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ixs0792 08-02-2007 08:32 AM

Outdoor tile on deck?
I am building a 16'x17' raised deck off of my living room in Western NY, and would like to have a tile surface (matches the old-world style of the stucco). I'm looking for suggestions and experience with tiles and sub-floors in freezing climates.

My current plan is to build the deck frame with 12" on center 2"x10" joists. Cover them with a pressure treated plywood sub-floor. Cover that with a standard concrete backerboard, outdoor thin set and then the porcelain tiles. Then go my best to seal the grout to prevent water from getting in.

My big concern if freezing and cracking. It looks like the Schluter-DITRA product may be a better choice instead of the backerboard. However the contractors I've talked to have no experience with this product. Is it a better solution?

Are there any other options that I should investigate?


JazMan 08-02-2007 11:56 PM


If you have to explain methods and products to the contractor, you're talking to the wrong contractor.

Your plans on how to build this deck for tile are wrong. First of all remember that the surface in the end must be sloped at least 1/4" per ft. for runoff. I like the idea of 2x10, you might even consider 2x12? Make sure you don't over span the joists, you'll need a mid-point support.

You do NOT want to use pressure treated plywood as the decking. Use 3/4" or thicker t&g subflooring plywood. It'll say something like 'exposure 1', the plies are laminated using exterior grade glues. Over the plywood you laminate cement backer board using the recommended thinset mortar and fastners etc. Finally install Ditra per Schluter's directions.

No doubt you'll have more questions, so lets hear them.


ixs0792 08-03-2007 08:13 PM

1 Attachment(s)
Okay, here is the rough sketch of my plan. I've already dug the four post holes so I would hate to fill in 4' deep holes and start chipping through the rock again.

Since the deck touches the house on two sides and I have the two beams I figured 2x10" on 12" centers joists should be more than enough.

I was skeptical that the standard pressure treated plywood would make good sub-flooring, thanks for the input. As for the backer board would you recommend 1/4" or 1/2"?

I've read some sites where people use the Schluter DITRA directly on top of the plywood. Does this work? It seems like you would need some sort of rigid support under the Ditra.

With that thought I've been debating going with 1/4" backer board and Ditra, or 1/2" backer board and a rubber membrane under the tile. Which do you think will be more likely to last for the next 20 years?


JazMan 08-03-2007 11:30 PM

I don't think that is going to be structurally good enough for tile. And only 4 posts? I think the main weakness is the two sides not attached to your house. Way too much overhang, very flimsy. The 3 short sides of the oct. will be very weak, especially the one on the lower right of the sketch. I'm guessing that deck would require about 9 posts if placed in the proper locations, maybe more because of the shape.

Ditra is installed over plywood for interior floors, but you must install an outdoor rated cement backer board for exterior. There are many more details for this type of installation. One is the installation of movement/ expansion joists around the perimeter AND in the field every 8-12 ft. in both directions of course.

I haven't found a 1/4" backer board I like for outdoor use. Durock makes a nice 5/16 and Permabase I think has a very good 3/8". Half inch is fine and may be easier to find?


ixs0792 08-04-2007 08:23 AM

About the post/load issue. Everywhere I read and people I talk to I say that 2x10" can span 16' when used at 1' centers for exterior decks. With this plan the maximum span (going with the span + 2 * the cantilever) is 12'. Looking through the Southern Pine span tables they rate 2x10" joists with a 20SPF dead load and a 60PSF live load 16+ feet. If I bump up the joists to 2x12" this would be >20' spans under the same loads.

To me this seems like it would be more than enough support for my family deck.

As for the backer board the only advantage with 1/4" over the 1/2" is the dead weight. The 1/2" costs minimally more and seems like a better idea.

So if I change the plan to 2x12" joists over the same four posts, 3/4" T&G "exposure 1" plywood, 1/2" backer board, ditra, and then the tiles. Do you think this would work?

Thanks for your help.


Barron911 01-31-2010 10:25 PM

Outdoor tile on deck
I would like to do the same and I saw on the show "Rock Solid" they used a product made for this and was the same as light weight concrete floor. It a metal corigated material and its a little smaller the the commercial stuff. Im going to try and find it.

poppameth 02-01-2010 05:53 AM

You still need a good starting structure though.

Barron911 02-01-2010 08:39 PM

Thanks you, just found this also. BB

RegeSullivan 02-02-2010 11:23 AM

I am not a tile guy but I can tell you with certainty that inch per foot will give you a 4 inch drop over 16 feet and it will be noticeable on a raised structure. Most paver manufacturers suggest 1/32 to 1/16 inch per foot so it seems to me per foot is not necessary. I think scaling back to 1/8 will still be overkill for your outdoor project but not noticeable enough to make it look and feel bad.


Bud Cline 02-02-2010 11:48 AM


I think you are looking at span tables that show minimums for live load/dead load characteristics but where is your criteria for deflection of same? Two by tens spanning sixteen feet may not meet the deflection requirements. Two by twelves spanning twenty feet may contain the same deflection issues.

If you are using ceramic tile your deflection cannot exceed 1/360, with stone tile 1/720.:)

I agree a 1/4" per foot slope isn't necessary in this case, that would show terribly. Typically the 1/4" slope is for shower receptor drainage and is a plumbing code thing for efficiently egressing liquids. A deck such as this with no raised lips on the edge to serve as dams wouldn't require much slope at all. Water will fall off the edges immediately. If anything I would slightly crown the center to assure against winter time pooling of water but beyond that - screw it.:)

The cantilever is however also a concern of mine. I think I would shorten that up some.:)

ChrisDIY 08-31-2010 09:40 AM

Any photos of finished deck?

tcesni 02-25-2012 06:49 PM

I used the TI Proboard corrugated system two years ago on a 500 sq ft raised deck and it has turned into a complete disaster. I used a slate tile, Starquartz acrylic grout and then sealed the deck. Water has penetrated the slate, the grout refused to cure (I re-grouted once) and this spring I am going to take off all the tile and start over. I would like to keep the TI Proboard in place and put something over the top because there are a billion screws in the Proboard. I am certainly open to suggestions.

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