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Tiling our deck in extreme climate conditions

1280 Views 3 Replies 4 Participants Last post by  Bud Cline
My husband and I are trying to plan our deck. We are trying to do our research to find the best way to do what we want to do. We live in Saskatchewan, Canada. We have hot summers and very cold winters. We want to tile our deck, and we know what we want to do, but we want to do it in the best way, while being as inexpensive as possible.

We know that we want to use porcelain tile, (we have found a great 24x24 tile, that looks and feels very much like slate.) The plan is to put the tile inside a cedar trim on our outdoor deck 12' in the air. We understand that the joists need to be closely centered in order to have a structure that doesn't move a lot. So we're good with the actual structure. We just aren't sure how to lay the tile. Here are the options we've considered:

1. Putting down 2 layers of 5/8 inch plywood. Using a waterproof roll on "paint" (for lack of a better word) Over which we'd put down Schluter Ditra, and then the tiles.

2. Again using 2 layers of 5/8 plywood, Using the roll on water proofing, over which we would set the tiles using kerabond and keralastic.

We are having a hard time finding out exactly which would be best for our scenario, so we'd love your input. Thanks!
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Just wondering why are you using 2 layers of plywood?
I don't want to rain on your parade, you have an interesting idea that frankly I have never seen done (tile on an outdoor deck). However, consider a few things before you go ahead.

Porcelain tile in 24 inch format is considered large format tile. Tile is brittle, and in large format it is more subject to cracking due to load. For such a large format tile, I believe the tile institute recommendation is a stiffness ratio of L720. Normal code deck loading is about 50 pounds per square foot, and you are unlikely to achieve L720 deflection criteria with any reasonable combination of beams and joists. You absolutely need to check the maximum deflection through analysis of your structure, and you are not going to be able to look this up in standard tables, since standard tables are only going to cover 20 psf (attic), 30 psf (bedroom), or 40 psf (kitchen) type loads, and a deck is beyond that loading.

Additionally, your deck is subject to exceptionally harsh temperature swings, which are going to result in unusual stresses on the tile. One of the tile guys here may be able to comment on the effect of 140 degree F temperature swings on tile and grout.

There may be a reason I have never seen a tiled deck, and it probably relates to deflection and temperature swings. But maybe one of our tile pros knows how to do it so you won't have any problems.
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What size are the joists?
What is the species?
What is their spacing?
What is the unsupported span of the joists?

There are products available for such an installation but the extremes you have may preclude the use of any system.

You saw fit to specify a thinset product in example #2 but you did not specify a thinset in example #1, why is that?:)
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