Requirements for tiling floor with 24" centers? [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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12-08-2016, 01:40 PM
I have a house built in the 1930s. Floor has the old full-sized joists, which are 1-7/8" x 11-1/2". They have a 16' run with I-Beam supports at 8'. The I-beams are 4"x4" with 3/8" steel and span 12'. According to "Deflecto", ignoring the I-Beams, I have L/1386 (using 11-1/4" x 2" with 8'span). But I do feel some "bounce" on the floor so am concerned about cracks in tiles. I don't know if that is due to the I-Beams or the 24" span or both. One end of this room has 3/4" T&G 4x8 sheets of "Oriented Strand Board" (actually .703" thick) as subflooring. The rest of the room has 1x4 T&G subflooring.

The questions are:
1) How much should I add to the subflooring to make it solid enough for 2' x 4' ceramic tiles?
2) Is Ditra or Ditra-XL recommended for this application?
3) If I decide to go with hydronic heating in the floor (above the first subfloor but embedded in the next, what would be required to support tile?

Thank you for any advice on this job.

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12-08-2016, 04:01 PM
As a minimum, you need a second layer of subflooring unless you could support enough floor thickness required for a mudbed. If you can support a mudbed, to minimize the overall thickness, you might consider something like Schluter's Bekotec . Should you decide on that product, read their installation manual and follow their instructions.