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?
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.
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.
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.
Creamy Goodness wrote:
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!
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.
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:
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...
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.
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.
Typically the manufacturer describes wall and floor clearances for their
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
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.
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:
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.
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.
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.
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.
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%!
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