# Hey all....Ditra Question for a Hearth



## CMSStoneworks (Mar 23, 2009)

Whats going on guys. Figured I would come and get some opinions. I am wrapping up a fireplace that I did with travertine. Have to do the top portion with 18x18" and then down to the non existent hearth. It was an existing fireplace that never had a hearth and the firebox was open on the left side. We removed the steel column and bricked in the left side, making it uniform. We framed (steel studs) and put up our durarock which got tiled over. Everything is going great. 

After I finish the top and grout the entire structure (and dont need the scaffold anymore, its a 12 ft ceiling), I plan on building a hearth. The firebox as is is already 13 inches off the wood floor, so it doesnt have to be 4 inches thick. The customer would like to keep it around 1-1.5" thick. My tile is 3/8". The substrate is tongue and grooze wood. Deflection? Have no idea. Im learning as I go. I can take a look under the floor before building it, but lets just say the beams are 2x10's 16" OC. I was thinking about using a half inch piece of ply for rigidity, topped by a sheet of 1/2" durarock, and tile over it. 

MY questions are, is this the best option? If so...How should I fasten the ply to the existing wood flooring? (The customer and I both dont want to have to cut the flooring out) I was just going to screw it down with some liquid nails in between. 

My second thought was to use a sheet of 1/2" durarock on top of the substrate, fasten it down, then go with a layer of ditra, then my tile. I have never used ditra yet, so im not sure about it in this application. 

My second concern is having combustibles within that hearth. If i were to do 2 layers of 1/2" durarock im worried about the rigidity of the structure, and possible grout and tile cracks if the hearth is stepped on continuously or a log is dropped on it, etc. But obviously it would be completely non combustible. 

I feel like the ditra would be the best bet. But want to hear your opinions first. BtW, Im using Tec full flex, not that it matters much.

Thanks in advance guys!!! I also have one other question, which i will address in another post to minimize confusion.:clap:


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## JohnFRWhipple (Oct 20, 2009)

We build a lot of fireplaces here in Vancouver and I have never used ditra under a hearth.

Over shiplap back in the day they installed building paper and a skim coat of slurry mud.

You can install building paper over the shiplap and then do a 1 3/8" float of mapecem Screed Mortar. 14 square feet per 1/4" of lift.

You could add a 5/8" plywood overtop and then go Ditra XL.

You could add 5/8" plywood some Noble Seal TS, hit it with modified thinset, a little mortar mix, back butter the slab or tile with modifed this set - tap tap tap - level

JW


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## angus242 (Oct 20, 2007)

Little confusion here.

Is the current wood (T&G) the subfloor or the finished floor? OP makes it sound like finished hardwood. John is talking ship lap (subfloor). 

I think it's finished hardwood. If that's the case, I would tile directly over it...not even with a layer of ply/CBU over it. It needs to come out.

Once the finished floor has been removed, either the plywood or deck mud ideas would work. I have no idea if there is any restrictions with Ditra by a fireplace. NobleSeal has none. Install the NobleSeal with modified thinset and it's all good.


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## CMSStoneworks (Mar 23, 2009)

yea the substrate is finish hardwood flooring. The customer didnt want to cut it out but if there is no way around it, then it has to come out. I was hoping to add something over it and then tile onto that. but I would be worried about flex with traffic around the hearth moving the substrate, hence why i thought ditra may help. But looks like Im on the wrong track here...hmmm


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## CMSStoneworks (Mar 23, 2009)

Maybe I should tell the client we have to go thicker to prevent any deflection or flex and pour a small slab right on top of the floor? like 2 inches thick or so. I dont know. I feel like im being a hack regardless of the construction method here. I just cant help but think there is a better solution to this.


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## angus242 (Oct 20, 2007)

I would not do anything directly over the hardwood.


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## CMSStoneworks (Mar 23, 2009)

best way to go about cutting that section of hardwood out? Im not a carpenter, aside from the usual finish stuff and some framing. I cant say ive ever had to cut out hardwood floor though. Makes me awfully nervous.


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## angus242 (Oct 20, 2007)

Protect floor with painters tape. Circular saw, plunge cut. Finish corners with a jigsaw or oscillating tool.


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## CMSStoneworks (Mar 23, 2009)

angus242 said:


> Protect floor with painters tape. Circular saw, plunge cut. Finish corners with a jigsaw or oscillating tool.


Thats what I figured. I guess I just need to use a finish blade, tape like you said, Cut slow, then finish up the corner with my rigid multimax. That should do it.


OK, now that we understand that the flooring will be coming out.....Lets start over. What kind of underlayment, if any? Poured concrete? PLywood? hmmm...

I have the money to play around with on this job so thats not an issue. I want to install the BEST option and best quality. I dont settle for call backs.


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