# Wood deck subfloor for tile?



## TaskBoy (Sep 18, 2008)

UPDATE:
My idea of tiling our deck got killed by City Planning today as they said they wanted it engineered. Well, I don't have time or money for that now. I can always tile later  

So, I need a walkable, waterproof coating. The subfloor/floor is going to be 1.25 T and G ply in case we decide to tile down the road. It will be sloped 1-inch for every 12 feet. The deck size is 14 x 20 and is over a garage (occupied space). We're in So. Cal. so it is not as wet or humid as other parts of the country may be but we do get a few heavy rains during the winter. There will be no freezing where we are. Thanks.

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I need to know the recommended amount of ext. ply  for a 14 x 20 exterior deck over occupied space (enclosed garage/workshop). I plan to tile over the deck. The joists are double 2 x 8s, 16 inch centers running parallel with the 14 foot dimension. My moisture barrier will be Redgard by Custom Building products. So, is one 3/4 ply enough with a 1/4 inch WonderBoard over? Or two 3/4s w/ or w/o the WonderBoard needed? Thanks.


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## glennjanie (Sep 18, 2008)

Hello TaskBoy:
I would use PL 400 glue and screws in 25/32" underlayment grade, tounge and groove (use the glue in the t & g also) OSB. You don't want to add any more weight than necessary on that span but the glued underlayment gives some amazing test results!
The underlayment grade takes the place of the wonderboard and is sanded smooth and made to a high density specification. I would still use the Redgard.
Glenn


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## mikemeier (Sep 19, 2008)

I would also try putting a thin wet coat of mortar between the wood deck and underlayment. this will help smooth out any difference in heights between the boards. If not then you could pop some tiles loose over a low spot on the deck


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## sutcac (Nov 2, 2008)

You may want to look at the Dex-O-Tex website for your waterproof covering.  They have systems that will be walkable and that can just be tiled over later.

www.dex-o-tex.com


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