Want to put tile on my exterior deck. Have the epdm glued down on 5/8 t&g glued and screwed over 2×4 cross purlins at 1′ o/c attached to 9 1/2″ I Joists which are 16″ o/c. According to Ditra installation you need a drainage layer mat first and 1 1/2″ thick conc. base and then you put the ditra down and then tile. I have to ask do you need all of this. If ditra is impervious to water then what is the need for the drainage layer. Can you not do it any other way. If you need to go to all these layer why not just pour conc. base and then adhere the tile to the concrete and screw the extra exspense of the ditra. My deck has a 2% slope and is situated over the garage. The deck is 12’x13′.
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I'm just sayin'
Don't know, but you can try the johnbridge.com forum, they're the tile experts.
I saw a guy tile an exposed porch with just Hardieboard. I haven't been back to that job to see whether or not it worked out for him.
I mulled that idea over but worry about the freeze, thaw cycle if any movement would be more than the detra could handle. Don't feel like doing the tiles twice. My problem right now is if I do all that ditra recomends I won't meet code on the distance between top of deck and the door sill. Code is 3" min. between the two.
We did that (tile on two layers of Hardibacker glued to each other floating over Ameridrain and EPDM roofing and it's held up swell to the easy winters we get here in NC...------------------
"You cannot work hard enough to make up for a sloppy estimate."
No one can answer that, without a structuarl engineer getting involved ( for your saftey) try again later.
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The Ditra is placed in the system as an isolation membrane in this case. Any movement below in the wood or concrete should not transmit and crack your tiles. I have never used the product outside, but the principle should be the same.
>>If ditra is impervious to water then what is the need for the drainage layer.
Stuff happens
"Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive."
Howard Thurman
This strikes me as a very questionable idea. In addition to my doubts about the EPDM standing up to having a slab poured onto it (IMO thermal expansion/contraction will chafe through that rubber in short order), no roof membrane will last forever even under ideal conditions. And when it does start to leak there will be no way to patch the leak without expensive and invasive demolition.
I have tiled over flat roofs in the past, but did so using Blueskin and Durock under the Ditra. Yes, the same complaint about demolition being required to patch leaks applies, but the overall cost of the 'sandwich' is much lower than what you're proposing, and demolition is much less likely to do structural damage (if your slab has to go, you're gonna need to jackhammer it).
Finally, there is the weight factor. Are the roof joists on this garage rated to take an inch-and-a-half of concrete, plus tile and all the rest of it? That's a very big load; far beyond the standard load assumptions built into residential code tables. I'd suggest strongly that you get an engineer's upcheck on that before going any farther with this.
Dinosaur
How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....