we stick to the 2” size metal strip, or increase that to a larger metal strip?

Thank you in advance for your reply.

Maria C.

Answer
This now makes total sense.

If you want you can put in that 2" strip then put stone on top of it.

or

You can put in non-combustible board (Commonly called concrete board or Rhino Board) and then install the stone on top of that.

The idea is that if the mortar between the stone erodes/breaks up in a few years and you open the fireplace to put wood into it and a spark flies out into the gap it will not have the possibility of starting a fire.

Thanks for the more detailed explanation.

I hope this help you out.