Is slate tile suitable for exterior flooring in a colder climate?

Question

My brother-in-law lives in Northern Alberta, Canada, and is thinking about putting slate tiling down on the front deck. However, he's getting conflicting opinions, one place is saying that it will expand/contract too much in the cold climate, another is saying that it should be fine.

I've done some Internet searches and really haven't found much, but did run across one person saying that most of the problems are likely due to water incursion, so sealing it well and re-checking it every year should do the trick. There are also recommendations for "Ditra" or "Mapei" and then the thinset, and making sure there are no thinset voids behind the tiles.

Temperatures in the winter can get down to -20, so it is a bit chilly in the winter. The base is 3/8" plywood over waferboard on top of joists. There is a roof over it, but when it's snowy there will be some snow tracked onto it.

Answer 1

Is this a pressure treated deck on post and beams? Or on top of a foundation?

What ever you do, forget the waferboard and plywood. Use only pressure treated plywood.

Over time water will find its way under the tile and freeze and crack or separate the tiles. How long it lasts has to do with how well the tile and grout is sealed and how many voids you have under the tiles.

I did find a new solution. I haven't used it but it would be the only way i would install tile on a deck. It is a high strength fiberglass grate that installs on top of the joists. The tile is then glued on the grate. The grout lines are left open for water drainage.

http://www.gratedex.com/pg_moredetails/pg_moredetails.htm