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Question DetailsAsked on 12/16/2016

Leaking deck roof

A tile deck out of second story bedroom is leaking to the patio underneath it and causing door problems

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2 Answers


Two likely causes for this:

1) Leakage at the perimeter of the deck, especially at the edge along the house wall, causing water infiltration down along the wall to the patio door below. Can occur because of blowing-in water or melting drifting snow against the house getting past the flashing and ice and water shield which should be there, or sometimes due to settlement resulting in the deck tilting towards the house and causing ponding along the hosue which overtops the water barrier at that point. Since you say your problem is at the patio door, sounds like ti might be a perimeter flashing/waterproofing issue - possibly even runoff down the siding which is getting down past the tile to the patio door and is not the fault of the tile surface at all. NOrmally the waterproofing on a tile deck goes from the behind the wall siding down under the tile to end up in its drainage layer - with metal flashing tucked under the siding and extending out over the tile to take the surface runoff out away from the wall. This can commonly be retrofitted with ice and water shield and metal flashing both up behind the siding (the ice and water shield behind or adhered to the house water barrier depending on whether the wall water barrier ends at that elevation or not, to catch any water running down behind the siding), and the metal flashing right behind the siding to divert external siding runoff out onto the tile (assuming the tile does not slope toward the house of course). Installation of these would be preceded by long-life silicone caulk cualking the actual crack between house and deck UNLESS the deck was build with proper drainage system between it and house, in which case that gap (typically 1/4" or so), IF backed up by proper ice and water shield or flashing, stays open as a backup drainage point - or unfortunately, the primary drain if the deck imporperly slopes toward the house. Detail here for that case -

2) Leakage through the tile surface:

Contrary to many people's understanding, tile floors are NOT waterproof - only water resistant and then only for relatively short exposure periods - so while they might seem basically waterproof for taking a shower say, try them in a soaking bathtub or hot tub or out in prolonged rain on a deck and you find it is far from "waterproof". So tile floors should be made with proper sloping water barrier (either on sloping base surface or on a sloping dry-pack mud coat), then for outdoor or prolonged water exposure uses a drainage layer above the water barrier, then the base layer (usually a "dry laid" concrete dry-pack porous mud coat), then the bonding layer (usually exterior epoxy or plastic cement thinset for outdoor use), then the tile, then filling of the tile joints with the proper type grout for the tile and application - commonly an epoxy or plastic cement grout for exterior use with porcelain or ceramic (as opposed to clay) tile. Of course, for applications like on-ground patios or decks where it does not matter if leakage passes through, then the drainage layer and water barrier is commonly skipped and the mud coat is just made to be sure it is porous and the base is sloped, like the base coat in a shower, so water getting through can pass through it and drain away.

In much modern construction for expediency and reduced manhours, and on some decks where limiting weight is important, the mud coat and drainage layer is skipped and the tile is applied directly to an underlayment plastic layer like Shluter Ditra or Provaflex or such - which commonly does not work well in any usage, but particularly tends to crack along the joint lines and leak in outdoor uses. Also, not having porous mud coat and deliberate drainage layer under the tile can result in ponding of water under the tile, which in freezing weather than results in cracking along the joints or even sometimes popping up of tiles and cracking through the tiles.

GREAT care also needs to be taken if built on wood deck (always a bad idea) so the wood does not rot out quickly - generally needs an air-permeable base mat under a totally waterproof heavy membrane which is properly drained off the wood area to prevent rot in the deck - and of course ALWAYS ground-contact treated timbers and plywood in that application.

One other thing critical to minimizing water intrusion through the tile is expansion joints (silicone caulk filled) about every 5 to not more than 10 feet (that is really too far in most cases), and if the concrete under it has expansion joints putting the tile expansion joints directly over the concrete joints.

Solutions to your leakage - short of pulling the tile up and finding the leak by basically redoing that area (or the whole tile surface sometimes), about all you can do is have any cracked or missing joint grout cleaned out and regrouted with exterior rated water-resistant (usually latex or epoxy modified) joint grout, thorougly clean and degrease the tile surface, then use a "flood sealant" (in higher quality work usually preceded by a penetrating sealer) - which is a liquid (usually silicone or silane or mono-polymer based) sealant designed to be squeeged over the tile surface to seal any cracks or pinholes in the grout or tile. This is not a regular grout sealer - this product is designed to adhere to both the grout in the joints and to the tile and to provide a waterproof seal over the entire surface. Typical life maybe 1-2 years max in outdoor use - and they have the disadvantage that they scratch and fog with wear and exposure so you get a whitish fog or haze appearance on the tile surface fairly quickly, and most tend to be more slippery than tile when wet. So the flood sealants, unless you redo it basically yearly or even more often in severe weather environments, are not a permanent fix for the leakage issue - though will certainly will reduce the amount of water getting through, and are not real tough to reapply yourself if you are careful to properly clean the surface first so it does not fail to adhere and form bubbles.

Note - I do NOT recommend using the "general purpose" silicone sealers like Thompson Waterseal or Trewax or such - not only do they tend to not stick well to tile, but will generally whiten quite quickly in outdoor use, and most of them have dubious lifespan - I have seen them cracking and peeling off in weeks after applications in severe sun exposure situations, and the water based ones like Thompsons tend to not really waterproof thoroughly at all even when first applied. For outdoor use, to expect any sort of life, water-based products generally are not good performers.

Ceramic Tile would be your Search the List category for a repair person - and be sure to get one who does a lot of outdoor deck tile, not just bathrooms and kitchens.

BTW - exterior grout - International Tile and Laticrete both make latex and epoxy modified grouts designed for different types of stone and tile - the particular type has to be matched to the product - generally epoxy modified is stronger and more waterproof but is too strong and hard for soft clay and quarry type tiles, so latex modified is usually used for them. Flood sealers - there are a number of impregnator (penetrating) advanced silane and polymer sealers out there from tile manufacturing and chemical companies - I prefer the DuPont StoneTech and Bulletproof Pro lines of stone and tile sealers, especially the non-water based professional ones - though many customers freak out when they see the $50-180/gallon pricetag (retail cost BEFORE contractor markup) depending on which product you are using. (There are about 10 varieties for different environments and different flooring products - selection guide at manufacturer website). Again, International Tile and Laticrete makes some good silicone based ones too. Generally, for outdoor use, the water-based ones are pretty useless - you need a more advanced solvent-based product to have a prayer of it adhering correctly and lasting, commonly a two-layer process with a bonding agent or impregnator coat first to actually waterproof the flooring and grout, then one to three overcoats of the surface water-shedding and protective coating material, paying CLOSE attention to instructions on application temps, acceptable ambient humidity (put on in damp weather and it can blister and not adhere and turn white), curing time before next coat or first use (commonly 6-24 hours to recoat and 3-7 days before use), etc.

Answered 3 years ago by LCD



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Answered 3 years ago by Member Services

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