Thread: Slate Questions
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Unread 06-18-2008, 01:20 AM   #1
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Join Date: Jan 2007
Posts: 2
Slate Questions


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.


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