Can a stone slab hearth be installed directly on a hardwood floor?

[Suzu]

Dear Hearth.com Community

I hope everyone is keeping themselves warm in this cold weather specially if you have a stove or fireplace.

My husband and I are waiting for our new wood insert, Alderlea T5 Majolica Brown from Pacific Energy, to be installed soon. Our old tiled hearth started falling apart some time ago and since this model has its firebox sticking out to the front, we need to extend the depth of the hearth to meet the code. We thought this is a good opportunity to extend its width to align with the mantel to 78”, so that we can put firewood there or so on. I have attached a photo of our hearth, with tiles and transitional floor pieces, which means the hearth is slightly elevated from the floor.

We are going to install the hearth by ourselves before the insert and would really really like to avoid cutting the floor board to make the hearth foundation bigger as well as tiling work. I’ve seen many hearth photos online of natural stone slabs (with/ without transitional floor trims), or concrete slabs which seem to be sitting directly on a hardwood floor. I thought some of them might be just for display-purpose only, not legitimate installation, however, with a hope to minimize our workload and a love for its look we went ahead and ordered a granite slab in 78"W X 24-1/2"D X 1-1/8" H. Although I have seen slab hearths being installed into a cut out on the floor with mortar underneath on several how-to websites, my rough plan is as below, and here I need your advice;

1. Remove all the hearth tiles and transitional floor pieces and clean the area. By this we will gain enough depth for the foundation to meet the code.
2. Slap some kind of mud (cement or mortar?) into the area to fill the hole and make a leveled floor.
3. Put a tar paper across the floor to cover the area where the slab will sit on, maybe or maybe not, with 1” smaller on right, left and front than the actual slab size.
4. Lay one or two sheets of cement board to cover the tar paper.
5. Apply mortar onto the cement board and put down the slab.
6. Come up with an idea on how to finish the edges of the cement board and do it, with some kind of trim.

My husband has reasonable DIY skills, but he wants to cut any possible corners for this job, saying he is seriously considering just applying mortar on the whole area, over the old tiles and hardwood floor, hoping the mortar will do leveling the floor, and put the slap on top. Even to me it doesn’t sound quite right, but if it is acceptable, I wouldn’t argue with him.

So, if anyone can help us, what will be the easiest and quickest way to install a slab hearth in our situation? I am also curios of what is the proper way and why.

Thank you for your time and attention in advance, looking forward to hearing back from you!
Stay warm!

Suzu

 

[Simonkenton]

I can't answer your question but I love the idea of your new hearth. A six foot wide granite slab.
Somebody else will come along and give you the tech details.

 

[bholler]

Well you are talking about a permanent hearth extension which means it needs to be built to code for an open fireplace. That means on a self supporting slab of concrete with no combustible materials contacting the bottom of it. That is allot of work. It is much simpler if you make a "temporary" hearth pad that technically could be removed if anyone ever wants to go back to an open fireplace.

 

[xman23]

I guessing here. Shouldn't the hearth be built as specified by the insert manufacture? I did something similar when I installed my stoves hearth with hardwood floors.

 

[bholler]

I guessing here. Shouldn't the hearth be built as specified by the insert manufacture? I did something similar when I installed my stoves hearth with hardwood floors.

If it is a permanent part of the fireplace it needs to be built to code for a fireplace.

 

[begreen]

The T5 just requires ember protection. bholler's suggestion of just laying in the stone is good. It's not permanent and as long as it is one piece there is no risk of embers falling through the cracks. It will be one very heavy piece of stone, so the caveat is that there is nothing acting as a leveling compound to provide even support.

 

[rwhite]

Just make sure the floor is level. If you build one yourself I would build it in place. Not only do they get heavy fast, they will conform a bit as your building and may hide some of the unlevelness of your floor. For ember protection only you can stack hardiboard to desired thickness and tile however you want. Another DIY idea is to form it up, lay plastic on the floor and pour a stained concrete hearth. Or just oil the heck out of the floor to prevent it from sticking.

 

[bholler]

Just make sure the floor is level. If you build one yourself I would build it in place. Not only do they get heavy fast, they will conform a bit as your building and may hide some of the unlevelness of your floor. For ember protection only you can stack hardiboard to desired thickness and tile however you want. Another DIY idea is to form it up, lay plastic on the floor and pour a stained concrete hearth. Or just oil the heck out of the floor to prevent it from sticking.

That would be safe but technically not code compliant because it would be permanent.

 

[rwhite]

If you have a release agent on the floor or some type of barrier to prevent the concrete from adhering I dont see the difference from a stone slab. And you'd have the advantage of the concrete forming to the unevenness.

 

[begreen]

If you have a release agent on the floor or some type of barrier to prevent the concrete from adhering I dont see the difference from a stone slab. And you'd have the advantage of the concrete forming to the unevenness.

I was wondering about that. A tiled hearth on plywood, cement board should be ok too as long as it is not attached. But it too should be on a level surface unless 9/8" plywood is use.

 

[Suzu]

Thank you so much, everyone, for your advice. I feel more comfortable with the project. Maybe I should ask this in a different thread, but has anyone have installed or seen a brown enamel insert or stove against a black surround or black wall? We ordered the insert only by photos and have never seen the color in person. I am thinking of using black marble mini subway tile for the surround with black grout, hoping the combination works fine. The mantel is painted white.

Thank you again for your advice and comments!

Suzu

 

[begreen]

More important than color, make sure that the stove's clearance to the mantel are honored.

 

[Geoff C]

If you have a hearth extension that is already code compliant for an open fireplace but need to extend it further for ember protection of an insert can the further part be permanent?

 

[rwhite]

I dont think a black surround would look bad. After I had built my last surround I got to wondering what one would look like that had a metal frame with tiles in it. Would have to come up with something so they could be slid into the frame somehow.

 

[rwhite]

If you have a hearth extension that is already code compliant for an open fireplace but need to extend it further for ember protection of an insert can the further part be permanent?

Not and have it up to code, from the way I read it.

 

[Suzu]

Thank you, everyone, specially for concerning our code compliance.

The installation will be done by the dealer/ a professional and we are following his advice to prepare the hearth and surround so that they will meet the code. Therefore, I believe we should be OK for code wise.

Thank you, rwhite, for your comment. In my ideal world, my black tiled surround is framed with brass trim as the hearth is Titanium granite, black base with veins in white, gold, brown. The closest product I can think of is a brass tile edging but tiles don't slide in it. If you can find such product or develop one by Monday, please let me know! I am thinking of just tiling first and applying trims later, if I can find any, for decoration purpose only "within the code!".

By the way, or more importantly, I am a bit discouraged to find out there is a fissure in the granite where the firebox's leg will rest on. So the fissure will be under the firebox although the firebox doesn't seem to have a direct connection with the stone. I am wondering what will be a likelihood for the fissure to develop into a crack overtime or if there is anything we can do to reduce the risk. I understand there is always a possibility that it may crack.

It is extremely cold today. Everyone, stay warm!

 

[bholler]

I dont think a black surround would look bad. After I had built my last surround I got to wondering what one would look like that had a metal frame with tiles in it. Would have to come up with something so they could be slid into the frame somehow.

Technically no. But it should be safe that way

 

[rwhite]

Technically no? Not understanding.

 

[rwhite]

I dont think it would be to difficult to come up with a brass frame work that tiles could slide into. I've screen shotted some channel as well as corners and Tees that could be used to join it all together.

 

[bholler]

Technically no? Not understanding.

I mean technically extending the hearth in that way will not meet code. But from a practical standpoint I don't see that it poses any safety risk and I seriously doubt many inspectors will ever know the difference. But you would be taking a chance because I am sure there are a few inspectors who would catch it and fail you.

 

[rwhite]

Gotcha, it was the quoted portion that threw me off. You quoted the post where I was talking about the surround.

 

[bholler]

Gotcha, it was the quoted portion that threw me off. You quoted the post where I was talking about the surround.

I see that now and understand why it didn't make any sense. Sorry

 

[Geoff C]

Thanks for the info