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-   -   Slate Questions (https://www.johnbridge.com/vbulletin/showthread.php?t=63803)

cgarai 06-18-2008 01:20 AM

Slate Questions
 
Hi,

My name is Chris and I'm new to the board. I have a couple of questions regarding slate tile.

1. I like the look of slate tile with no grout. I know several here don't recommend it and I can see some of the problems: debris collection, more pronounced lips and possible gaps due to the tiles not being precisely the same size. Assuming I am willing to accept those faults (characteristics), are there other reasons that it would be a bad idea or cause the job to fail?

2. A Schluter rep told me that slate has a high thermal coef. of expansion and that a minimum grout line of 1/8" is required to help absorb this expansion. I didn't think that grout had any elastic properties? We were discussing slate in an exterior installation over occupied space that gets sun for several hours a day. In the exterior installation I'm not as interested in going with a groutless installation as it seems that frost could reek havoc. (I'm in CA north of SF, so real freezing is rare, but not unheard of.)

Here are the various conditions for this job:

1. Quartzite over Ditra, over SLC, over slab w/radiant heat (hot water).

2. Slate over Ditra, over mortar bed with radiant, over plywood and 14" TJI in bathrooms.

3. Slate on exterior decks. All are elevated, one is over occupied space. Using Ditra over mortar bed, over Troba, over double layer of bituminous membrane over plywood and framing.

Thanks,

Chris

Brad Denny 06-18-2008 05:06 AM

Hello and Welcome Chris!
If you can't be persuaded by a Schluter rep, it's doubtful we're going to have much effect...those guys are usually well informed. You could think of it this way...

You are going to install the slate tile into a bed of thinset, yes? You trowel on the mortar and press the tile into the thinset, DISPLACING the thinset to achieve full coverage. Gotta have full coverage cause slate is soft. The thinset has to go somewhere, and usually it oozes some into the joint where it has space to pass the bottom edge of the tile (essentially being cradled by mortar). I don't think you can install slate without some type of joint and grout, without compromising the integrity of the install. Besides, they don't put a micrometer to each piece as it leaves the place of fabrication, butting 20 pieces together you'd have to have a larger space somewhere that would be in need of grout.

Aside from that, it sounds like you have been well informed. Do you have specific questions for the assembly of your floors?
:)

DJ Hostetler 06-23-2008 08:34 PM

Slate grout
 
Hello, I have slate tile questions too!!! my name is Diane.
I am installing slate tile on the floor in a three season porch (Northern Ohio seasons). With the extremes in temperature are there any installation problems? Like minimum grout line (the previous poster was told 1/8"). Should I use sanded or unsanded grout? I am going to use Homax Pro Sealer (recommended by Lowe's) before I grout. Can i use another type of finisher/sealer after I apply the sealer to get more of a sheen?

Brad Denny 06-23-2008 09:00 PM

Hi Diane,
You'll likely want (or a moderator will do so for you) to have your own thread as you might get overlooked in this one. ;)
As mentioned above, slate usually drastically ranges in size, so you'd be better off having no less than 1/8", but usually you can lay out eight or so in a row with a joint that looks good to you and get an average layout for two tiles. Slate does absorb quite a bit, so sealer for exterior is absolutely necessary. Try to stay away from the shiniest of sealers, as they could make it slick when wet. Try reading up on AquaMix's options for slate. You'll may need to call their technical people to ask about compatibility with the Homax stuff. You definitely want to use sanded grout, and a grout release or presealing would make clean up much easier. When installing outdoors 100% coverage is key. :)


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