The tile installation on this deck has failed because the original tilesetter failed to create a positive slope for water to drain and didn't apply waterproofing. (Waterproofing is required for exterior projects over living areas, but I like to use it in all my exterior tile work because of our extreme weather conditions.) The slate tile and mortar bed have both absorbed water which in this case is the major cause of the failure.
The mortar bed between the tile and slab is saturated with moisture. Even if it were to only rain once a month this tile system would still never completely dry out. In the winter when it freezes the moisture content expands and damages both the tile and mortar bed.
There is other structural damage as well. Because the mortar bed has been saturated for so long, moisture has made its way into other parts of the structure by "wicking".
As you can see here, moisture is finally releasing from the exterior walls and beginning to dry out.
Unfortunately the damage is already done.
I'm not sure what I'll do here yet, probably mud the walls and apply Kerdi waterproof membrane.
I'm applying a "slurry" which is a thin mixture of thinset mortar to bond the new mortar bed onto the surface of the slab.
The screed will be about 2 inches thick along the wall which will be the top of the slope.
I've built the screed several feet along the wall to start.
Then I bridge the lower portion (bottom of the slope) to the higher screed to make sure I have a positive slope.
After the 2 sides are where I want them I start the end section to connect the two.
The mortar bed is done.
The next procedure is to apply waterproofing. Here I've used Ditra.
I've installed strips of Kerdi membrane to seal the seams of the Ditra.
The area of the wall between the patio floor and sill of the door must also be waterproofed so that water can't seep down between the wall and slab to cause damage.
Kerdi does the job.
Bill is staying back 2 rows of tile because it looks like we may get rain and I want to be able to lay out a sheet of poly to keep everything dry.
I'm working behind James to keep everything covered.
"Hurry up James .... those rain clouds are getting dark."
That's as far as we go today.
I used an edging profile with a "drip lip" manufactured by Schluter. Click on the link below to learn more about the product and application.
All that's left is grouting.
Look down to the end of the balcony and notice the slope of the tile in relation to the railing.