We have been trained by Schluter® Systems to install their products.
Why? We love their products and are satisfied that Kerdi, is one of the best shower waterproofing systems there is. We wanted to hear from them how to optimize our installation methods, to benefits both MHS Works and our clients.
In much the same way you can say it about many German products; Schluter® Systems have done an excellent job of solving the problems faced in their industry by properly by thinking them through and engineering solutions without conforming to preconceptions.
There is a reason why experts including Mike Holmes from the TV show "Holmes on Homes" stands by Schluter® Systems. But I was a skeptic and didn't take the hype as a fact, so I devised experiments and tested the materials myself. In one, I made a 12"x12" container out of standard 1/2" sheetrock, and lined it with Kerdi. This is not a fair test since a shower never holds a 12" head of water. (about 15psi) I let my drywall bucket stand for a week, with zero leaks before conceding that Kerdi and its thinset joints are indeed water proof in household conditions.
So what is Kerdi and where do we use it?
At its core, Schluter® Kerdi is a polyethene sheet that's inherently waterproof, bonded between two sheets of polyester fleece that provide the mechanical anchor for the membrane. It inhibits water from penetrating to the interior structure of your shower. In most cases the Kerdi family of products is bonded with premium unmodified thin-set mortar and so is compatible with anything you'd usually use thinset to bond to. The structure of the membrane is hydrophobic, and water beads up on its surface. Its vapor retardant properties also make Kerdi perfect for use in steam rooms and showers where the water is mobile as a gas. Since the assembly comprises of only inorganic materials, and holds a minimum volume of water, it does not promote the growth of mold and does not become impaired with time like other methods and materials.
To make installation faster and joints or unions more robust, Schluter® makes Kerdi available in several performed options for inside and outside corner joints, butt joints, mixer valve openings and pipe protrusions, Along with complete shower stall kits.
Kerdi itself comes in big orange rolls 36" wide. We use it on the walls, the shower pan and make shower niches with it. We apply it straight to drywall or even use Kerdi-board.
Schluter® Kerdi-Band is a narrow strip of kerdi used for butt joints.
Schluter® Kerdi- Kereck- F is used to seal inside and outside corners.
Schluter® Kerdi- Drain is an integrated drain for the shower pan.
Schluter® Kerdi-line is an integrated linear drain.
Schluter® Kerdi-Seal-PS and MV is has a rubber gasket for sealing around pipes and mixer valves.
In order for Schluter® Kerdi to be effectively bonded, it specifically requires un modified thin-set mortar. i.e. one that does not contain a modifying latex additive. The latex found in modified mortars holds water which has to leave the mortar either by evaporation or absorption into the other substrates in the assembly. Since Kerdi is waterproof, the water would take days to leave and the mortar wouldn't set for days or even longer. It might also wash away the first time the shower was used if it hadn't set properly. So with our unmodified thinset mortar, all of the water is used in the chemical reaction of hydration within the cement in the mortar.. Like concrete, the longer it stands the stronger the unmodified mortar bond gets..This process is used to bond the kerdi to the wall and the tile to the kerdi.
So why doesn't the mortar slide off the membrane? Remember the fleece? The mortar soaks into the fleece during installation, making a mechanical bond, not just a layer. My favorite analogy of this is in cooking. You're making a pancake, you put your batter in the pan and then put a washing up sponge in the pan too and make sure batter soaks in. When the pancake is ready, the sponge is going to be cooked into the pancake. There will be no separating it, the pancake will give first.. and so it is with the fleece membrane and the thinset mortar... The membrane is mechanically anchored.
We've been using Kerdi for several years now and have 100% satisfaction with the material. That means we've experienced a 100% rate of 100% waterproof in our shower assemblies. We are also confident in the fact that Schluter the manufacturer stands behind their products and contractors who correctly install the materials.
That's why MHS Works uses Kerdi, and why we recommend you specify Schluter systems in your next project. There is no one process in building a Kerdi shower stall that is hard, but like most things, it's harder to pull off well than it is to talk about it. There's lots of precise measuring, cutting and folding, a lot like origami. And like origami, we can all make a paper aeroplane, but about that swan?
Disclaimer. We are not a Schluter dealer. We not paid by them or their agents. We make no profit from exclusivity. We talk like we do because we believe in the manufacturer and their products