Replies

1. 
   seeyou | Dec 21, 2002 01:18am | #1

   The Hardibacker I've used is 1/4". There's not much difference in price, so if height is not an issue, I'd stick with the concrete board. I don't have any good reason for this other than I tend to stick with products that are road tested. That being said, I've eagerly used Hardibacker when I need to gain a 1/4".

2. 
   92588 | Dec 21, 2002 01:43am | #2

   i would add 5/8cdx df then call a good tile guy for a good mud job. raise the doors and have fun making the oak reducers to other rooms

1. 
   JeffBuck | Dec 21, 2002 11:39am | #3

   no need for a mud job..that's why they invented backer board...but I'd thicken that 1/2" first.

   Jeff

   Buck Construction   Pittsburgh,PA

    Fine Carpentery.....While U Waite                  

3. 
   andybuildz | Dec 21, 2002 02:07pm | #4

   gh

      I'd add some 3/8 cdx ontop of everything then go with 1/2" Wonderboard thinset and screwed on top of that. I'm partial to "Wonderboard" as its heavier than any other CBU I've ever used and my gut feeling is that it makes for a better job. No need to mud job it IMO.

   HAve fun.

              Namaste'

                            Andy

   One works on oneself, always. That's the greatest gift you can give to community because the more you extricate your mind from that which defines separateness, that defines community. The first thing is to become community. "Ram Dass"

   http://CLIFFORDRENOVATIONS.COM

4. 
   ikeeptryin | Dec 21, 2002 05:23pm | #5

   to the best of my knowledge, you need 1-1/4" of wood for a sound base.

   after that, no need for wonder, hardi, or anything else.

1. 
   Seth_Frankel | Dec 21, 2002 05:54pm | #6

   I'm facing the same decision in my bathroom remodel. I'm tearing out the floor, sistering the joists to level the floor (110 yr old house) adding subfloor and tiling. I've got to make up a total of 1.5" including tiles (4x4 terracota with 1/2" grout lines).

   A contractor told me that he'd suggest two layers of plywood screwed and glued and tiling directly over top. He said that stiffness is more important that the qualities that cementious backers give.

   What benefits are there to cementious backer boards? Seems like the only one I can think of is tooth for the thinset. If they are screwed and glued down don't they add stiffness like plywood or do they not have that kind of integrity?

   So, 2 layers of ply or ply and backer? Suggestions?

   Thanks.

   Seth"Nothing is a

   mistake. There is no win

   and there is no fail . . . there is only

   make."

   John Cage

1. 
   Justus | Dec 21, 2002 11:49pm | #7

   Stiffness is very important, but so is seasonal stablity. Hardibacker comes in both 1/2 and 1/4 thickness. ( i use 1/2 when I am using it alongside sheet rock for example)

    I don't like wonderbaord nearly as much as hardibacker, it is more difficult to cut cleanly and is more irregular than hardi. I to me hardi and tile are simply one unit, I would never use tile directly over wood because of moisture and movment problems. especially in a bath/shower situation.

   I but down at least an 1 1/4" of plywood screwed and glued, and then 1/4 hardi backer. I also seal the edges and seams with caulk to create a water proof platform for whatever is placed above it.  

   Justus Koshiol

   Running Pug Construction

1. 
   Redfly | Dec 22, 2002 12:24am | #8

   I'm with Justus on this - I much prefer Hardi to Wonder and for the same reasons he mentioned - it just seems flatter and is much easier to work with.  As far as tiling directly over plywood in a bathroom, I think that's job security, since you'll be back in a few years to tear it all out and re-do it with backer bd onaccounta all the rot.  Most tile/grout systems are not truly waterproof (especially unglazed terra cotta), so the idea is to not let the water penetrate through to the permeable surface beneath, i.e., plywood.  I treat bathroom floors like a balcony over occupied space, but then again, I have a couple of kids that think 'draining the bathtub' is a matter of splashing it all over the floor.

   I also like the thinsets that offer some flexibility, i.e. Flex-Bond, since they can handle a little movement without cracking. 

5. 
   Redfly | Dec 23, 2002 01:29am | #9

   IMO, additional plywood is desirable, but not necessary if you use 1/2" hardi-backer or wonderboard (assuming joists min. 16" oc).  Additional plywood or OSB will provide stiffness, which is important in tile installations.  Sometimes, of course, the additional thickness causes other problems, i.e., matching floor heights in adjacent rooms.  In that case, I would stick with 3/4" CD and use 1/2" backer.

6. 
   wrick2003 | Dec 23, 2002 03:28am | #10

   heres how we did our last kitchen job with radiant floor heat:

   1. all of the floor boards were removed down to the joists.

   2. 2x4 nailers were attached 3/4" below the xtg joist height. carry a 3/4 scrap as you dance around the room as a guage, and you can shoot those babies on in no time.

   3. put fiberglass bats between all of the floor joists

   4. cut several strips of 3/4 plywd, NOT cdx, and shoot them all on between the joists onto the nailers, when you are done, the entire surface has been lowered.

   5. staple down 15 or 30 lb felt over the entire surface.

   6. staple expanded metal lathe over the entire surface, stapling also the overlapping edges.

   7. staple down tubing as required by the manufacturers guidelines, taking care to locate your manifold in a logical location in the basement. don't put the tubing under the cabinets.

   8.pour and level your mud base. don't mud yourself into a corner (heehee) keep in mind that you could have a great difference in mud thickness from one end of the room to the other.   

   9. you can begin laying tile the next day

   this may seem like a helluva lotta work, but when it comes time to fabricate the thresholds, or trip-steps in the adjacent rooms, you will appreciate the smaller difference in height. and it looks alot better too.

   i hope this is helpful. we have done this on several jobs, one of which was about 3" out of level across 9 feet of floor.

   merry christmas.

1. 
   gbwood | Dec 23, 2002 04:41am | #11

   ricky is rite- the proper way

1. 
   Boxduh | Dec 23, 2002 07:08am | #12

   Take a look at Schluter's "Ditra" fabric underlayment.  It is what everyone is using here where I live and work.  No wood, no cement board, just a waffle membrane that does what you need when the substrate structure moves where you don't want it to.  Do the Germans and Swiss have tile in their homes?  Do they use this stuff?  You bet they do.