Tech Tip Tuesday – August 15, 2017

Q: Right now, I have engineered hardhoods that float over a concrete slab (second floor/above grade).  There have been water leak issues every one to two years usually in summer since I moved in 7 years ago, and no one seems able to fix it.  I’ve been told the water is getting in through the door, or from flashing outside, or from the slab below as water vapor, or that the aluminum slider is leaking/sweating, and that sunlight could also be making it worse.  I’ve never actually seen any water, even when the slab was exposed for several months two summers ago with frequent heavy DC thunderstorms (just a small area of wet concrete once and the discolored and cupping wood, which scrapes against the door).









What I hope to find is a solution that will work regardless of the moisture source.  I’m not a pro but propose cutting a square for an entryway there and installing outdoor rated porcelain tile (2 that are 12 x 24 or possibly 4 creating a two foot by four foot entry — although I prefer the smaller option).  The tiles would be surrounded by schluter strips, then the existing wood beyond that.  So here are my questions:

(1) Do you think that will work?
(2) If so, should I seal the concrete (maybe with Redgard), or will that make any potential water vapor migrate further into the unit and damage the hardwoods?  I’d rather have tile issues than wood issues at this point so I don’t have to replace the entire wood in that room.
(3) Any other advice?



Thank you for contacting me at the National Tile Contractors Association.

You should not be seeing any water coming in through or under the door sill or into the concrete like this.  The problem of water entering the structure needs to be resolved before installing any floor surface.

In my opinion your problem could be with the door itself, or the installation of the door, or the installation of the deck and it’s framing, or the installation of flashing at the exposed edge of the slab, or any combination of these things.

I have seen this problem before. The subfloor kept getting saturated every time it rained.  The finish floor could not be installed.  The problem was improper installation of a very expensive door unit by the general contractor.  The contractor figured they had installed hundreds of doors and they didn’t need to follow the manufacturer instructions.  After numerous attempts to add more sealant and after removing and replacing the door at least two times, a manufacturer rep came onsite to monitor the installation a third time and, using the printed instructions for the door, directed the contractor on it’s installation.  Problem solved.  The door never leaked again.

Here’s a simple test you can try. Spray the door and sill with a hose or sprinkle water on it with a garden watering can to mimic rain.  Does water come in?  Does it come in under/through the sill?  Does it come in through the door sweep?  If it does, there is a problem with the door / sill and/or it’s installation.  Again, no water should come in under the sill or through the sweep or other door component.  I encourage you to contact the manufacturer of the door unit and obtain their original installation instructions and attempt to determine whether the door was properly installed.  You may have to have the door removed, examined, and reinstalled using the instructions to make this determination.

As you have already been advised, the water intrusion may be originating with the flashing (or lack of flashing) and/or the deck installation and/or the installation of the sill and door.  Water may indeed be gathering in the leading edge of the slab under the deck and becoming saturated and wicking into the top corner of the slab and up under the sill and into the subfloor area.   You need to have that issue properly examined and properly resolved.   I recommend hiring a recognized, licensed, experience, trusted general contractor and have them give you a proper inspection and strategy for correction.  Be prepared to have them remove some deck boards to see what’s going on there.

You need to get the problem fixed that is allowing the water intrusion before you make a decision as to what to do for the floor finish.

There are methods to go about installing the tile, but you don’t want to have water intrusion into your structure. If left unresolved it’s persistent presence may likely  create other, as yet unforeseen problems.

After you have resolved the water intrusion and decide that you’d like to install tile, please get back in touch and I can help point you in the right direction for a proper tile installation.

I hope this helps,

Mark Heinlein, NTCA Trainer/Presenter