Replies

1. 
   Gabe_Martel | Dec 08, 2001 05:38am | #1

   *
   Yes,

   Gabe

1. 
   Tim_Kline | Dec 08, 2001 08:40am | #2

   *Yes, but you must lay the wonderboard in thinset using the notched trowel recommended by the manufacturer and then nail or screw.

1. 
   Tracy_Kiel | Dec 08, 2001 10:44pm | #3

   *What about the thinset dripping between the sub floor boards? Should I just have my sister stay in the basement to catch it?

1. 
   Rich_Beckman | Dec 09, 2001 12:51am | #4

   *Not as much will fall through as you think, but if it is a concern, I would just lay some newspaper down to catch it.Rich Beckman

1. 
   Tracy_Kiel | Dec 12, 2001 04:42am | #5

   *Thanks for the info, Rich. This may be easier than I thought and my sister is relieved she won't be trying to catch thinset in the basement.

2. 
   Scooter_ | Dec 12, 2001 05:30am | #6

   *The advice is wrong or I am confused.Assuming the subfloor is like 1x8's laid diagonally, and there is ply over that, there should no dripping at all.I also could not give any advice as to additional underlayment without knowing size and spacing of floor joists and condition and size of underlayment.If these are 2x8's 16oc with 1/4" ply over a damaged subfloor, the tile job will fail by cracking.The diagonal type subfloor was fairly common pre-war, and is prone to deflection for two reasons: (1)The span of the boards is greater than if they were laid at 90 degrees to the joists; and (2) They are not T&G. Without additional information, I would insist upon a minium of 3/4" ply over that floor before installing CBU's.Hope this helps.

3. 
   Tracy_Kiel | Dec 13, 2001 11:41pm | #7

   *Scooter, The joists are 2x8's 16"oc. The sub floor is 1x6 or 1x8, non T&G, layed diagonally. I don't know if the sub floor has any damage. The flooring is sheet vinyl. The underlayment is plywood: I'm not sure if it is 1/4" or 3/4". My sister wants to replace the vinyl with ceramic tile. Some of the underlayment is damaged and will have to come out. Since I have to remove some of the underlayment, I wanted to know what, if anything, should go under the cement board, because it didn't make sense to just patch it if what is there as underlayment isn't sufficient for cement board. Given the floor joist and sub floor configuration, you recommend putting down 3/4" plywood?

4. 
   Scooter_ | Dec 14, 2001 12:09am | #8

   *2x8's at 16" oc will be pretty springy, depending on the span and presence of blocking. Rule No. 1 on tile: Springy substrate means cracked tiles and grout.I sure would want to look closely at the structure and beef it up as much as possible. This could include: Ripping out subfloor and installing blocking between joists; or adding new subfloor (3/4" T&G would be absolute minimum.Without looking at your floor and without knowing the load above and the span of the joists, I would say, rip out the vinyl, look at the ply, and make a determination based on deflection what has to be done to beef up the structure to accept tile. My personal favorite is 1 and 1/8" T&G subfloor flooring. The stuff is absolute iron, and will not deflect. I can't say more, 'cause I can't see your floor.

5. 
   Crusty_ | Dec 15, 2001 06:23am | #9

   *I keep hearing/reading "thinset" -- I'm using Versabond "bonding mortar" -- is this the same thing? It's got polymer-somethingorother in it. Seems plenty strong, and you just mix it with water. It is not that "thin" when mixed (certainly not going to drip). I mix it stiff enough that it doesn't slump when troweld out (notched).If this is in a bathroom (assume it's rather small), couldn't you just scab some 2x10's onto the side of the existing 2x8's? I'd still go with at least a 3/4 plywood subfloor, with Hardibacker over that.

6. 
   Tracy_Kiel | Dec 15, 2001 06:15pm | #10

   *What's Hardibacker?

7. 
   George_Roberts | Dec 15, 2001 08:02pm | #11

   *Tracy ---Most of the advice you have been given is overkill.You might be better served by reading the documention provided by the thinset/tile/grout people.That documentation provides the goals you need to reach in the subfloor. I believe that l/360 or less deflection is required both along and across the joists, and there needs to be some conrol of joint movement.The documentation is printed on brochures and product wrappings.

2. 
   Tracy_Kiel | Dec 15, 2001 08:02pm | #12

   *
   My sister has some water damage around her toilet that necessitates removing some of the vinyl flooring and underlayment. After this is done she plans to install ceramic tiles. The sub floor is non tongue & groove 3/4" boards laid diagonally to the joists. The underlayment is plywood; I'm not sure if it's 1/4" or 3/4". I know that I should put down cement board for the new tile, but if I have to remove all the vinyl and old underlayment can I just put the cement board down over the sub floor?