Waterproofing Membranes in the Marketplace
by J. Zimmerman

Like many contractors who have been around awhile, I have installed tile using just about every method available.  After following industry standards of the time and installing many vinyl or rubber liner shower mud floors, I was looking for a better way.  This became especially true after tearing out a few showers to discover that a vapor barrier stapled behind board in the walls was not a very sound solution - there was too many instances of mold, mildew or rotting studs because of trapped moisture.
The variety of products available over the years for waterproofing a shower install boggles the mind.  However, I discovered Schluter and their Schluter Kerdi shower kit systems a few years ago and have favored these types of systems ever since.  Kerdi was a great idea!  Schluter devised a system that in the end created a seamless waterproof barrier from the drain all the way up the walls as high as you wanted to go.  Kerdi systems were even designed to waterproof the potentially problematic curb area as well.
Schluter Kerdi shower kits were far easier to install than rubber liners and double layers of sloped mud.  All of the Kerdi is installed just beneath the tile, so moisture cannot get trapped.  Schluter's waterproofing system allows a shower to completely dry out in days.  I've torn up concrete mud floors that retained moisture for weeks!  Schluter's introduction of a novel concept - a square drain - was an additional long overdue feature of the Kerdi system.
Some guys out there are using roll-on membranes like Redgard, Laticrete’s Hydroban and Mapei’s Aquadefense.  Although performance varies from product to product, cure time, getting consistent mil thickness, the amount of time to flood test and install tile and tendency for creation of pinholes are potential issues I prefer to avoid.  Some of these products out there tend to shrink or even get brittle over time.  Some of these liquid membranes only have a 1-year warranty while I am used to an industry standard 5-year warranty on membrane systems. Although all of these types of products are far better than vapor barriers behind concrete board or no waterproofing whatsoever, I sleep better at night using membrane systems like Schluter Kerdi.
The membrane world of Schluter Kerdi systems has not remained bright and rosy, however.  The material and shower kits are getting more and more difficult to find.  Many suppliers have apparently had some sort of disagreement with the Schluter company.  Places that still do carry Schluter Kerdi charge ever increasing top dollar for the products.  It seems nearly impossible to find competitive pricing for Schluter branded Kerdi these days.  Furthermore, it is becoming more and more difficult to complete high-end showers without using a high-quality modified thinset - thinset that Schluter strictly forbids on the use of Kerdi.
My search for better pricing led me to a similar product that competes directly to Schluter Kerdi.  Dural's Durabase WP (waterproofing) is virtually identical (it's yellow instead of orange) to Schluter Kerdi but can purchased at a much lower price.  I had never heard of this Dural company before and did a little research.  Apparently Dural has been competing with Schluter for many years over in Europe and England and has a pretty fair share of the market over there.  Dural simply is starting to introduce their products here in the states.  It appears that primary supplier of Dural Durabase products here in the U.S. is ProSource Center at prosourcecenter.com.  Even when shipping is considered in the equation, ProSource Center offers the Dural Durabase WP at a far lower price per square foot than Schluter Kerdi.
The best feature of Dural Durabase WP is that you can use modified thinset with this membrane!  This is a fantastic advantage, since I always try to follow the most modern tile-setting guidelines available.  The Tile Council of America (TCA) has recommended the use of modern polymer-fortified thinset mortar for setting tile for some time now.  I find that the WP membrane lays down and stays down much more easily with a good-quality modified thinset.  I also can rest easy knowing that these higher-end thinsets offer a much stronger bond, are crack resistant and will allow my shower install a better chance to stand the test of time.
ProSource Center has created an entire series of shower kits that use the Dural Durabase WP to directly compete with Schluter Kerdi kits.  I have enjoyed installing all of their variants, but my favorite is their Pro Advanced Shower waterproofing kit.  Like Schluter's Kerdi, it comes in 48x48, 32x60 center and offset and 72x72.  The Pro Advanced shower kit assortment also is offered in a 48x72, which I have found to be very convenient these days with the larger rectangular showers.
The best part of the Pro Advanced shower kit is their new drain system.  It's like a next generation evolution of the Schluter Kerdi original system.  The Pro Advanced drain offers a screw-less grate cover in ten different colors and has an integrated hair trap.  The best part though is the stronger flange that is designed to be fully supported at the base rather than by thinset up near the top.  It's also includes a waterproof adhesive to bond the WP membrane to the top flange.  This seems to offer an even better fail safe compared to merely thinsetting membrane to a fleeced flange.
Prices on the Pro Advanced shower kits are of course substantially less than a comparable Schluter kit.  Furthermore, the Pro Advanced kits can be customized - i.e. ordered without a curb if the install dictates.  And although I will always keep an eye out for new products that might come along, for now the Dural Durabase WP and the Pro Advanced shower kits seem to offer the best combination of performance and cost effectiveness.