Slate hearth pad question

[NWbc Woodburner]

Am in the planning process of tiling my hearth with slate. I like the way the slate looks butted flush against each piece rather than the look of grout lines. Just wondering if anybody has 2 cents to put in about which way I should go, thinking because the hearth pad is just receiving a static load does not need the grout for strength (as opposed to foot traffic in a regular flooring application)?

Anybody have any advice they'd care to share? Any recommendations on sealers for a high heat area?

Thanks

 

[madison]

I would hazard a guess that the ember protection of ungrouted tiles is not like a solid surface or grouted tile.

Depending on the stove, you may need more than ember protection, so the design/construction must take that aspect into consideration. As well as, if you change stoves down the line to one that needs a certain R value.

Also I would consider tools and wood as not being static and could affect the slate.

 

[NWbc Woodburner]

Should have mentioned that the hearth pad below the slate is three layers of 1/2" cement board, a layer of sheet metal, and a layer of micore over a plywood base, so more than meets the R requirement of the stove.

 

[soupy1957]

When we were installing our wood stove, we were also in the beginning stages at that time, of a home renovation. There is a wall behind the stove that needed to be finished off.

First off, we had fire-retardant dry wall installed on the side of the wall facing the wood stove. Secondly, we wanted some sort of radiant surface, and like the look of brick (in our case) and so we had a professional Masonry person come out. We have him design freedom, only stipulating that he use brick.

What he came up with, was a backer board that is attached to the dry wall, and then (more specifically to your point) used half brick (thickness) with grout in between.

A couple of things here..........first off, using brick, seems to require grout, just because of the type of medium being used. It may be that slate doesn't need that, from a cosmetic point of view.

Secondly, I find in our particular application, that the wall behind the stove gets warm, but not HOT. I can put my hand on it during the hottest fire burn I can, without being burnt.

So this really boils down to what you like "visually" and what will hold up, long term.

I'm not a Masonry expert, so I can't say if slate without grout is less sturdy than slate WITH grout in between, but I CAN say that if your stove is one of the newer stoves out there, and if you are using Class A flue pipe (which allows you to be closer to the wall than a single wall flue pipe allows), you'll be closer to your wall than you realize ...............AND.................. you won't find ungodly heat build up behind the stove, causing worry over the integrity of the wall behind the stove.

Having said all that......with regard to using slate as a base ought to be fine. I wouldn't even worry about not using grout on that, as long as the slate is anchored in some way (I'm assuming there are multiple pieces, and not just one huge piece involved).

Then too, I was amazed at the fact that our Jack Russel could lay so long in front of our stove (relative to "heat") and so I went over and laid down at her level (basically putting my face on the floor), and was surprised how reasonably cool it was, at floor level! I'm not convinced the floor material is going to get excessive heat build up (heat rises, obviously) so it's really only about floor integrity, and resistance to burning.

I don't think I'd want my stove ("static" as it may be) to shift on me because of loose or non-anchored (grout or otherwise) base materials.



-Soupy1957

 

[offroadaudio]

If you use modified thin-set, that slate will not move - grout or no grout.

 

[NWbc Woodburner]

Thanks for the info guys. Going to do some more research although I am leaning towards installing w/o grout as it looks nicer with the slate I think.

I am installing a Jotul F3 into an existing fireplace, so no worries about backing the wall as it is existing firebrick.

Progress to date, slate just laid out to see how she looks:

 

[delp]

Hi NWbc,

I had a question about tiling my firebox not long ago on the forum and i was directed to a great site that you might want to check out:

http://www.johnbridge.com/

the forum section is filled with good folks with good info.

best of luck on your project!

 

[fishingpol]

There are a few others that have posted here about slate, as well a a few threads about it. Try a search for those. I did mine on a few inches of cured concrete, with a beefed up floor below. I used Vermont slate with 1/4 grout lines beween. It is beautiful stone. It does scratch a little, but a damp rag wiped over the area will "hide" the scratch. Deflection in the floor is the enemy. I used thinset to set the slate. My stove is not that heavy, and it is partially in the firebox, so there is not a lot of weight on it. I may be looking to upgrade to the F3 this year, but the weight difference should not be an issue.