Replies

1. 
   chiefclancy | May 05, 2002 07:35pm | #1

   I think it's just one extra insurance policy. While unaffected by water, concrete board certainly is not waterproof, and neither are many types of tile and grout. If the felt is sealed to the tub, the goal is that any water that gets behind the CBU (due to cracks in grout, etc), would hit the felt and drain down to the tub, never getting to the studs or ceiling below. It's not the best waterproofing solution, but it is cheap and simple, and can add years of life to an installation.

1. 
   lewandsallyh | May 06, 2002 02:59am | #2

   andy,

   have you tried georgia-pacific's dens-shield as tile backer?

   I've used it once and like its ease of installation( no weight)

   I'm looking for problems with it

   lew

2. 
   Scooter1 | May 06, 2002 04:12am | #3

   Some sort of moisture membrane is REQUIRED by the Tile Council and most Codes. I use 6 mil poly. It is thinner and you can see the studs. All CBU's leak, especially at the seams. It is an absolute must.

   Do not use Dens Shield anywhere near a shower. It is a gypsun product and will crumble when exposed to water.

   Regards,

   Boris

   "Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927

1. 
   chiefclancy | May 06, 2002 07:59am | #4

   First, I should point out that I am not a professional tile setter but instead a motivated DIY renovator. That said, I have usually gone with CBUs in shower stalls if floating the walls isn't feasible, but I have used Dens-Shield for tub surrounds and countertops. I like working with it, it's lightweight, easy to cut, and the mfg has great support for it. In my area, the panels are the same price as Durock, so the extra time savings can be meaningful.

   While it is a gypsum product, it is coated with a waterproofing membrane that makes it impervious to water penetration. Where you run into problems is when the edges aren't sealed (this is usually the biggest concern where tile meets tub). If water can get past the waterproof coating, it will rot out the gypsum core and then the installation will fail. Because of this I do not use it in areas that require more heavy-duty waterproofing.

   The key to dens shield working is to install it exactly in accordance with the mfg's specs, which among other things states that you should not counter-sink the fasteners (which would penetrate the waterproofing membrane), that the joint where tile meets tub (as well as inside corners) must be sealed with silicone caulk, and that the panels be tight-fitted when they're mounted (which is different than installing CBUs, which typically require a 1/8" gap between boards for expansion.)

   Dens shield would be vastly improved if GP came out with a liquid patch-type waterproofing material that could be applied over areas where you accidentally countersink a fastener or otherwise break the membrane. You could also apply something like this to the bottom edge of the panels where they meet the tub to prevent wicking. I suppose one of the trowel-on membranes cuttently on the market would work for this but I've never tried it. Usually these are sold in quantities that are prohibitive for non-professional setters.

   My two cents...

2. 
   AndyEngel | May 21, 2002 10:57pm | #5

   Boris, I used Denshield around my showers, as GP suggests the purpose of the product is. Before doing so however, I dropped a chunk of it in a pail of water. It was still floating when I took it out after about three weeks, and there was no noticable deterioration of the gysum at the edges. Andy Engel, Forum moderator