Replies

1. 
   FastEddie1 | Feb 11, 2005 11:20pm | #1

   Slate, and other stone, is very intolerant of sub-floor deflection.  What size joists, how far apart, and what span?  Is it one layer of 3/4 ply?

    

   I'm sorry, I thought you wanted it done the right way.

1. 
   BOODOG | Feb 14, 2005 05:32pm | #2

   16" OC

   just the 3/4 now but looking for the right combo over that - should I put an extra layer of ply and then the backer board?  Basically how much should I end up with and what type of backer is best?

    

   Thanks

1. 
   FastEddie1 | Feb 14, 2005 05:40pm | #3

   16" oc, but how far do they span, and what size are they?

   Many people say that a total of 1-1/4" subfloor is required.

   The backer board  provides a good bonding surface for nthe tile.  If you have the height available, 1/2" is fine.  If you're tight for space, a membrane works well.  Noble CS is one, and DalTile sells it under their own brand name.

    I'm sorry, I thought you wanted it done the right way.

1. 
   BOODOG | Feb 14, 2005 07:11pm | #4

   yeah realized what you were asking after I sent the mail - 34' span with 11 3/4" size.  I am looking at 1/2 the span with a beam in the basement which would reduce the deflection significantly.  That said I have no problem going to 1 1/4.  I would use the membrane instead to keep it closer to the surrounding floor.

   Thanks for the advice!

1. 
   FastEddie1 | Feb 16, 2005 03:43pm | #5

   I'm not ignoring you ... but I am out of town and don't have my span tables so I can't say what ytour situation is.  But I strongly suspect that 34 ft with a 2x12 is too far for a stone floor.

    I'm sorry, I thought you wanted it done the right way.

2. 
   billyg | Feb 16, 2005 03:58pm | #6

   Unfortunately it's not going to make it with slate at a 17 foot span, and it's barely good enough for ceramic tile.

   See:http://www.johnbridge.com/vbulletin/deflecto.pl

   Billy

3. 
   BOODOG | Feb 16, 2005 06:45pm | #7

   Thanks for the info everyone - I guess it is back to wood floors in this area (no big deal!).  Glad to find out now instead of later with cracked and popped tiles!