Can anyone please direct me to making a sound decision on which backer board to use. Is the old stand-by Durock the best or is Denshield a good alternative?...I've heard and read lots of good and bad on the modified drywall product and just wondering if it is indeed a "junk" product?
I haven't gotten brave enough yet to use Denshield on floors, even though it is rated for that use. I think it's perfectly fine on walls that don't get wet, or even on walls that get wet as long as the instructions are followed concerning sealing the edges with silicone to prevent wicking into the gypsum core.
This is just my opinion, though. There are lots of tilesetters out there that love the stuff. I love it, too, when I'm doing a job on a third floor (it's easier to cut and handle).
Thinset doesn't seem to stick to the surface as well as with mud or cement board. Mastic sticks just fine.
Because I had mud work beaten my head by Michael Byrne and because I warranty most of my jobs, by default I try to sell mud work to my customers.
But budgets are often a concern, and choices have to be made. Nesxt to a mud job, i'd prefer cement board with a waterproofing membrane. After that, cement board with vapor barrier. Finally, Denshield is my last choice. (Hardibacker is not widely available in my area)
Denshield has been around about 10 years, cement board for 30+ years, and mud for 1000's of years.
I would not consider it a "junk" product, but instead would keep in mind what it is-a gypsum based product with a waterproof covering that must be sealed on the edges. Unfortunately, there is no way to seal each hole made by a fastener. Because of that, I wouldn't provide a very long warranty for a Denshield installtion.
The issue that needs to be addressed is what tiles and materials should be used for a particular application.
When properly specified, installed, and covered with tile according to industry standards, a Denshield wall installation is capable of providing the same level of service as a properly installed mortar bed installation. That is to say that Denshield will perform as its makers claim, but is not appropriate for every installation.
As well, I don't like understand why the makers of Denshield don't also market a silicone-based caulk or sealant that could be used to cover fastener holes and mis-hits, and be used to seal around the perimeter of plumbing or other penetrations. Combined with such a sealant--and perhaps a waterproof joint reinforcing tape--Denshield could be a much more versatile tile backer.
Don't let this sound like an endorsement of the product because it is not. My position on tile installation, though, is this: match the right materials for the installation, and install them correctly. This goes for mortar bed installations as well. As an installation contractor, I have to work with a variety of materials--not just my personal favorites.
I made a small fortune ripping out thousands of mortar bed installations that were installed improperly. Most had 15-pound tar paper "water-proof membranes" that leaked profusely. Same with cement backer boards. The problem with cement bases in wet areas is that they tend to mask structural decay until significant damage is done.
Most modern tile installation materials will perform as advertised, but it is important to understand each product's limitations and requirements.
Talk to the manufacturers making boards and membranes, compare the performance of the materials and then give a careful eye to the work you are doing: be conservative regarding wetness. wherever tiles will be exposed to moisture daily, include a membrane in the installation.
By the end of the year, there will be numerous synthetic boards with integral waterproofing membranes hitting the market. Denshield was the first board with an integral membrane but it won't be the last. With more and more specially-made, waterproofed, stressed-skin boards available, un-coated boards are soon to be a thing of the past.
Until then, regardless of the materials you choose, specify them realistically and install them according to their instructions.