OT: Installing Durock tile underlayment for wood stove... need to know correct side to use?

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Hi,
I'm building a ceramic tile pad for a wood-burning stove that'll be installed next week. I have a 3/4" particle board foundation and a sheet of 1/4" Durock underlayment for the ceramic tile. The Durock has a smooth and rough side. Which is the correct side to lay the tile onto?
Thanks, Jon
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On 28 Oct 2003, Jon B. spake unto rec.woodworking:

    If you examine the edge of the Durock, you'll notice that the smooth side has a thin layer of cement on it. That's the side you want to put the mortar on. You'd think that the rough side would give better 'tooth' for the mortar, but it's designed to be used smooth side up. Get a couple of tubes of liquid nails or equivalent to bond the Durock to the underlayment, in addition to the screws or nails you are going to use.
Scott
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Scott Cramer wrote:

Just completed 600 Sqft of ceramic tile in the basement, and was told by a ceramic tile installer with 15 yrs of exp that you should always put mortar under the Durock. Same stuff as you're going to put the tile down with. Takes a little longer and you want to trowel it the same as settting tile, but hard as a rock when done. You want NO flex in the floor when done. Liquid nails will not help this situation. As to the side up, I think it says so on the label, at least it did on mine that I purchased at HD.
And if you have a framing nailer, get a box of ring shank nails and angle them when setting them. I did this and it saved me TONS of time. It took 15 minutes to screw 1 panel in place and I could nail it in less than 5. Floor is rock solid, no cracks in the grout anywhere, and we've had several parties with 20-30 people on it at a time with no detriment to the floor.
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I put thinset under the durock when using it on a countertop. the first counter I did I got the thinset to thick so it created low spots wherever I sank a screw as it squished the stuff down near the screw but couldn't compact the thinset further away. the next time I did a countertop I made the thinset a bit more wet and troweled on a slightly thinner layer. Came out perfecto! My mentor, Michael Byrne suggests the thinset under Durock. Whatever he says, I pretty much follow...except he uses nails.
dave
Creamy Goodness wrote:

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of
and
i'd probably put it rough side up to provide additional tooth for the thinset.
regards, charlie cave creek, az
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the rough side is for mortar and the smooth side is used with mastics. that's the official word on their website... you might download their pdf file on using the stuff.
dave
Jon B. wrote:

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On 28 Oct 2003, Bay Area Dave spake unto rec.woodworking:

    If Durock PDF says rough side up, I stand corrected. The brand I used was Hardibacker, and it specified smooth side up for all applications.
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Well thank you very much for your quick responses. I'll install it to the particle board smooth side down with mortar and flat screws this afternoon.
I knew I came to the right place!
Thanks again, Jon

applications.
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I think you should check with your building inspector. To the best of my knowledge (and I've used wood stoves to heat my houses for 23 years) a woodstove set on ceramic tiles over 1/4 inch of Durock over particle board does not meet the building code anywhere, will not pass inspection, and is a fire waiting to happen. If you have a fire that is caused by such an unsafe installation, your insurance company is unlikely to pay any claim you may have to make.
Someone else spoke of using mastic to fasten the tiles to the Durock. If the mastic is a flammable material, this would be even more unsafe.
Don
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Don,
Thanks for the concern. You realize of course that the particle board and Durock are simply foundation materials and will be completely enclosed by the non-combustible tile right?
Here's a link to the stove:
http://www.avalonstoves.com/product.asp?dept_id=4&sku4
As you can see it's a free-standing unit with the fire box positioned almost a foot and a half above the tile. The pad I'm building meets Travis Industries specifications for wall and floor clearances. Basically, I'm building an exact replica of what TI provides to its dealers so there shouldn't be a problem. However, thanks...
Jon

sheet of

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Jon B. wrote:

Jon,
One other thing, don't use the premixed mastic! I used it on a smaller job in my master bath and it didn't work at all! Do a google search, but I found (after laying the most important tiles in the angled design) most people had no luck using a pre-mixed mastic. It essentially never dried and you end up with tiles that rock and break the grout.
Use a mortar based thinset and mix it properly. I used a wheelbarrow and a hoe to mix mine. Worked great and I'll never use the pre-mix again.
Mike
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job
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mastic is for walls. thinset for floors. damhikt.
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Thanks Mike. I used UltraFlex 2 mortar...very solid. Today I start laying the tile. So far so good...
Jon

job
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Jon:
I realize what you intend to do, but I still think your reasoning is wrong. I strongly suggest that you consult the building inspector. I don't think that he will agree with you. If the particle board gets hot enough, it can start to burn on the opposite side where it is not covered with a non-flammable material. From what I've read on the matter, wood that is repeatedly exposed to temperatures as low as the boiling point of water will eventually burn when exposed to such low temperatures (it may take years to happen). If what you propose to do is OK, then why worry about having the inspector see it. Your insurance company is not likely be happy about an uninspected installation, and not only your house but also your life is at risk.
Don
Don

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Donald,
Typically the manufacturer describes wall and floor clearances for their equipment. These may be on the order of a foot or two. How is particle board covered with a layer of durock and tile substantially different than wooden studs covered in gyp-board which are acceptable as wall covering?
The tile is there to prevent embers or anything that falls out of the stove from landing on the floor and starting a fire.
It sounds to me that you are suggesting that the manufacturers own specifications are not nearly stringent enough. It sounds to me that you might be wrong.
-Jack

smooth
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Donald Cranstone wrote:

This is another one of those items that just because you don't get bit today doesn't mean you won't get bit tomorrow.
I have a similar problem. I have a small commercial range:
http://stangii.com/range/imp.JPG
In the picture the range is roughly centered in it's alcove.
The installation manual says 4" clearance for the back and 6" on the sides for combustible and 0" for noncombustible. As you can se in the graphic I have sufficient clearance for sides and back (what can't be seen is the walls and ceiling are 5/8 fire code, the ceiling has two layers)
The manual says nothing about the bottom.
Plans are to build wood frame second walls covered with "backboard"* and the board covered with tiles.
Enough about me, on to the topic.
*The Backboard:
In my materials class (Kent State) I learnt ceramics are refractory. Heat penetrates a ceramic and is refracted (bent) back towards the surface. The greater the heat the deeper the heat penetrates, the greater the apparent temperature on the cool side. I guess you could look at ceramics as being heat reflectors as that's the apparent action, but that's not the actual mechanism of what's happening.
Cement is a ceramic.( So I guess cement board is too ) It needs a thickness in order to be able to work.
A property of ceramics is the finer the grain and denser the item the better it's refracting properties.
That is why a porcelain tile is better than that red stuff at HD/L for ? $1, $2 a foot?
That is why you need to get the best tile you can afford. Unless your paying for factors other than the quality of ceramic (decoration, glazing, getting ripped off) the more expensive the tile the better refractor it makes.
Back to me:
I was working in a factory making grinders. Sometimes we would line the equipment with aluminum oxide tiles about an inch thick. I don't think I got quite enough.
Back to sub:
Backboard, In my class I learnt of a relatively new (post asbestos) materials called Kaowool HS board. It's a ceramic board designed as a refractory that can be cement coated and has structural properties. The guy I was in class with (Bob) works for a firm that installs refractory materials (furnace rebuilding). He said the price wasn't that bad but that's relative to the other materials he worked with. Online I heard it was pricey. ??
I'm going to research Kaowool a bit more and if it has properties suitable to being used as a backboard or underlayment, and meets the price restrictions, I'll go that route.
Otherwise I'll probably do 3/4 inches of cement board with a good quality tile. I don't care if the floor ends up 1 1/2" or more thick. I don't like the thought but I would rather have a platform than a house fire.
--
Mark

N.E. Ohio
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Mark,
Personally I think you are being a bit paranoid. You already have 4 inches of clearance below your stove due to the legs. In addition, heat generally travels up. A layer of tin foil would suffice to protect your floor. Just make sure you install it on your head.
-Jack

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radiant heat travels in any direction, Jack.
you are confusing heated AIR which travels upwards, as opposed to radiated heat for a hot, solid object.
dave
JackD wrote:

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1) There are several layers of stainless steel and insulation between the flame at the top of the stove and the underside of the stove. The bottom of the stove will radiate MUCH less heat than the raw flame will. Do you cover your cabinets in gypboard?
2) Even the oven won't radiate that much heat or you would burn yourself while stirring your oatmeal. A toaster oven gets hot as a real oven, yet they sit on laminate over particle board all day long.
3) How many built-in ovens have you seen? Do you realize that they are being installed with zero clearance on the bottom of the oven in wooden cabinetry every day? The Horror!
Kitchen fires are mostly caused by burning grease, not by the thermal radiation emitted by hot ovens. There is a reason that there is no clearance mentioned for the bottom of the stove. Reason is THERE IS ALREADY ENOUGH CLEARANCE. Duh.
Put on your foil hats and be on your way.
-Jack

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I agree with you regarding ovens and installation. I was merely pointing out the GENERAL concept of radiant versus convection heat. (Will skip conduction) You had originally posted that heat general travels upwards. Perhaps you meant specifically in an oven installation, for the purposes of being safe and following applicable codes. I agree with that, 100%!
dave
JackD wrote:

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