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JohnNoobie
01-22-2005, 04:54 PM
Does thinset have a maximum temp?

Rather than move my wood stove further into my basement office, I want to leave it close to a wall and save the floorspace. But I therefore need to make the wall fireproof.

I'm going to put up metal studs and screw CBU onto that. Where I go from there is the question.

I know the tile can handle the temps, but can thinset? This wall will be 7" from a wood /coal burning stove. Are there any special considerations I have to take regarding expansion-contraction from the heat? Would the latex component of a modified thinset present a problem?

I plan on putting a metal heatshield about 1" off the wall with ceramic spacers to reduce heat somewhat, but it's still only 7" away from the back of a stove that can burn a coal fire at around 1000 degrees F.

Thanks for any help you can give this newbie questing for a basement office. :bow:

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Davestone
01-22-2005, 04:59 PM
According to what i've been told it's the sand in thinset that presents a heat problem, cause it melts, so i was told to use an unsanded,but the latex issue wasn't covered. I know porcelain soaks up heat and slowly releases it, and soapstone does the same.I would use an unsanded thinset and glazed ceramic floor type tile, myself. :)Oh' they also said i could use some carotex to cut heat absorption in the thinset.

doitright
01-22-2005, 05:11 PM
Hi John, Welcome! :)

Good question! I'm going to sit back on this one.

MHI
01-22-2005, 05:16 PM
The melting point of sand is 2606 degrees fahrenheit. :)

Davestone
01-22-2005, 05:19 PM
Tell that to Ruck Bro. brick co., all i know when i did a fireplace is what they told me. :bow: :)

coleywrx
01-22-2005, 05:27 PM
Tell that to Ruck Bro. brick co., all i know when i did a fireplace is what they told me. :bow: :)
You've heard of glass, right? :p

Davestone
01-22-2005, 05:34 PM
:crazy: It may not have been the melt factor, but i know they don't put sand in firebrick, just clay.Yeah' what is in glass? sand and potash or sumthin? :)

coleywrx
01-22-2005, 05:35 PM
:crazy: It may not have been the melt factor, but i know they don't put sand in firebrick, just clay.Yeah' what is in glass? sand and potash or sumthin? :)
You're the expert, I was just giving you grief. :crazy:

Davestone
01-22-2005, 05:40 PM
Hah! expert! :tongue: :D

Hamilton
01-22-2005, 07:57 PM
im curious to hear the technical answer to this dilema. i have seen
fire surrounds for wood burning stoves made of metal 2x4 studs coverd with cbu when i was younger
but havent seen or done any myself since i was a youngen.

JohnNoobie
01-23-2005, 07:43 AM
Should I just space the tile really wide (or use thin brick) and lay it onto a 1/4" layer of regular mortar? I may not be able to find all the max temp stats for thinset, but mortar should obviously handle the temps fine.

Davestone
01-23-2005, 07:52 AM
To be honest, i've tiled around many hot places fireplaces, pits and such, and i didn't do anything special, and haven't had any problems i know of. I would stick with the unsanded materials myself, like small joints and unsanded thinset and grout myself. I know a cement block won't stand up to heat, and they're mostly sand, and not fired.That's all i got. :)

cx
01-23-2005, 08:02 AM
Just a word of caution, John: You might wanna run whatever wall solution you come up with by your insurance agent for a reading. They get real picky about wood-burning stove and chimney installations.

The NFPA specs for the floor under the stoves is usually the most stringent, presumably because that's the area where the distance from conbustable surfaces can't be specified. They generally require some metal, a lotta masonary, and some air space.

The manufacturers of the stoves sometimes have specs for wall protection if you want to reduce the specified distances from vertical surfaces, too. Not likely for going as close as you're planning, though.

Sounds like you're on the right track, but you don't wanna get an opinion from your insurance adjuster after the fire. It's one of those times when permission really can be better than forgiveness. :)

My opinion; worth price charged.

MHI
01-23-2005, 08:12 AM
John,

There are special mortars and brick for the inside of the firebox itself, where it will be in direct contact with the flames. The special fire bricks have been "fired" longer in a kiln to make them impervious to moisture. When normal bricks get hot enough the moisture in them expands and causes them to flake apart. Ever throw a rock in a campfire? After a few minutes it will explode into pieces.

For doing a wall behind the stove, anything that is non-combustible is fine. I don't know of any special high-temp thinsets, but one thing is for sure- its not going to catch fire.

Heat rises, so most of the 1000 degrees is going up. Not sideways toward the wall.

Thinset is the best choice. If you were to use a mastic or liquid nails for example, it could soften from the heat. :)

cx
01-23-2005, 10:57 AM
Well, Matt, we're dealing with some significant radiant heat here. Maybe where y'all live you've got that trained to go only up, but hereabouts it goes any which direction it happens to be pointin'. Yep, sideways, too. :shades:

My opinion; worth price charged.

Davy
01-23-2005, 11:27 AM
I used a heat proof cement when I put stone on my fireplace. I used it on the inside of the firebox where the face stone hung over the firebox opening. I put a thick layer on it to help tie everything together. It was really sticky and I wonder if it would bond tile. It is called "Tex Bond" and comes in small buckets, about 1 gallon or so. A stone mason I know uses it to bond fire brick together in the firebox instead of regular brick mortar. :)

doitright
01-23-2005, 11:41 AM
I think you're talking about refractory cement. Here's a link with some info - http://www.lmpl-india.com/prod_5.htm

JohnNoobie
01-23-2005, 03:44 PM
Just a word of caution, John: You might wanna run whatever wall solution you come up with by your insurance agent for a reading. They get real picky about wood-burning stove and chimney installations.

The NFPA specs for the floor under the stoves is usually the most stringent, presumably because that's the area where the distance from conbustable surfaces can't be specified. They generally require some metal, a lotta masonary, and some air space.


Excellent point. Forget insurance -- the stove is right under our master bedroom. :eek:

The insulated, double-wall stainless chimney and stove were installed by the previous owner. Concrete walls, concrete floor. No sign of heat problems with the flooring and joists above.

So what's the problem?

Well, prior to selling the house 4 month ago, they had a perimeter drain installed (nice), but it includes plastic flashing at the base of the wall. I can't light the stove because the plastic flashing will melt and burn. I could cut the flashing, but I don't want to hurt my 99 year warranty. :)

Since I need to protect the plastic, I thought I'd put up a fireproof wall. My stove mfg. specs are 30.5" of rear clearance to combustibles. That can be halved with a heat shield or a protected wall. It can be quartered with both. Taking the angle into effect, the stove will be about 13" away from the plastic flashing.

The CBU /metal stud wall (spaced 1" off the plastic) is considered a protected wall. I'm going to install a heat shield as well, spaced off the CBU wall by 1" ceramic spacers. In other words, I should be well within mfg. specs -- with about 5" to spare.

I was considering a latex-modified thinset as I thought it might withstand the expansion-contraction better, especially in the gap between CBU boards. But I was concerned about whether latex-modified thinset could stand the heat.

To be honest, I'm not sure how hot the surface of the wall will actually get. Especially with a steel heat shield as protection. As my username suggests, I am a newbie. However, I would like to do this right, especially since I am playing with fire. :rolleyes:

cx
01-23-2005, 10:56 PM
Another thing you might look into is high-temp stove caulk. Pretty non-standard thing to recommend in tile setting, but we use it to seal around flue sections and such alla time. Might be a fella could fix his tiles and grout with it, too - if he liked black grout, of course. :)

I would suggest you do an acutal test to see just how much heat you're gonna be dealing with there. A test that didn't involve burning down the house of burning that plastic thingee you're worried about.

I can't visualize the plastic drain thingee at all. Can you post us a picher? We like pichers. :D

My opinion; worth price charged.

bbcamp
01-24-2005, 06:07 AM
CX, it's like a plastic baseboard that's open in the back and is sealed to the wall and floor. It forms a gutter for channeling water from holes drilled at the bottom of the bottom course of blocks to a sump.

It's gonna need some sort of air gap between it and the non-combustible wall treatment to keep it cool, even at floor level.

cx
01-24-2005, 07:16 AM
Thanks, Bob. Ain't never heard tell of that there afore. :)

JohnNoobie
01-24-2005, 07:51 AM
I can't visualize the plastic drain thingee at all. Can you post us a picher? We like pichers. :D


Here's two pics. One is the stove, one is a closeup of the "plastic drain thingee" and it's relation to the basement wall and the new wall.

BTW, I was originally going to move the stove further into the room but decided that it would take up too much floor space. I could still move it a little, but since the protected wall + heat shield meets mfg. specs, I thought I'd try to figure a way to leave it where it is. I should have thought of that before framing with wood. :bang:

I plan on building a brick hearth under the furnace in place of the 4 concrete bricks that sit there now.

After 15 winters of use, there are no visible signs of any heat effect on the concrete wall, floor, or concrete bricks underneath -- so I imagine that standard cements will do just fine. In other words, any compounds that can stand the heat stresses that concrete can weather will suit me.

Thanks for the help everyone. I love this forum. :bow:

bbcamp
01-24-2005, 10:08 AM
Why not reframe the wall with steel studs?

JohnNoobie
01-24-2005, 10:22 AM
Why not reframe the wall with steel studs?

Yup, steel studs with CBU is my plan.

I'm just wondering if thinset, especially latex-modified thinset, can be put on the CBU and withstand the heat. I could just leave the CBU bare, but I thought it might look a bit nicer if I tiled or thin-bricked it. And even if the thinset can stand the heat, I'm wondering if it's liable to crack due to expansion-contraction -- especially between the CBU panels. Which is why I'm especially curious about latex-modified thinset.

Maybe I'll put in a word to customer support with a few mfg's. I thought I'd come here first because of three mfg's that I've contacted during this basement remodel, not one has gotten back to me. :tongue:

Also, the stove is due for a little paint, but other than that, appears to be in great shape. Even the platinum catalyst (for more efficient wood burning) appears to be fairly new, which is nice since it's a couple of hundred $$ to replace. My home doesn't *need* the extra heat, but I like the rustic feel and the money it could save me on my winter heating bills. In fact, I've got a whole hickory tree worth of wood seasoning in my back yard right now. Plus 450 lbs. of coal the previoius owners left behind.

Anyway, I'm starting to lean toward fireplace mortar and thin brick.

Chris the Rep
01-24-2005, 04:29 PM
US Gypsum, makers of Durock, have a system for using their material as a heatshield. Essentially, your existing frame wall is covered with gypsum board, then furred out and Durock attached to the furring strips. Then tile is attached to the Durock. The dead air space between the panels acts as an additional insulator. If applied as detailed, I wouldn't be too concerned about the drainage trough.

I wouldn't worry about thin-set myself, it's used to set tile under process vessels, commercial ovens, and wood burning stoves all of the time. If you can get the surface hot enough to have an effect on the small amount of latex in the mortar, you're probably going to have a chimney fire by then. But I wouldn't try to cheat the recommendations about clearances either; I'd err on the side of caution.

You're not planning to use this as a forge are you?

And I would check out what the insurance company says...I can have a wood or coal burning stove on my main living level, but not in my basement because of egress issues.

Chris

http://literature.usg.com/pdf/CB237.pdf

JohnNoobie
01-24-2005, 07:37 PM
Thanks, Chris!

Reading your link led to this doc, I found this, which is specifically about fire shields for solid fuel stoves:

http://literature.usg.com/pdf/CB198.pdf

They say using Durock this way reduces clearances by 2/3, which is better than the 1/2 my stove mfg. lists for a generic "protected wall." In any case, these are the most specific instructions I've seen for building such a wall. :yipee:

Regarding egress issues, my home inspector and the insurance company's inspector didn't have any issues with the stove when I bought the home 4 months ago. The pipe has a heat shield above it where it exits the basement (presumably to protect the 1st floor and joists). On the outside, it is met immediately by a double-walled stainless steel chimney that was professionally installed.

I'm hearing everyone when they say I should still talk to my insurance company, but my thinking is this -- they already inspected the site, and as long as I don't put anything combustible near the stove, I'm only making it safer. I haven't touched the stove itself. I plan to have a professional wood stove guy come over and check the stove out before I fire it up the first time -- after I finish everything.

I can see how if I touch, move or modify the stove or install combustibles -- I should talk to my insurance. But as it is, they already inspected it and I'm not touching what they inspected and approved. All I'm doing is making it even safer:

1) Installation of a fireproof wall (which I can now make to Durock's specs, thanks to you)
2) Metal heatshield mounted to the wall by 1" ceramic spacers (installed to the DutchWest stove mfg. specs)

Maybe I should talk to them, but I just hate asking anyone for permission to do anything -- especially when I believe they've already had their chance to complain.

Am I being stupid?

Also, I have a fear that calling my insurance company would get me involved with building inspectors and permits. My house is a cottage /bungalow with tons of stuff that's ok, but definitely not to code. I'm terrified that if I get a building inspector into my basement and he sees I'm already set to "remodel," he'll make me bring everything to code. I live in Natick, Mass and friends have warned me how ridig our building inspector is. The costs for my "build an office in the basement project" could spiral out of control like rebuilding Iraq. :twitch:

JohnNoobie
01-24-2005, 07:54 PM
BTW Chris, one more thanks. CB194 from USG not only details *exactly* how to install the Durock, but it specifically mentions using latex-fortified portland cement mortar to level the joints. Their only caveat is that is has to meet ANSI spec 118.4 or 118.1.

That, I think, answers my original question that started this thread, the one about thinset and high temps. :)

By "latex-fortified portland cement mortar," I assume they mean thinset. From what others here have said, I assume they mean unsanded. In any case, I'll make sure to look for ANSI spec 118.4 or 118.1 when I look for materials.

I think I now know enough to really get myself into some trouble. :crazy: My brother-in-law is coming for a visit this weekend. He's more of a weekend warrior than a newbie like me. Anyway, he promised me a day's work and now I know what to do with him.

MHI
01-24-2005, 07:57 PM
John,

If you ask your insurance company questions regarding the stove, they aren't going to send the permit police over to your house. The two have nothing to do with each other.

In my experience when asking both the fire chief and insurance about fireplaces and stoves, I have been told to just follow the manufacturers instructions.

If it were a new stove you were putting in, it would be a good idea to get a permit and have it inspected by the town.

Around here, nobody from the insurance company ever inspects houses. They might send someone out if you have a claim, but they mostly go by police and fire reports as proof. :)

Chris the Rep
01-24-2005, 08:35 PM
I understand about not wanting to have costs run out of control, nor do I like the idea of nosy people looking to line their pockets, or the pockets of the local governing authority, unnecessarily.

I only mentioned the egress point(s) because they were brought to my attention more as a fire safety issue. My agent told me that they don't like finished living space having only one entry/exit point. (I have typical 12" x 18" basement windows, which are not large enough to qualify as points of egress.) Their thinking is that since you're planning to install a stove, it must be there to keep you warm while in the room, so it's finished living space, and therefore requires a second point of egress. In this instance, I don't necessarily agree with it, but I understand it. It's not like it were a bedroom.

These people must lie awake at night dreaming of perils and how to either exclude them from coverages, or how to charge you and I an arm and a leg for them.

Chris

Chris the Rep
01-24-2005, 08:43 PM
ANSI 118.1 is an standard for unmodified (no latex) thin-set mortar, ANSI 118.4 is the standard for latex modified thin-set mortar. For your installation, I'd use a latex modified, that should handle almost any installation that you're considering.

Good luck

Chris

JohnNoobie
01-24-2005, 10:15 PM
I only mentioned the egress point(s) because they were brought to my attention more as a fire safety issue. My agent told me that they don't like finished living space having only one entry/exit point.

Oh, *my* egress. I thought you were talking about the smoke's egress.

I never thought about that. I guess that's what building inspectors are for. :rolleyes:

It would be kind of fun to build a secret exit door under my desk on the other side of my office. I'll install a secret stash right next to it - with a loaded firearm, fake id, and $500 in small bills. :idea:

Thanks everyone. If and when I ever get this job done, I'll try to upload some pics.