How do we install a tile shower over a Wood Sub-floor to meet ADA Handicap requirements?


Can you give me you 2 cents regarding the tile install on a shower floor. It’s a wood substrate and they are trying to deal with ADA requirements and did not recess the shower portion.


ANSWER - For an ADA shower you can’t have a curb/dam.   You need a minimum slope to drain of ¼” per foot and no more than ½” per foot.   You need a two part drain with weeps for the primary waterproof membrane to clamp to.

Before the primary waterproof membrane is applied you need to install a pre-sloped bed.  You can put down asphalt building paper over the wood and nail metal lath and float over that to achieve the sloped base.  Of course the wood subfloor can’t have excessive deflection.   Then you apply your waterproof membrane and it should flash up the wall at least 6 inches and preferably continuous up the walls.   The membrane should clap into the drain and pea gravel or a plastic weep hole protector goes over weep holes.  Trench drains work good and can be put at the back of the wall.  Then float a wire reinforced mortar bed over that; preferably 1.25” thick, but it can work at ¾” thick under the right conditions.  We normally then apply a liquid applied waterproof/crack isolation membrane over the mortar bed and up the walls and ceilings if they are to be tiled.  Then bond your tile to the membrane.  Make sure all of your inside and outside corners are soft joints.  Use backer rod if practical as required.

You would then have to float the rest of the bathroom so the floor at least slightly slopes to the shower.  You can use threshold reducers at the doorway thresholds.  This provides extra protection in case there is every a plumbing leak in the bathroom it will drain to shower and into drain.

If you don’t have the height space to work with on the floor, you could do the building paper over sub-floor, metal lath and float to the height you need, with a slope, and use an integrated bonding flange drain and waterproof over the flange and up the wall, and bond your tile to it.   Bathroom floor still prepared the same as above.

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