I am designing a home in foothills of Northern California that will have a 12 1/2 ft wide by 45 ft long exposed solid deck over living space below. The surface of the deck is grouted Mexican Saltillo tile pavers and the deck will be surrounded by a capped stucco wall with properly placed drain scuppers. The supporting structure is TJI joists with a heavy plywood decking. My question is: What should be the buildup from the decking plywood upward to achieve a leakproof deck? Should a membrane be torched down or glued to the plywood and then followed with concrete. What type of membrane(EDPM rubber or plastic)? Should a 3 to 4″ layer of concrete with embedded 6 X 6, 10/10 welded wire reinforcement be used to form a bed for the tiles. Should the tiles be set in mud or a thinset? Should I be concerned about thermal expansion on this southeast facing exposure?
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I don't know if this will help, but we run into this 'deck over living space' problem quite a bit here in the islands. In fact, I am currently bidding a job where the roof of an apartment is the deck of the main house, and it leaks. What they have are 3"x6" joists/beams 24"OC, w/ 3/4" ply decking. Once that was all up, they treated the ply like we do roofs down here; primer, fill gaps and seams with an EPA-approved Elastomeric filler, tape all seams bedding the tape in a coat of EPA-approved Elastomeric coating, before coating the whole area with same, two or three coats(all EPA approved, as we catch all rainwater in cisterns, and this is our house water.). This 'roof-coating' is formulated for warm climates (no-freeze zones), but I understand they make a liquid PVC product that might get you a membrane for your purposes. O.K., what I am recommending to my client is to cover this entire decking area with Wonderboard, or chipcrete boards, the masonry sheets. Fastening by adhering with construction adhesive and screws, staggering all joints, and, if possible, run opposite of the layout of the plywood. You will need to predrill with a masonry bit, and you will want all screw heads flush. Once you have the entire deck redecked with wonderboard, you'll tape all seams with mesh tape, bedding it with thinset, keeping the thinset smooth and flush, much like sheetrock mudding. This is a nearly waterproof membrane, now, and you're ready for tile. The difference between thinset and grout is their formulation. One is formulated for adherance properties, one is formulated for it's sealing properties. This is why tile's ceramic glazing does not extend down the sides of the tile. Once all tile is set, grouting should be forced into the tile joints by passing your grout float in different directions over each joint. This forces the grout into, and actually underneath the tile, effectively sealing it. Once a complete and thourough grout job has been done, look into various sealing products. I have used all kinds of tile sealants, but the kind you'll need will have a 2-3 day cure time. That is just my own personal benchmark; Longer cure time = Most effective sealant. This sealant should be applied every couple of years after, depending on traffic, UV degradation, etc., but will remain sealed for many years. Hope this helps!
While not affected by water, grout itself is not a waterproofing material, and neither is thinset or wonderboard. All of these will allow moisture to pass through the materials into the substrate below, especially if cracking develops in the grout or tiles. You need some sort of additional waterproofing membrane, ideally a trowel-on membrane applied over the wonderboard before the tile.
There's an article in the new JLC (apologies to the FHB editors) about this topic and the author uses a three-part cementitious waterproofing membrane made by Life Deck (www.lifedeck.com) that looks very interesting. It is applied in three steps directly over plywood and ultimately is finished with an acrylic topcoat. This is the first I've heard of this product but their website has a lot of information, it's something I'd like to try out at some point.
AndyL...thanks for your input..I'll checkout Life Deck...Thought Doc's input on Hot mop built up worthy also.
being a comm. roofer for 27 years with the last 6 doing nothing but repairs , Iwould strongly reccomend staying away from any single ply roof system. The single ply craze was created by ease of application and very little equipment needed to apply the products. the idea of a roofer with a 500000 btu open flame on a wood structure has just never made any sense to me. torch applied roofs on wood structures usally fail because the roofer is more likely to use less heat than needed to apply to be and safe side.EDPM roofs puncture way to easy to be used under any kind of patio they also have shrink factor that most people are not aware of(1-3%over life of product relative to size of sheet) If the roof was mine I would start with a heavy organic base sheet nailed to the deck followed by 3or4 plys of fiberglass felt in hot asphalt than apply a smooth sbs base sheet in hot asphalt as wearing surface. As extreme as this seems when you think about what it would cost to remove the systems above the roof to repair the roof if a leak does happen the cost becomes a liitle more reasonable .
Thanks for your input.. I'll certainly get a quote from a hot mop specialist...while you're not in our area, what would you estimate top bid should be on such a job?
projects of the nature of yours usally will go for $3.50 TO$4.50 per sqft. the price will vary due to set up conditions,degree of detail(wall flashing details, if metal is needed)and time of year, here in michigan the best pricing comes in the spring of the year when contractors are hungry due to winter slow downs. good luck with your project