building my first hearth... Mortar?
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What is it? And how do you know durock wouldn't have had the same result given whatever conditions that material were under?
tradergordo said:
As best I can tell from the picture, the peice that is tilted up is the tile or whatever is being used for the floor treatment. The underlayment looks like some sort of cement board, covered with whatever adhesive was used to fasten down the tiles, can't tell if it's Durock brand or not. The discoloration (I'm not sure it's enough to rate being considered "charring") I wouldn't say is necessarily a problem with the cement board, as it could be a stain from the thinset or other material.
What I can say is that Durock is "UL LISTED for use with UL Listed solid fuel room heaters and fireplace stoves" and that Durock's data sheets specify the ANSI 118.4 or 118.1 standard for the mortar. When I was planning out my hearth extension, and doing some research for the Hearth Construction article in the WIKI, I spent considerable time on the phone calling the tech support lines for Durock, Hardibacker, Wonderboard, and Permabase. Durock was the ONLY one that said flat out that hearth pad construction was a reccomended application. Hardibacker said they were approved for making clearance reduction walls, but NOT for hearth pads, Wonderboard didn't really answer beyond saying that it shouldn't be exposed to more than 350*F, and Permabase said they were "not non-combustible"
When I asked for clarification on the mortar specs, Durock's tech support folks said that the standards basically translated to "Latex modified" thinset, and specifically suggested the Flexbond brand. (Which isn't one of their products BTW) I have subsequently heard from another poster that Versabond also meets the ANSI standards, however NONE of the "readymix in a bucket" products I've checked do. Both Flexbond and Versabond are dry powder products that get mixed with water at the time of use (like concrete) - the reason given for the use of the latex fortified mortar is that it is better able to handle the thermal cycling that a hearth undergoes.
BTW, my Encore cat (w/ required bottom and ash pan door heat shields) requires only a "non-combustible surface" such as '1/4" non-asbestos mineral board or 24g sheet metal' - Durock plus tile far exceeds this requirement.
What I've observed is that my raised brick hearth (that barely met the old NFPA spec as it turns out) gets hot enough to be on the edge of what is comfortable to stand on for any length of time. The 18" Durock and slate tile extension gets decidedly warm, but not uncomfortable.
Gooserider
tradergordo said:
Gordo,
I have some things to do before I answer your questions in detail... but please, tell us in the meanwhile if you used out-of-the-can mastic or did you use mortar based thinset on your new hearth?
Just curious,
Jim
Jim Walsh said:
Thinset. I don't even know what mastic is - haha. Every set of hearth building instructions I've read said to use thinset. My hearth consists of a layer of durock, a layer of micore 300, another layer of durock, and ceramic tiles on top.
![[Hearth.com] building my first hearth... Mortar?](/talk/proxy.php?image=http%3A%2F%2Fwww.gordosoft.com%2Fwoodstove%2Fmaliastove.jpg&hash=2199a4a16beea34a9ca857e39c9e4d6a "[Hearth.com] building my first hearth... Mortar?")
tradergordo said:Jim Walsh said:
Thinset. I don't even know what mastic is - haha. Every set of hearth building instructions I've read said to use thinset. My hearth consists of a layer of durock, a layer of micore 300, another layer of durock, and ceramic tiles on top.
Hey Gordo,
Nice stove and floor... but those curtains and wooden window/floor trim near rhe stove?....
Please tell us you modified that since you did the install.
We wouldn't want Bee, who wants good advice, to see that set up would we?
I'll take this as a personal attack. :coolmad:
But again, your suggestion as to use a mastic is NOT appropriate, and as per Bee's application with random ungauged slate it is NOT recommended by any means. :shut:
So your point is? :question:
But again, your suggestion as to use a mastic is NOT appropriate, and as per Bee's application with random ungauged slate it is NOT recommended by any means. :shut:
So your point is? :question:
My limited experience with hearth building, which we did exactly once two years ago, was as follows. As is typical, hubby sent me to Menards to buy the stuff we needed, because he doesn't like shopping. I REALLY wanted to buy the pre-mixed tile adhesive, since it came in much smaller containers, would be less messy (no dust), harder to screw up (if wrong amount of water added, etc.), easier to use (you don't need to worry about timing quite as much), plus it was cheaper. However, he had told me to buy some named kind of mortar and it wasn't called that. I spent lots of time on the cell phone with the tech support of the mortar/adhesive companies, after deciphering their numbers on the packages. Had to buy the latex modified thinset because the pre-mix stuff was not certified for hearth applications, had to do with heat tolerances over time. That is not to say there couldn't be some pre-mix tile adhesive that is okay, but Menards, a large DIY chain, didn't have any like that. I was bummed because the thinset mortar stuff that was appropriate and correctly rated for such an application only came in a 50 or 60 pound bag and I could hardly lift the darn thing in and out of the shopping cart and into our truck, it being an awkward shape and not having handles or anything. And it was messy and dusty and all those things, but that was the only choice I had at that time at that store. I'm not an expert by any means, but if you want some thinset mix we have plenty left. 
We had plywood, Micore 300, durock, and ceramic tile as our base, we needed an R value of 1. As others have said, the hearth itself doesn't get very warm, but it is true that occasional sparks and hot bits of wood visit it, so it needs to be able to handle heat.
We had plywood, Micore 300, durock, and ceramic tile as our base, we needed an R value of 1. As others have said, the hearth itself doesn't get very warm, but it is true that occasional sparks and hot bits of wood visit it, so it needs to be able to handle heat.
God I hope your hubby doesn't expect you to make pancakes in the morning? ;-P Mixing thinset is 'just add water'.. you don't have to add the eggs and oil. :red: :red: ;-)
Kathy and I worked on the project together, I could have sent her out and she would have picked up the 40# bag of thinset or batted her cute eyelashes and I am certain a masculine man would have loaded it into the van.
![[Hearth.com] building my first hearth... Mortar?](https://www.hearth.com/talk/attachments/imgp0225-webp.206973/ "[Hearth.com] building my first hearth... Mortar?")
As per cost?.... 40#s of thinset is about $10.00 US. For applying ~30sf and applying both the Durock and 13" lugged PEI-5 tile we still had some left. Show me an out-of-the-can product that will do that with a heavy lugged tile (btw.. mastics are NOT recommended for heavy lugged tile).
Kathy and I worked on the project together, I could have sent her out and she would have picked up the 40# bag of thinset or batted her cute eyelashes and I am certain a masculine man would have loaded it into the van.
As per cost?.... 40#s of thinset is about $10.00 US. For applying ~30sf and applying both the Durock and 13" lugged PEI-5 tile we still had some left. Show me an out-of-the-can product that will do that with a heavy lugged tile (btw.. mastics are NOT recommended for heavy lugged tile).
Jim Walsh said:
It meets all clearances to combustibles, and is up to code, thanks for the concern. Again these are the things people need to check in their owner's manuals and/or with the local fire department and building inspector, before installing a stove. As for the curtains, they were soaked in flame stop. I personally burned a sample of the curtain, pre and post treatment, with a propane torch, to see the effectiveness of the product for myself. Great non-toxic product, I highly recommend. They have demo videos on their website as well.
- Feb 5, 2006
- 400
In the tile business for a long time. Unsanded grout (or also called dry grout) should NOT be used for joints OVER 1/8 wide (someone mentioned using it for larger joints). It is not strong/durable enough. Maybe with the old wet grouts (look that one up) but those have not been used for about 20 years. Anything wider than 1/8 inch should really get sanded grout (also known as joint filler).
Latex additives in the thinset and the grout do a few things: INCREASE bond strength, reduce porousity, and allow for slightly more flexion over a span. They do have some built in meldewcides and help retain color. There are a few new additives on the market that do the same thing as the latex modifiers, but are not latex. Jury still out on them. Not even sure about heat applications.
As far as using mastics (most mastics are an organic based adhesive) to bond tile with. Anything over 4x4 inch will take forever to cure out. It requires solvent evaporation for the stuff to "dry". Any tiles larger than that takes along time, especially glazed tiles. No place for the solvents to go except in the joints ( no adsoprtion/vapour transmission. I personally would not want to use this type of adhesive in an area that receives heat, but, if it has the specs and says it's OK, then no blood, no foul. I have used heat many times to remove tiles that have been installed using mastics. The thinsets are just so much more stable and add strength to the entire job. I feel the thinset is better for this type of application. I am also actually surpized that the latex additives in the thinset are not an issue with heat, but all these products have been tested, so if the specs say it's ok, then it's OK. KD
Latex additives in the thinset and the grout do a few things: INCREASE bond strength, reduce porousity, and allow for slightly more flexion over a span. They do have some built in meldewcides and help retain color. There are a few new additives on the market that do the same thing as the latex modifiers, but are not latex. Jury still out on them. Not even sure about heat applications.
As far as using mastics (most mastics are an organic based adhesive) to bond tile with. Anything over 4x4 inch will take forever to cure out. It requires solvent evaporation for the stuff to "dry". Any tiles larger than that takes along time, especially glazed tiles. No place for the solvents to go except in the joints ( no adsoprtion/vapour transmission. I personally would not want to use this type of adhesive in an area that receives heat, but, if it has the specs and says it's OK, then no blood, no foul. I have used heat many times to remove tiles that have been installed using mastics. The thinsets are just so much more stable and add strength to the entire job. I feel the thinset is better for this type of application. I am also actually surpized that the latex additives in the thinset are not an issue with heat, but all these products have been tested, so if the specs say it's ok, then it's OK. KD
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