With the rise in popularity of linear drains and curbless/barrier-free showers, we asked shower installation products manufacturers to weigh in on what these trends means for installers and the best way to install these systems—which can be much more complicated than they first appear. We also asked these manufacturers to share some of their latest technologies and products.

Our panelists this month are Mark Pennine, Ardex’s tile technical manager; Francisco Ferrandiz, Guru USA’s director of technical services; Arthur Mintie, Laticrete’s senior director of technical services; Holden Wheeler, MAPEI’s technical services lead for their tile & stone installation systems; Josef Erlebach, head of technical support for Rapid Recess; and Sean Gerolimatos, director of research and development for Schluter Systems.

Linear drains and curbless showers are becoming more popular. What unique installation challenges do these trends create?

Wheeler: “In my opinion, the biggest installation challenges with linear drains and curbless shower receptors are actually the installations themselves. Not many installers up until recently had much (if any) experience installing linear drains or designing and building curbless shower assemblies.

“Sure, these methods and materials have been around for years, but now that they have become more commonplace, many more installers are venturing outside their comfort zone to get the job done. This is not necessarily a bad thing, but if an installer cannot get proper training and education before the job starts, they are going to have a serious learning curve on the jobsite.

“With linear drain applications, you have to slope the shower differently, tie into the drain differently, and in some cases use a specific type of waterproofing product that is designed or recommended in conjunction with the particular drain being used.

“With curbless showers, you can’t just use any waterproofing membrane, and not every bathroom is going to be configured for these types of assemblies, which can sometimes lead to frustration at the jobsite. The big takeaway with these sorts of projects is to plan, plan, and plan some more before the materials are even ordered. If you know what you are installing, where to install it, and how to install it well in advance, this will greatly limit the jobsite surprises.”

Gerolimatos: “Linear drains are unique in that the surrounding floor is sloped on a single plane instead of to a single point. It’s important to consider the shower dimensions as they relate to the length of the drain; will the drain extend from wall-to-wall or will it have tiles installed on either end as well? Linear drains that are installed directly against a wall can also present waterproofing challenges. One option that can mitigate this is to use a drain with the waterproofing membrane already attached. Many of the challenges associated with linear drains can also be avoided with proper planning.

“With linear drain applications, you have to slope the shower differently, tie into the drain differently, and in some cases use a specific type of waterproofing product that is designed or recommended in conjunction with the particular drain being used.”

– Holden Wheeler

“Curbless showers are unique in that they rely on the slope of the floor to effectively contain water in the immediate shower area and direct water to the drain. Prior to installing a sloped mortar bed or prefabricated shower tray, the floor must be recessed to allow an even transition at the door threshold. This may be a straightforward task in new construction, but can be challenging in renovations. Any recessing of the subfloor must be done in a way that preserves the structural integrity of the construction.

“If recessing the floor is not an option, Schluter Kerdi-Shower prefabricated trays with a ramp can be utilized in such applications. Curbless showers require waterproofing in all areas subject to water exposure. Ideally the entire floor is protected, with secondary drainage installed in the drying area for any overflow. The Schluter Shower System provides a simple and effective means of waterproofing curbless applications.”

Erlebach: “There are two different types of linear drain installations: over plywood floors, where the drain can be recessed between the floor joists using our Rapid Recess brackets; and over concrete floors, where the drain gets installed at the entry of the shower but has to span the full width of the shower.

“The challenges are that most of the linear drains are not really ‘drains’ but just covers for standard point drains and thus requiring a lot of depth for installation—so they are not really suitable for those curbless shower installations where you want almost no depth. There is also the challenge of being able to make the drains on-site to fit any opening perfectly with no spaces on the side of the drains where water can run freely out of the shower.”

Mintie: “A linear drain that is located off to one side is more highly recommended than drains located in the center of the shower because it requires only a single slope, making it easier to install with a pre-sloped shower pan. This design is also more aesthetically pleasing, thanks to its ability to act as a base for large-format tiles and other grand designs that would otherwise be limited to small tiles because of the curvature.”

Pennine: “One of the main challenges when installing a curbless shower is to create sufficient slope in the shower area when dealing with an existing wood subfloor and joist system. The size of the shower and the amount of slope needed often forces the installer to look at all possibilities. Do you try lowering the floor of the shower area between the joists? Can you raise the outside floor? Or is a combination of both the best solution? Sometimes, a pre-sloped shower pan is a great timesaving option to consider.”

Ferrandiz: “The biggest challenge for curbless showers is the height of the shower base installation. Building codes require shower pans to slope down to the drain 1/4 in. per ft. at least, so that the higher the drain and the larger the shower, the greater the height at the shower perimeter. A recess in the floor is usually needed to compensate for the height of the installation, and it is a big limitation—especially when remodeling on wooden subfloors where it is barely possible to obtain 1 to 1 1/2 in. of total height with the recess. The best solution is a system with a pre-sloped base offering a low height, along with a low-profile linear drain.”

What should an installer know when waterproofing a shower? How do you ensure that the waterproofing gets all the way around a linear drain when the drain is very close to the edge of the wall?

Pennine: “Waterproofing is an installation process that has to be planned in advance. All the changes of planes, corners, pipes, niches and the drain tie-in should be addressed first. When a linear drain is going to be installed close to the wall, the reinforcing mesh should be cut to size before setting the drain. When using a liquid-applied waterproofing product, a paint brush is the best tool for coating against drains and wall tie-ins. Be sure to apply enough material (to the required mil thickness) as stipulated by the manufacturer for waterproofing.”

Mintie: “Because barrier-free bathrooms do not confine moisture to the shower alone, it can be difficult to separate the wet area from the dry area. As such, the bathroom must be sufficiently protected against water and moisture as a whole. Installers should use either a liquid waterproofing membrane or a sheet membrane, which both result in the same protection while utilizing different methods.

“For installers who prefer to use a liquid waterproofing membrane, it is vital to apply the required number of coats and mils—which measures thickness—to prevent failure. This number varies depending on product and manufacturer. To help measure how many mils thick a liquid membrane is for a guaranteed successful installation, there are many wet film gauges available on the market. Another consideration if choosing to use a liquid waterproofing membrane is the cure time. Cure times can vary by manufacturer and are influenced by project site conditions.

“To ensure waterproofing gets all the way around a linear drain when it is close to the edge of a wall, installers should consult with the membrane and linear drain manufacturer on how to handle the installation. Typically, the membrane will have to tie into the drain’s bonding flange and then turn up the wall to create a seamless and continuous pan effect.”

Wheeler: “Continuous is a word I like to use when talking about waterproofing. If the membrane is continuous, across the entire pan, and all the way up the wall, it will have no voids, penetrations, pinholes, etc. All of this means water will have no path through it and into the materials behind the waterproofing membrane. If you are going into showers and waterproofing only the cement board seams, or stop the waterproofing at the wall without coving up, that is not continuous.

“Most linear drains will have some sort of material around the edges that interfaces with the waterproofing membrane chosen. This makes life easy for the tile installer, because he or she can tie it right in with the desired waterproofing membrane. Some drains don’t have this feature, and it is very important to plan out the shower and dry-fit all the materials before starting.

“If you dry-fit the drain assembly and the back of the drain is hitting the wall, it’s time to have the plumber back out to help move the drain forward a bit. Unless the drain is specifically designed to hug the wall somehow, there should be enough room behind and on the sides of the drain to waterproof all around it, continuously.”

Ferrandiz: “There are two ways to connect waterproofing to the drainage. Some linear drains have a built-in bonding flange with which to connect the waterproofing, and it requires a careful installation. The other way is to use a common clamping ring-type subdrain (probably already installed) to connect the waterproofing beneath the linear drain and extending up the walls, as in the Guru Evolux system. This will create much less risk of leaks.”

Erlebach: “The old PVC or CPE liners will not work for these types of installations. The market is divided along the lines of topical sheet or topical liquid waterproofing as the best approach.

“Laticrete and Custom Building Products came out with their fast-curing, liquid-applied waterproofing and this will change the game since the need to wait for a second coat overnight does not apply any longer. Thinner and higher-density shower pans with better compressive strengths are also being used, such as the ones by M-D Pro.

“Prior to any waterproofing taking place, the installer should note areas prone to potential leakage ... and address these areas accordingly.”

– Sean Gerolimatos

“Obviously a great solution when installing a curbless shower pan on a plywood floor is our Rapid Recess kits. The biggest challenge we see in curbless showers is the understanding of the capillarity break. Capillarity is when a liquid inside a capillary or absorbent material rises or falls with surface tension. This separates the dry from the wet under the tile so that no water will wick through the installation. Now, there might be very little water going out that way—but it can be also be a lot of water. That is one thing that very few installers or even architects understand, and we are fighting it every day.”

Gerolimatos: “Arguably the most important part of waterproofing a shower is to decide on a complete system approach. Assembling components from various manufacturers or methods is ill-advised as it brings higher risks of incompatibility, leaks and lack of warranty coverage. Prior to any waterproofing taking place, the installer should note areas prone to potential leakage (such as inside/outside corners, curbs and benches) and address these areas accordingly. Schluter Systems offers prefabricated Kerdi accessories as suitable waterproofing solutions for these mentioned areas.

“Waterproofing around a linear drain with close proximity to a neighboring wall is a challenge in itself. Schluter-Kerdi-Line drains feature a factory-applied Kerdi waterproofing membrane collar that can easily be folded and adhered to the adjacent wall. This helps keep this part of the installation simple and easy and ensures continuous waterproofing throughout the shower area.”

What are some of your latest waterproofing and installation accessories for showers?

Ardex: “Some of Ardex’s waterproofing and installation accessories for showers include pipe collars, mixing valve collars, inside and outside corners, pre-formed curbs and pans.”

Custom Building Products: “A high-performance, fast-track product, Custom Building Products’ RedGard SpeedCoat allows installers to float a mud bed, waterproof, flood test and set tile in hours rather than days—even in challenging cold or high-humidity environments. RedGard SpeedCoat provides installers with a ready-to-use, liquid-applied waterproofing barrier that cures quickly, consistently and effectively in extreme conditions over concrete, cement mortar, cement backerboard and masonry.

“Additionally our SpeedSlope Rapid Setting Sloping Mortar is a rapid-setting, rapid-hardening, polymer-modified, pre-blended, cement-based mortar bed and sloping mortar for leveling and ramping up to 3 in. on horizontal substrates and 5 in. in confined areas like trenches. SpeedSlope is ideal for shower installations. Setting in one to two hours, SpeedSlope is also a perfect surface preparation choice for additional applications including patches, ramps, floors and walls.”

Guru USA: “The unique installation challenge for a renovation project involving a curbless shower is how to absorb the height of the shower underlayment, slope or pan in such a way that there is no curb or threshold where the shower floor meets the bathroom floor. The easiest way to address this is to recess the subfloor using a product like Rapid Recess and then installing a low-profile shower pan and drain system that is strong enough to sustain the loads. The Guru USA Evo Slant system and Evolux drains offer the lowest profiles in the industry, and are perfect for curbless systems,” stated Derick Cooper, Guru’s national sales and marketing manager, North America.

Laticrete: “We recently launched Hydro Ban Quick Cure, a liquid-applied, ready-to-use waterproofing membrane; and Quick Cure Mortar Bed, a pre-mixed, polymer-fortified thick bed mortar, to provide the industry’s fastest mortar bed shower system installation. Using Hydro Ban Quick Cure and Quick Cure Mortar Bed in conjunction allows for following trades to begin tiling within hours.

“Hydro Ban Quick Cure is available in a 1 gallon (3.8 liter) pail and Quick Cure Mortar Bed is available in a 60 pound (27.3 kilogram) bag. Both Hydro Ban Quick Cure and Quick Cure Mortar Bed are eco-friendly, emitting low VOC, and are components of the Laticrete Lifetime System Warranty providing peace of mind for trouble-free installations.

“Most recently, to accommodate virtually any shower installation, Laticrete launched a series of new and improved grates and troughs in a variety of sizes and finishes, with custom sizes available upon request. The new options are part of the Hydro Ban pre-formed shower system that includes an expansive line of pre-sloped and linear shower pans, niches, seats and benches made with a high-density polystyrene core, and installation accessories like liquid-applied and sheet membranes, sealants and lightweight ready-to-tile wallboard backed by the industry’s best warranty.”

MAPEI: “Our newest waterproofing product is Mapeguard WP 200. This product is a thin, flexible polyethylene sheet membrane with a nonwoven, polypropylene fabric on both sides that functions as a waterproofing membrane as well as a crack isolation membrane. Mapeguard WP 200 is adhered to the walls and/or floors of the shower with a polymer-modified mortar, and tile can be set immediately after. This product comes with a variety of accessories to be used in conjunction with it, such as pre-formed inside and outside corners, and pre-formed pipe penetration rings.”

Schluter: “Schluter Kerdi is now available in a 2m (6’7”) wide roll to cover the wall area from the floor to the standard shower head height, allowing installers to waterproof shower walls seamlessly. Several new drain grates have been released under the Style offering for both Kerdi-Drain and Kerdi-Line, with new colors and finishes on the way soon. Inspired by the design of Style drain grates, the Schluter-Shelf makes the installation of shower shelves easier than ever in both new and retrofit applications.”