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I have a detail in front of me for a deck over living space and I have concerns over its’ integrity. I know this topic has been done alot, but for good reason. Using a roof for outdoor living space is an efficient use of space and materials, has been done for centuries, looks great and just shouldn’t be so frightening. Anyway, here is what the approved specs call for from the bottom up, let your opinions fly…
*3/4″ cdx over 2x joists
*Thin-set acrylic mortar admix
*Glas-crete multiboard
*”Trowel & Seal” membrane
*Another layer of acrylic mortar admix
*”Polyblend” tile grout
*tile
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teo, couple of questions first.
Where? Drainage, scupper metal? tiled over or upto? It does sound scary, so many variables etc.
What is glas crete multiboard and is it structural, (similar to plywood)?
What is Trowel and seal membrane? Similar to roofing cement?
I'd be scared too!
I would certainly be concerned applying tile over wood in any application. If moisture gets under it....the game is over.
I would suggest that if you don't like the details and specifications that you have the architect sign you off of the warranty. Likely when you put it this way the architect may ask for your input, (if he is smart), and or take a good long look at his details.
L
*This is how I do it.2x joist no more than 16" O.C. Sized up a size if possible. T&G 3/4" ply decking. Sloped away from the buiding. A 1/4" fall in 10 feet will work fine as long as it is continous. You need to make sure your joist don't crown wrong a screw this up. Top it with Dura Deck.(816-421-5830) wich HAS to be installed by a dealer.
*teo, I think you are NUTS to install tile over this set-up,it WILL crack sooner or later, and with contractor luck it will be sooner rather than later, second grout is NOT waterproof and will allow water to penetrate to the substrates below, a good architect would never have designed this detail,which leads to my question, who designed this? was it an architect? or someone else? As an alternative do you have sufficient room to allow building a deck surface on the roof where you could then install the tile? or use regular decking materials? If I were you I'd definitly follow Larry's advice and have the designer sign you off from liability, IN WRITING, and have the owner sign off on that too, that may get their attention and help you change things, good luck, Geoff
*Are we talking about tile here, as in slippery when wet, as in fall down and scream LAW SUIT, or slide down the slope, do a half gainer over the railing, fall to the ground below and groan Law Suit???Just wonderin!-pm
*Click this Link for a better system
*Yeah, I'd built it, with everyone signing off that the this was the architect's idea, and would photograph every step of the way.Trowel and Seal is a shower pan type membrane in a bag. It works fine for showers. But showers don't have 15" of rain, aren't exposed to extreme temperatures, and don't have clowns tromping all over them. It may crack.I would have a rubber type sealant (EDPM) over one of the mortar based substrates, and another mortar based substrate over it. I would use natural flat rock suitable for outdoor use, sufficient rough to prevent slipping.I would slant the joists (or if they are level, the first layer of cdx as Rob suggested. If you can slant it right to left as well, so all the moister and water ends up in a single corner. Then put in a 4" floor drain, and pipe the deck water to the ground.I'd give the whole thing a 2 year warranty, and no more. I would expect 5-7 out of it, and you might get lucky and get 10-15.
*Odds are that this thing is gonna leak,and at the worst possible time.It will be leaking long before the rest of the roof is ready for replacement.When it does leak the homeowner is not going to care who signed what paper,who designed what,who waived who of liability.The only thing the homeowner will care about is that the roof leaks and he will be certain it is the roofers fault.Even if the roof leaks after the written warranty expires,the damage to your reputation could be huge.All the homewowner cares about is that he paid big bucks for this feature and a few years later it leaks like a sieve. He will take no reponsibility for his own poor judgement,blame you for everything,and slander your reputation to everyone he meets.The only reponsible thing for the contractor to do in this case is to say NO!Take controll of your own destiny and REFUSE to install a feature that we all know is doomed to an early failure.The few dollars you might make off this project will not be worth the grief headed your way.One of life's great pleasures is the power to say NO.Good Luck All,Stephen
*Dont know what your finished deck heigth (sp) is but could you have the membrane roofing installed, then build the deck so it spans across the thing without touching the roof?- maybe instead, build a 3 season porch up there, with a roof on top, and weather tight windows, then build a towering deck off the side of that.
*I'm adding up these reponses to a big fat NO! as I suspected. However, I was more optomistic to some modest form of modification of the idea being possible. Maybe that's why I have seen a few new tile decks but no old ones. I like the drainboard technology suggested by Jim. The Europeans have been building with tile for a bit longer and know some tricks. Also, Fred, how was installing a 400 sqft. seamless roof? That seems like a bit of a trick. Anyway, we'll research awhile longer and try to come to a consensus. All brilliant or otherwise ideas welcome. Thanks for the advice!