adhesive (thinset) only rated to 120 degrees for Hearth

[beanbone]

Hi -

I've rebuilt my hearth once because of sizing problems, so I'm hoping I won't have to do it again:

I just laid down all the proper materials (micor board, terra cotta pavers etc.) to achieve a high R-value for my hearth. But, after building the hearth, I realized that the adhesive I used is only rated to 120 degrees. Is this going to be a problem?

Thanks for your help.

 

[jtp10181]

What kind of adhesive is it? Brand / Model would be nice to know.

 

[ChipTam]

I don't think you'll have a problem. I used thinset to adhere the tiles for my hearth and I haven't had any problem. I can actually hold my hand on the hearth beneath the stove with a roaring fire going so the hearth doesn't get very hot and I suspect the R-value requirements for a hearth are written by the manufacturer's legal department.

ChipTam

 

[edthedawg]

pls advise the exact type of "adhesive" (says 'thinset' but there are varying types). also let us know the stove you plan to put on it? my Heritage can easily heat the hearth tiles to 170+ in areas.

that being said, you probably still don't have a huge problem, so long as you actually used a mortar/thinset and not a mastic-type adhesive.

 

[beanbone]

Hi Pyro -

Not sure of the brand... I think it's just poly-modified. I'm wondering if the worst that'll happen is the glue will come dislodged

 

[webbie]

I think it will take higher temps than that.....that may be continuous service in semi-structural or structural situations.

Note, here is a wiki article and some text copied from it:
https://www.hearth.com/econtent/index.php/wiki/Adhesives_for_the_Hearth/

4. Thinsets, epoxy, grouts and mortars – are usually used in lower temperature (under 200 degrees F) applications, such as stove hearths (the floors below a stove), rear wall protection and fireplace facades. In many of these cases, the surface temperature is unlikely to reach above 130, and most products can take that kind of low-level heat. However, if your application is likely to get much warmer than that, please read the label of the product you intend to use. Example: epoxy tile cement can be rated for service at 160 degrees F , while some premix thinsets are only 120 F.

FYI, I doubt even regular mortar comes with a very high temp. rating. Neither does tile itself.

All in all, I don't think you will have a problem with normal stoves with air spaces underneath them.

 

[beanbone]

Fire Honor -

This is what I was afraid of... I just bought a hearthstone heritage. My tiles are 1/2 terra cotta. Do you think that would help with insulation a bit?

 

[edthedawg]

If you used something like Versabond or Flexbond mortar (routinely available thinset mortars available from a place like Home Depot), you'll be fine. The tile doesn't offer any "insulation". Worst case is you may wind up with some loose tiles over time, but it sounds like we have nearly identical setups - and similar to vast quantities of other individuals on this site - so you'll be fine.

Post some photos of the build!!

 

[beanbone]

will do... I just phoned the company, -- Invision-Tech -- they said at the worst, the tiles would come loose. Thanks for advice!

 

[begreen]

I think that might be Tec Invision? If so, although it is not recommended for warm applications, at least the product is non-flammable. It appears to be an acrylic latex adhesive. http://tecinvision.com/product_adhesive.cfm

 

[edthedawg]

I was a little concerned we hadn't heard the word "mortar" from the OP on this one... if this is the type of product being used (http://tecinvision.com/product_adhesive.cfm), then it almost certainly counter-indicated for this application. Not dangerous - just not something you SHOULD use.

 

[breathebeast]

Tagging onto this, because I'm having the same concerns. I have Pro Flex Select thinset with TEC acrylic grout additive. The additive doesn't say anything about heat, and it seems that a lot of people have used acrytlic additive in the thinset at their hearths. But the thinset itself says use at up to 95 degrees! I'm hoping that's for setting the thinset in place...it is a latex-modified thinset. And, I probably shouldn't be even on here asking, because the lady at the tile place called the company to make sure it was okay, and finally got through to someone who gave her the okay, said it was fine. Guess it's just a bit confusing to me, to see the one temperature listed on the bag, and yet the company saying it's fine.