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Surfrunner 11-29-2012 01:39 PM

Granite slab installation
Can I use thinset to lay a granite slab to hardiboard for a fireplace hearth ? need to level it off bec there is a 1/8" gap
between the hardiboard and the bamboo floor. The hadiboard is going to be liquidnailed to the concrete slab. Its Uba Tuba dark granite if that matters


Tscarborough 11-29-2012 01:43 PM

Yes, that is what it is for.

stadry 11-29-2012 03:17 PM

who sez you need hardibacker - how thick is the slab ? when i did ours, i just laid it in a floor cutout,,, it was 4" thick & too heavy to bring down the stairs safely by myself so i cut it into 4pcs,,, IF yours is only 1" - 1.5", thinset will work fine IF you level the slabette :laughing:

Surfrunner 11-29-2012 06:34 PM

Granite slab
Ok folks thanks for the replies !!
Let me explain further.. I had an old slate hearth appx 48" x 19".
and we had bamboo floors installed around it.

Fast forward to now. I removed the old slate and I picked up a granite slab 60x 20 which is going over the old opening (hole) which is 48 x 19" x appx 3/8- 1/2"deep and the floor is not level and the granite slab is going to overlap a few inches on each side and sit on the bamboo. SO you are telling me forget the backer board and just use thin set to level the floor and set the granite. correct ?

Thanks again!

Surfrunner 11-29-2012 06:36 PM

granite slab
Oops forget the granite is 3/4" thick.

oh'mike 11-29-2012 07:37 PM

Not a great plan----the granite needs a masonry base---no wood under it at all----wood moves--expands and contracts==

I suggest that you cut out the bamboo that is going to be under the slab so the base can be built up without worry ----

Tscarborough 11-29-2012 07:38 PM

3/8-1/2 is too much for thinset, use the backer.

stadry 11-30-2012 04:49 AM

having enough information is a help when advising methods/mtls :yes:

Surfrunner 12-01-2012 05:54 AM

Granite Installation
Thanks again for the replies, much appreciated !! :thumbup:

stadry 12-01-2012 06:41 AM

that piece weighs approx 1,160# making this task more than slightly difficult/involved,,, i think IF i'd wanted to tackle it, i'd have laid the piece directly on the conc floor using 1/8" spacers every 8" o/c both directions AFTER being certain the floor was level,,, then i'd have placed dabs of silicone sealant ( you might call it caulk ) in between the spacers,,, we would've used teflon as that's what we had on the truck when installing cemetery monuments,,, before teflon came on the scent, we used pennies ( fairly uniform in height ),,, i'd also not be surprised to find the piece cracks eventually as granite has slight flexibility - about the same as glass ( float or tempered ),,, hope for the best & don't skimp ! :no:

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