Replies

1. 
   j_scalia | Jan 09, 2011 03:42pm | #1

   What I'd probably do

   Ok,

   You'd probably be much better off installing the tile directly on the basement concrete, but i suppose that would cause you elevation problems with the rest of the floor. If that's the case, and if you're absolutely certain the a floor sheathing is installed correctly, then the standard method for installation should be:

   1) Concrete backer board (Durock, Hardie-Board, etc.) installed on top of the floor sheathing, make sure you use galvanized or exterior decking screws to secure the board to the floor.

   2) Fiberglass tape all seams and skim coat with thinset.

   3) Set a thick mortar bed using 1/4" square notch trowel and install an isolation membrane (Schluter or other) in that bed

   4) Finally, set your tile in an appropriate mortar bed for the tile type and finish (grout and seal) like normal.

   Being this is in a basement, you might wish to consider radient heat in the floor. If you do, it would go in the mortar bed immediately under the tile.

   In all events, check with your tile supplier for their recommendations.

2. 
   xxPaulCPxx | Jan 10, 2011 01:00pm | #2

   Those others are thinking in terms of a 24" OC supported floor, not a floor continuously supported by rigid foam.

   Taken from another site:

   "We take a string and anchor it with nails across the longest span of the involved room. We anchor that string at either end with nails or in some way to allow the string to be tight. We carefully measure the distance from the bottom of the string to the surface of the floor. Next, we put the estimated load in the center of the room and re-measure the distance. If the distance exceeds the maximum requirements, we need to make some hard decisions.

   This process seems very difficult and laborious to achieve. When should we go to this trouble? Well, a simpler test is also available and is much easier. If you stand in the middle of the room, jump up and down, and feel the floor move under your jumping weight, chances are there is a deflection problem. If you wish to proceed with stone or tile more testing may be necessary."

   Here is another:

   "Tired of seeing guys jumping on floors to see if there is any movement? I am sure that if you showed up at the site, there would be plenty of movement. As for the measurement, put a dial indicator under the floor, set the dial to zero and then add 300 pounds of weight to the middle of the floor. If it deflects more than 1/360th of the span, the joists are not adequate."

    

   I don't think you will see any deflection at all.

3. 
   Clewless1 | Jan 11, 2011 09:06am | #3

   How about filling in between the sleepers w/ concrete, then hardie board fixed to the sleepers then tile? Maybe someone can tear into this comment. But if the insulation is supportive, I don't know why it would be a problem to simply remove the wood flooring and put down the hardie board and tile. Rigid insulation can support a lot when the loading is uniform like this.

   Putting hardie and tile on top of the floor may give you problems w/ elevation.

1. 
   DanH | Jan 11, 2011 09:47am | #4

   I think the problem is that the foam is apt to be a bit thinner than the sleepers.  If you're suggesting, though, to "grout" on top of the foam to bring it up flush, that should work pretty well.

4. 
   sapwood | Jan 11, 2011 11:21am | #5

   The first thing I'd do is put a really good straightedge on the floor, get a couple of heavy friends to stand mid-span of the straightedge, and measure the deflection. Do this in lots of places until you find any weak spots. If the system passes this test then start tiling. If not....... Maybe you could use a bunch of concrete fasteners in between each sleeper. Install the fasteners so they will suck the Adventech down to the foam. Now you will have a series of shallow dips in your floor. Trowel on thinset and screw down some backerboard. Then more thinset and tile.

5. 
   AVR | Jan 16, 2011 06:47pm | #6

   Add sleepers?

   Since you are adding a new basement bath, I'm assuming nothing is on the floor yet.  Are the toilet and bath waste lines plumbed already?  I think I would pull up the t&g and add more sleepers, or if I could determine the spacing wouldn't be so bad, add another layer of plywood to stiffen it even further.