Ceramic over PT deck


Old 07-11-03, 09:24 AM
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Question Ceramic over PT deck

Have an elevated PT deck about 12 months old. We did a DIY roof on the underside with corrugated vinyl sheets to keep the patio dry. We are getting leaks along the joints almost every time we have a heavy rain. I keep caulking and it keeps leaking.

To avoid having a caulk gun in my hand every 5 minutes, we are thinking of laying ceramic tile over the deck to effectively stop the leaks underneath. We are considering doing it by laying roofing paper then 1/2" PT ply sheets screwed to the deck then ceramic on top of that.

I'm not too sure that this is a workable solution although it sounds ok in principle. I guess my main concern is expansion and contraction of the deck and what that might do to my PT ply "sub floor" and the tile.

Does anyone have any comments or other ideas?

Cheers !
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Old 07-11-03, 08:21 PM
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Not knowing where you live, your proposal may be dueable if you were to do tile in a "mortar base" application. Please look at this in the concept of laying down your plywood and then going over the top with a rubber liner or EPDM roofing membrane. Like this for an idea...


The reason I suggest a EPDM roofing type material is that ceramic tile and grout is porous. You would have water coming through and obviously, your plywood, regardless of being treated would eventually fail and then you do it all over again! I have concern that we are increasing the total load and this would be a concern based upon what you may have now.

What you are proposing would not be my choice...look at these..it is similar to other under-deck roofings... better idea all the way around...



At least you have the option at any time to change decking, especially if you like the wood look and most do. I realize that there is expense, but for what little it will cost you over the above idea versus the time and money doing tile..the right way... you have the options to change the decking at anytime with no worry about cracked tiles, grout popping, etc. Any movement will cause damage above and this is going to happen once there is sufficient load on it if it was not framed to virtually have no movement and traditional deck construction does not provide this guarantee.

Just some thoughts!

Last edited by Doug Aleshire; 07-11-03 at 09:25 PM.
Old 07-11-03, 09:19 PM
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I agree with Doug, tiling really isn't a good solution in this case for many reasons.

I would look to put the rubber roof in place of the vinyl sheets if possible. You basically need a single piece to avoid problems down the road. The seams with the vinyl sheets are going to be a headache forever.

Maybe it would be easier to leave everything and work from the underside of the deck/above the patio? I've never used underdeck, but it's supposed to be a good product. Check it out at www.underdeck.com
Old 07-14-03, 07:50 AM
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Thanks Doug & Meffadawg

I live in MD. After our last winter (unusual) I also have some concerns about tile in the winter, particularly if they are somewhat porous.

We'll kick it around some more but it sounds to me like the best plan is to replace the vinyl sheet with something like you guys have recommended.

Old 07-14-03, 08:02 AM
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Another thought?

Instead of EPDM roofing membrane over ply (and tile over that?) could I use Weather Watch Ice and Water as used in roofing?

I don't know about the loads. I had someone else design and install the deck. I must admit after doing some research I'm not a great fan of adding a whole bunch more static load to the upper side.

Even though it would be a pain in the butt, I'm leaning toward the underside solution.
Old 07-14-03, 01:40 PM
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Another problem with tile is that it probably gets pretty darn hot in the sun.

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