Replies

1. 
   Dennis_Lewanowicz | Dec 27, 2000 04:40am | #1

   *
   Dear Hankoes,

   The reason for Durock is to stiffen a wood sub floor, walls, etc. Why would you want to stiffen up a concrete floor? Do you plan on laying tile?
   if so just lay the tile directly on the concrete!

1. 
   hankoes | Dec 27, 2000 04:29pm | #2

   *The reason is that the contract calls for it under the tile - reason unknown .

1. 
   Creature | Dec 27, 2000 07:52pm | #3

   *Durock and other backerboards do nothing to add to the structural properties of any subfloor or wall. You dont install backerboards over concrete. If tile cannot be installed on the concrete slab for any reason...cracking, out of level, sealers, etc...you need to repair the slab. Your options are things like crack isolation membranes, mortar beds, shot blasting, or removal and replacement of the slab.Dave

1. 
   Tim_Kline | Dec 29, 2000 06:55am | #4

   *b WBA At Your ServiceOur tilesetter has built up several concrete floors to match elevations by applying thinset to the slab and laying 1/4" wonderboard directly in the thinset. No mechanical fasteners were used, and it held very well. I would do this for height reasons, but not just because the contract says so. Unless there are unusual circumstances, I would try to talk the designer out of this brain freeze.

1. 
   Creature | Dec 29, 2000 05:33pm | #5

   *Tim:Your tilesetter is doing you a disservice by completing voiding the warranty of the tile floor that was installed. How long have the floors been in use? The appropritate way to raise the height of a concrete floor slab is to float a mortar bed. Dave

2. 
   Tim_Kline | Dec 30, 2000 06:59am | #6

   *b WBA At Your ServiceDave, 5 years or more. Void a warranty ? From whom ? Are you comfortable floating a mud bed that is 1/4" thick ? Our tilesetter is not. Where do you see the problem here ? The lack of fasteners ? With extra effort he could use flat head Tapcons to anchor the sheets.

3. 
   Creature | Dec 31, 2000 12:20am | #7

   *Tim:Warranty on your tile for starters. Do you warranty the installation? Or does your installer? If so, how long? No, I would not float a mortar bed 1/4" thick but I would also never adhere backerboard to a concrete slab. How are you checking for 100% coverage? Why do you need to raise it up a 1/4" anyway? Sounds like a planning problem to me.Dave

4. 
   Tim_Kline | Dec 31, 2000 09:58am | #8

   *b WBA At Your ServiceDave, Are you saying that if I call the tile manufacturer, they're going to tell me that we're not allowed to attach backerboard to a concrete floor ? What's the difference if we attach it to a wood subfloor or a concrete slab ? Yes, we warranty our work. The duration is generally a year, but it is very rarely used. "Why do we need to raise it up 1/4" anyway?" Geezowhiz, Dave. I guess you must only take on work where conditions are perfect. Building up a slab 1/4" with backerboard sure seems like a simple and inexpensive fix compared to the alternative of jackhammering a customer's family room floor.

5. 
   Creature | Dec 31, 2000 04:06pm | #9

   *Tim:Geezowhiz(nice word BTW) Tim, getting a bit defensive?! Yes, the tile manufacturer would not warranty their tile because this is not an approved backerboard installation. You do realize that there are published standards for tile installation? There are materials available to increase the height of your floor instead of backerboard..i.e, self leveling compounds, floor patch mixes, etc. You seem to comfortable with this type of installation and apparantly it seems to be working. I wouldnt do it. If I install a tile installation over a mortar bed it gets a lifetime warranty. Backerboard installations get a 20 year warranty, the same length as the backerboard if installed according to their specifications.Dave

6. 
   Jim_Malone | Dec 31, 2000 05:16pm | #10

   *Laying a straight edge on a concrete slab can be an eye opening experience. Radical peaks and valleys, crowns and twists. As a general rule, this is not the substrate that I prefer for a primo tile job. Float a mortar bed with some screed action -- sure, it will work and is a system on which you can depend. Some of us still float out our shower walls. Lately, I have been using more and more backerboard, establishing systems and making it work and work it does. Just common sense. If in dout apply a concrete bonding agent to the slab first (kinda like sanding that glossy paint before repainting). Trowel on the portland cement based thinset with a trowel that will give full coverage based on the slabs finish(this is not rocket science). Backer board goes down and use a consistant system to assure that it is at least encouraged to seat over its entire surface area. With some good music, a little dance would work just fine. On occasion there may be an edge that won't lay down properly. Powder activateds are ideal here. Get some superwide, tiny hole fender washers at the hardware to supplament the washers that come with the pins. The right charge and these guys will counterbore themselves just below the 1/2" durarock surface. These can be used if needed but sparringly. Another option is to hammer drill and use anchors and screws or Tapcons. This can be a pain, with wet mud and old hard-cured slabs.I always tape and mud my cement board joints. Fiberglass self stick sheetroc tape and the same mud that I'm going to set tile in.I do use mud and grout with a bit of admix (not the high priced stuff but not the cheapest (no-flex) either. I can get a much better tile job this way every time without alot of backbuttering and prying up and I'm not worried in the least about failure.If the slab has an expansion joint in it that shows any sign of prior movement, I will start my backer board from this groove leaving one continous seam which I don't tape and also arrange a grout joint above which I fill with silicone (clear, when in dout) caulk on setting day. The next day on grout day, it won't fill in much and I've never had anyone complain when they understand the reason.Good Building,Jim Malone

2. 
   hankoes | Dec 31, 2000 05:16pm | #11

   *
   Used Durock on top of linoleum, leveler, screwed down, etc. However, on concrete is new to me and I can't find any reference in any thing I've looked at. What needs to be done to level, adhere Durock to a bare concrete basement floor ?????