New hearth build questions

[Revturbo977]

My first post! Hello everyone. My wife and I just bought a new jotul f400 for our house. We don't have a hearth in place so naturally I have to build one . I'm not much of a mason so I need a bit of guidance . This will be a raised hearth and because me stove has a bottom shield apparently I only need a non combustible surface. So I scored some very nice large slate tile. 24x24 and about 1.5 thick. They arnt very flat. One is about 1/2 thicker then the rest. Can these be leveled with just mortar? Also not sure about sealing and grouting and What process I'm supposed do go with. Any help would be great.

 

[begreen]

Here is the basic process. Screw down some 1/2" cement backer board like Durock or Wonderboard to a sheet of 3/4" plywood cut to the hearth required size. (It's ok to go larger if you wish.). Arrange the tiles with 1/4" tile spacers and cut tiles if necessary. Then use a notched trowel to create a bed of latex modified thinset for the tile. and set. Allow tile to set up overnight, then grout. Wipe off excess grout before it sets up. You may end up needing to level the stove legs slightly with metal shim under a low leg if the tiles are still uneven.

There is a lot of info on tiling on the internet and at big box stores like homedepot. Also there is a good tiling forum at www.johnbridge.com/ .

 

[Have maul will travel]

Thinset mortar will not allow you to compensate for a 1/2 inch variation in tile thickness. It forms a thin layer (hence its name) of a quarter inch max and usually less. You could try the "old fashioned" method of a thicker regular mortar bed in which the tile is embedded but it is not so easy (or reliable either when not done by pros) as the thinset method. I'm afraid I would get more uniform tile or slate from your local big box store and use those nice thick slate pieces outside as stepping stones somewhere.

You could also use metal shims as begreen suggested but they would detract a bit from your nice slate hearth, in my opinion.

 

[Revturbo977]

I went and re measured the slate and it's about 3/8 different . Im not a fan of the box store tile so I'm going to try and get creative with the base

 

[webby3650]

With natural slate you need to "custom" set each piece. Trowel out the thin-set as mentioned above, then you will need to "butter" the back of each piece of stone. It's very tricky but it can be done by a beginner. If its not right after the first set, get a flatbar and pry it up, add more thin-set until its right. Make sure to use thin-set that's modified with polymer.
After its all dry you need to carefully seal only the surface of the slate. Then grout it. Otherwise the grout will bond too easily to the slate making it very hard to clean up and even possibly discolor it. Don't let the sealer run down between the stones or it will prevent the grout from bonding. If your bed is going to be very deep, go with a medium set rather than thin set.

 

[Have maul will travel]

I would definitely use the medium bed mortar (sometimes called granite and marble mortar) as thinset is really not designed for that application. Mount your thickest piece first, thinnest last, adjusting "butter" as needed.
I did find some nice 1 foot squares of 3/8 inch slate that looked very similar to yours (reddish and golden brown accents) at my big box store a few years ago, they varied in thickness too, but nowhere near 1/2 inch. They worked fine under a gas soapstone heater stove using thinset.
That's what I was thinking of. Best of luck with the job.

 

[Revturbo977]

Thanks. These are not going to be cased in end. The slate will be over hanging the base a bit so the thickness was needed. Ill figure something out

 

[webby3650]

And this hearth doesn't need to be made movable like the premade ones. If you got 3/4" subfloor, just cut back whatever floor covering you have and attach the cement board right to the subfloor. Ideally you would bed the cement board in thinset, then screw it down using a 6"x6" grid. Don't go easy on the screws!

 

[Revturbo977]

That's my plan . This will be raised about 5 inches . I've already build a pretty sturdy frame. Just trying to figured out how to level these big tiles.

 

[webby3650]

It'll look great!

 

[Parallax]

Like you, I recently set out to build a hearth pad with no prior tiling experience. It was fun and it came out nice.

I used slate and some of the pieces are thicker than others. Did my best to level them but was only partly successful. Looks great anyway. Perhaps better because of the natural variation. I failed to seal before grouting and had to go back later and chip grout off the tiles. But the grout color I chose blends in well with the stone so, again, one doesn't really notice. Turned out awesome. Was way cheaper than buying a hearth pad and the finished product is nicer. Best of all, if a tile should ever crack, I can fix it.

Trust me, if I can do it, you can too. The people at Lowe's were really helpful and they cut a bunch of tiles at no charge. If there had been a charge, it would have been negligible. Entire project ran about $150. Could have easily shaved it down to $100.

Here's a photo:



And here's a photo with the stove:



Final thought: Be careful to follow the required minimum clearances. I needed 6 inches behind my stove, 4 on each side, and 16 in front. Your requirements will vary depending on the stove you choose and where you live.

 

[Revturbo977]

With the rear sheild I need to be 7 inches from the wall, but need 8 inches of non combustible floor in the rear. So I'm doing 10 in the rear 17 in front and 8-9 on the sides. Yours came out very nice

 

[Parallax]

With the rear sheild I need to be 7 inches from the wall, but need 8 inches of non combustible floor in the rear. So I'm doing 10 in the rear 17 in front and 8-9 on the sides. Yours came out very nice

Thanks. I'm really happy with how it turned out. I hope your luck is as good as mine. Glad you're on top of the clearances. Couldn't tell from that photo you posted with the stove sitting on four tiles.