Do you prefer installing mud beds or pre-constructed shower kits when completing a new project or renovation? Are you aware of the pros and cons of each method? FCI spoke with a group of industry professionals about the topic. Panelists include Duane Farley, national sales manager and technical specialist, Canada, for M-D Pro; Sean Gerolimatos, technical director at Schluter-Systems; Mike Micalizzi, senior director of technical services for Custom Building Products; Michael Bobak, product manager at H.B. Fuller; Scott Crandall, director of national account sales and product management for USG Corp.; and Renee Robertson, national sales and marketing director, Fin Pan.
 

What are the advantages and disadvantages of laying a mud bed versus using a pre-constructed shower kit?

Robertson: Mud bed applications take an advanced skill set to build as well as taking more time to build, having a longer drying time and total time to finish the job. The pre-constructed systems allow for a less skilled installer to complete the work. When using a quick-dry modified thin set, the installer can be tiling within two hours and off the job on the same day.

Farley: The advantage of a mud bed is there are no restrictions to how small the tile can be as point load is not as much of an issue. The major disadvantages of a mud bed are the fact that mold and mildew can grow very easily, as the traditional mud bed installation holds in moisture. Mud bed showers are usually cold to stand on, they add a lot of extra weight to the subfloor, and when creating a mud bed, the slope must be exaggerated in order to make sure water does not collect elsewhere other than the drain location.
The great advantages of a pre-formed shower pan are that they are lightweight, easy-to-cut and handle, and the slope is perfect every time (usually 1/4 in. to 1/2 in. per foot). With the Prova system, you are not limited in the size or shape of shower base you can create when using the Prova Universal Extension Kit. Tile can be installed the same day, as you don’t have to wait a minimum of seven days for the mud bed to dry and cure. The entire installation takes a lot less time.

Gerolimatos: Shower kits, waterproofing systems and pre-formed components have advanced so much in recent years. Pre-formed shower trays made of polystyrene and other lightweight, stable materials are now available in many different shapes and sizes. They can be easily cut down or built up to suit the vast majority of situations, but there are still some applications where a traditional mud bed is advantageous, such as unique custom-shaped shower bases. A mud bed offers the maximum flexibility in design. While an installer may not encounter these situations often, the ability to mud a shower base is a great skill to have in his or her arsenal.

Micalizzi: The advantages of mud beds include material cost (sand, cement and latex additives); creating specific elevations and pitches for various tile sizes is much easier especially in a wet-set method; easier accommodation for large or unusual shower configurations; and liability issues—when a shower pan liner/drain is installed by a plumber, there is no liability for waterproofing for the installer.
The advantages of pre-constructed shower pans include labor, since shower pans are typically very lightweight and are less labor-intensive to fit into place compared to bags of sand and cement; required pitches to the drain are already achieved with the kit—no pre-pitch is required; and waterproofing is typically performed by the tile installer, not a plumber, which requires less scheduling and relying on other peoples’ work. The end result is more profit.

Bobak: Mud beds, although viewed as an “old school” application method, offer the end user versatility in customizing the size of the shower base and are traditionally a more cost-effective solution in materials. However, using a mud bed is usually a longer installation process than using pre-constructed kits. In addition, a higher skill level is needed to install a consistent and necessary slope towards the drain. Finally, a mud bed more easily allows for customization as opposed to a preform that must align with the existing shower and drain layout.

Crandall: The USG Durock Brand Shower System provides a customizable, waterproof, vapor-tight shower system that manages water and water vapor independently of the tile covering—unlike mud bed installations. The USG Durock Brand Shower System is also faster and easier to install than traditional mud bed shower construction.
 

What do professionals need to know in order to complete a mud bed installation?

Bobak: Achieving the proper slope is one of the most critical factors of the installation. Failure to do so could result in drainage-related failures over time. Additionally, installations using mud beds require the application of primary waterproofing membrane and can benefit from the application of a secondary waterproofing membrane. Membranes must be IAPMO-approved and meet ANSI A118.10 specifications.
For secondary waterproofing membranes, installation professionals have placed a great amount of trust in the performance of Tec Hydraflex, which offers waterproofing without the requirement of mesh and is part of a number of System Limited Lifetime Warranties for Waterproofing and Crack Isolation. If a secondary waterproofing membrane is used, it is critical to ensure the membrane is properly tied into the drain. Finally, before installing tile it is recommended that the system be tested for leaks.

Micalizzi: Installers need to know the substrate is sound, stable and not deflecting; that the drain is plumb and secure from movement; what the elevation of the tile surface will be and what tile is being installed, and whether it’s natural stone, porcelain or glass so they choose the correct mortar strengths, color and grout. Based on which tile and grout will be installed, an appropriate sealer and/or grout release may be chosen. On fast-track projects, a product like SpeedSlope Rapid-Setting Sloping Mortar can be used to reduce curing time to about an hour. The mud bed should always slope at least 1/4 in. per foot to the drain to prevent any standing water.

Gerolimatos: Here are a few points of importance to note. For applications over wood subfloors, begin by placing a cleavage membrane, such as 4-mil. polyethylene, to prevent the plywood from absorbing moisture from the mud before it has a chance to properly hydrate and gain strength. Galvanized metal lath is placed over the cleavage membrane and fastened to the plywood subfloor.
For concrete subfloors, the mud is bonded to the subfloor with thin-set mortar or cement paste. Mud, or dry pack mortar, is a mixture of clean sand, Portland cement and water. For a shower base, combine five parts sand to one part Portland cement. Begin adding water slowly and blend. Repeat this process until the mortar is damp enough to hold itself together when compressed in the hand but contains no excess water, similar to a sandcastle.
Pre-blended bags of sand and cement are available, but make sure to use suitable material. Concrete, masonry mortar and other bagged materials are not suitable and don’t lend themselves to the installation process.
A strip of mortar (screed) is placed, tamped and leveled around the perimeter of the shower base such that a minimum 1/4 in. per foot slope to the drain along all sides will be created. The remainder of the shower base is filled with dry pack mortar that is tamped and sloped using the perimeter screed and drain as guides. Typically, the mortar is left overnight to set up before the waterproofing membrane is applied.

Farley: The substrate must be clean and structurally sound. Proper mixing of the mud is essential—if it is mixed too wet, it will shrink and crack, and if mixed too dry it may not set hard enough. The installer will need to closely examine the waterproofing liner before it is installed. It needs to be checked for small pin holes, punctures or tears. Repairs must be done by a professional plumber before starting the mud bed installation.
If the shower is large and the waterproofing pan liner needs to be glued at the seams, one must take extra care when stepping or kneeling too far into the shower base area, as they could break the glue seal at the seams. With the standard size of pan liner that is offered in the marketplace, it limits you to the size and orientation of the shower base due to having to connect pan linear seams or outside corners together using the appropriate glue. The glue can fail in both bond and waterproofing if proper care is not taken. A sound check of the glue around all seams is a must. The installer will need to know what the minimum slope for water to drain is. It must be no less than 1/4 in. per foot.

Robertson: A typical mud bed installation requires training on how to properly perform the following steps: pre-slope the shower area, install a PVC rubber membrane without puncturing it, and properly mix and slope a mortar bed while paying special attention to not block weep-holes in the drain.

Crandall: Completing a properly constructed mud bed installation requires skill and time—more skill and time than would be required to install a pre-constructed shower kit.
 

What do professionals need to know in order to install a pre-constructed shower kit?

Gerolimatos: At the top of the list, it is essential to follow manufacturer directions carefully and not to mix components of different systems. Manufacturer educational workshops and Ceramic Tile Education Foundation (CTEF) programs can all help to improve the quality of results as well as the installer’s understanding of how all of the parts of a system work together. These systems reduce the time required to build a shower and they improve quality, but they still require attention to detail during the construction process.
Installers may want to look for systems that make it possible for the tile installer to complete all of the steps in the process. This gives the tile installer more control over the process and reduces crossover of trades on the jobsite, leading to a faster and better installation in the end.

Micalizzi: They need to know the area’s dimensions and precise drain location(s), the substrate requirements if installing over plywood or OSB, how to attach the pan to the substrate, how the drain will be connected, how to install appropriate waterproofing, and which mortars or adhesives are required to bond tile to the pan.

Farley: First, the floor must be level and if not it must be levelled before installing the pre-formed pan. The installer must know what kind of mortar is recommended by the manufacturer that will adhere to both the substrate and the pre-formed pan. The installer must follow appropriate waterproofing instructions by the manufacturer of the pre-formed pan so they know and understand how to connect the walls to the pan to prevent leaking.

Bobak: Although some manufacturers’ offerings can be adjusted on site, the installer should ensure that all measurements line up in order to ensure a proper fit and to be conscious of additional accessories needed in order to complete the job. When using kits, it is imperative to ensure that the space be square and plumb, and to follow all manufacturers’ recommendations. As with mud beds, before installing tile it is recommended that the system be tested for leaks.
Tec offers a comprehensive line of Preformed Shower Components that are easy-to-install and offer maximum protection with a Waterproofing and Crack Isolation System Limited Lifetime Warranty.

Robertson: They only need to know how to install the prefabricated shower pan to the subfloor according to the manufacturer’s specifications. Some prefabricated shower pans already have the drain in the base of the pan. This makes for a simple connection to the drain pipe stub in the floor. Other pan systems do require the installer to install the drain in the base of the pan. Most, if not all, prefabricated shower pan systems already have the proper 1/4 in. per ft. slope to the drain cut into the pan.
 

After finishing the installation, is there anything an installer should check over to ensure there won’t be any leaks or other issues?

Micalizzi: With either option, the pitch on the tile surface should be rechecked after tiling to ensure no birdbaths were created. Custom recommends following TCNA Detail B421 and applying the waterproofing membrane over the mortar bed to prevent saturation. A flood test should be completed after waterproofing and prior to tile installation.

Gerolimatos: The most important time to do this sort of jobsite check is right before the tiles are installed; once the tiles are on, it’s too late to correct any errors. Focus on all of the parts of the shower that are historically most vulnerable—around the curb, all corners in the shower area, valve and spout openings, and connections around niches and benches. Make sure that all manufacturer recommendations for sealing these areas have been followed properly and look for any gaps in waterproofing.
A water test is recommended, and may be required by building code officials on some projects before setting tile to verify a successful waterproofing installation. Insert a test plug in the drain or waste line and fill the shower base with water. The water level should be high enough such that the membrane-to-drain connection and floor-to-wall transitions are evaluated. Place a mark on the wall indicating the depth of water and after 24 hours check the water level to make sure there are no leaks.

Crandall: USG recommends using a water test plug and filling the shower with approximately 3 in. (76 mm) of water. After 24 hours, check for leakage and remove the plug. This confirms the waterproofing is sound.

Bobak: All installation should pass a flood test before being placed into service. Additionally, the installer should ensure that all weep holes are cleared of all and any remaining debris.