Many manufacturers of liquid waterproofing products offer reinforcement materials for all corners and for drains in shower applications. Almost universally pre-treatment of those areas are required for effective waterproofing.


New home construction has slowed down substantially in most parts of the United States. With it has gone some of the easy money many have enjoyed for years by just doing floor work. But, a good number of installers have continued to enjoy a healthy backlog of jobs just waiting for their talents. Why do some seem so busy and others are starving? In many instances, it is their higher skill level and ability to do jobs beyond the ordinary floor or backsplash installation. True today as it always has been since I been in the trade, a good floor tile installer does not make a good shower installer. Retailers seem to have a hard time grasping this concept. They assume because the installers work always looks great on the floor he certainly could do the same with a shower or tub. Installers know better, many cringe at the idea of having to enter such a foreign realm with the very high stakes liability that water damage in someone’s home brings. Floor and wall tile installation require a certain amount of skill and some very basic knowledge. Showers and wet areas on the other hand require a high degree of both skill and knowledge, more so when mortar shower bases are used. This is typically where things can go bad for a good floor installer. With the proliferation of products being offered today, it can go from bad to worse particularly in the area of product knowledge on installation requirements. There are many fine and viable products being offered but often there is little information readily (keyword) available other than the typical sales pitch. Showers being constructed today are increasingly complex and with them the inherent risk of water damage increases. While this can easily turn into a book, let’s take a short look at some of the basics in shower building 101.

Building a curb properly out of mortar is a time consuming task. Pouring a curb of concrete provides waterproofing issues. Nailing backer board into the curb makes for leaks and requires additional waterproofing. Manufacturers have come up with numerous products to make curb building simple; some are displayed here.

All water must go down the drain. Sounds exceptionally simple doesn’t it? I think so too but if I were a betting man, odds are there is a lot of money to be made saying it doesn’t always work that way, some would go so far as to say seldom. All too often water is left behind in the shower assembly courtesy of not just the tile installer but the plumber, and in some local jurisdictions (I hope they are reading this) code officials. Showers are water management systems. The typical shower sees more water in a month’s use than many climates receive in a year. To effectively manage this staggering amount of water, we need a number of things to happen. First and foremost should be the proper pitch under the waterproofing material. Most state and local codes are adapted from one of several national code writing organizations. All of these organizations require that a pre-pitch of ¼” per foot be used under the waterproofing material. This is probably the least enforced plumbing code item in the book. Given the time and money it takes to create a pitch, coupled with lack of enforcement by code officials, plumbers commonly ignore this code requirement when they install shower pan liners. Where tile installers are allowed to install the waterproofing material, code applies to their work as well. Assuming this requirement is met we must have a proper type drain assembly for this pre-pitch to be of any benefit.

Common floor drains are not impossible to fit with an effective seal at the drain where surface waterproofing is required but are very difficult and require exacting methods with 0 margin of error. Showers installed over on-grade concrete floor drains should be waterproofed.

Conventional shower drains for mortar applications actually have two drainage areas, the top which we are all familiar with and weep holes at the bottom where the membrane clamps or is fitted to the drain assembly. These holes must be kept clear of mortar to function properly. There are numerable ways to accomplish this. You may surround the weep holes with spacers, broken tile bits, or use a manufactured product such a plastic or spun nylon weep protector. While it may seem the water would pass through mortar, which it does, it is not fast enough to allow for the mortar floor to ever fully drain. The organic matter in the water can and will eventually breakdown the cement mortar where prolonged contaminated water saturation occurs. In the case of large showers you may want to consider the use of a drainage mat over the top of the waterproof membrane. Even with the proper pitch and weep holes being kept accessible for drainage there is a very large amount of water kept in the shower floor seeking a way out of the floor. This water must wick its way from the outside edge to where the drain is located. This is often only a few feet but in larger showers can become much more. Drainage mats provide a path for the water to freely leave the systems soon as it passes through the depth of the mortar bed, a few inches, instead of feet. This promotes a healthier environment not only for the mortar floor but the bathroom itself by reducing the amount of humidity caused by the water otherwise slowly draining from the floor. I think most of us have been in commercial environments where you could feel the humidity of large water exposed areas and showers. Using a drainage mat would be a great contribution to reducing that damp feeling.

Once we have provided for the proper drainage we need to select the appropriate waterproofing material. There is a proliferation of waterproofing products on the market today. Years ago we used lead and cooper sheets. These sheets were then seamed together with molten metal. History has taught us that when properly done those systems can provide many years of service. There is one draw back however, the days of those systems are numbered by the interaction of the wet mortar to the metal which causes metal degradation to failure at a rate dependant on both pitch of the installation and the installation itself. In some areas of the country there is a system called hot mop. This is a highly regionalized method using hot tar and roofing felt in multiple layers. Then we have the next generation of materials which are sheets of either a PVC or CPE product. These come in varying widths and typically with accessory items such as pre made inside and/or outside corners, adhesives for seaming, and sealants for use where penetrations are present. It is always preferable to use as large a sheet as reasonably possible. Why make a seam and assume any risk if not necessary? If you’re local supplier does not carry a complete line of products with all these items it would be wise to consider special ordering the materials you most commonly use and stocking them yourself. We found this to be the case especially with the larger 6’ sheets and outside corners in our particular area.

Traditionally a layer of tar paper, some metal lath, and mortar are used to pre-pitch a shower pan. This is simple and inexpensive but unless there is additional work in the house you have to wait till the next day to install the shower pan material. There are several pre-made products on the market that allow work to continue.

Some of the more popular products of today are topically applied waterproofing products. These come in various forms such as liquid, cementious, and sheets. These products are applied directly to the surface to be tiled. The rapid development of these products has been both a blessing and a curse. The blessing is it only makes sense to waterproof the surface and prevent any water from entering the building envelope at the point of entry. They make waterproofing seats, knee walls, curbs, and niches much easier than waterproofing under them and avoid nail penetrations entirely. They prevent the walls and floors as well as their support structure from holding any substantial moisture resulting in a dryer and healthier environment. The curse is they are widely misused, abused, and not thoroughly understood. The sheet type products in this category are not quite as subject to miss use as the liquids and trowel on products. If the sheets are not properly seamed and bonded they result in leaks which are relatively easy to detect. However, liquid systems when not properly installed result in weeping, not leaking. By the time a weeping issue is discovered the damage is quite substantial. It is much easier to see and stop running water than a very high fog like humidity. The degree of waterproofing provided by liquid and cementious systems is entirely dependant on what is know as film thickness. With trowel-on systems the trowel itself is used as a metering device to assure proper thickness. Typically the product is keyed into the substrate with the flat side of the trowel, combed with the notch side of the trowel and then the ridges are flattened by combing once again with the flat side of the trowel. If you’re good with a trowel and have a smooth surface this is a relatively simple task. Liquid systems a little trickier, most require multiple coats not so they can sell more product, as some would believe, but because it takes a specific thickness of the product to be waterproof. Think of a raw wood board and the first coat of paint. It readily soaks into the wood. You know if you don’t put another coat on and it is exposed to moisture it will rot. That is the same effect an inadequate film thickness has when liquids are used as a waterproofing material.

Shower drains for mortar applications require a specific type of drain to allow for water to pass through the floor mortar and down the drainpipe. This drainage is provided by small weep holes at the lower part of the drain.

Another key issue on making these latest generation products work is the drain interface and corner reinforcement. This is most often where installation issues arise. There is one manufacturer on the market who makes both a drain and a waterproofing product so you have a complete systems approach, most do not. Several systems are available with a special drain flashing. Product availability varies, these pieces are not always easy to find. Check with your selected manufacturer for a full line of their products, you may be surprised at some of the work saving materials available. Your supplier will be happy to stock them if they know they will be sold. With liquid systems, most provide detailed instructions on how to attach or bond their product to typical two-part shower drains widely used by plumbers. Most often these recommendations involve the use a fabric or fiberglass reinforcing material at the flange prior to bolting in the top of the drain assembly. When these types of systems are used the drain pipe must be firmly anchored to the framing below, not by the waterproofing. Most liquid or trowel applied products also require reinforcing fabric or wide sheets of fiberglass tape be used at all changes of plane. These areas are typically pre-treated prior to the field application of product. Inside and outside corners are a critical application and have their own requirements in addition to and not covered by the change of plane pre-treatment.

The best idea and typically a requirement when using any direct bond waterproofing application is to treat the entire shower to prevent any water that may be absorbed by the wall backing surface. More often than we care to see, we receive pictures of showers that have had partial waterproofing or inadequate film thickness and have failed. With few exceptions, backer boards are not waterproof. Those that are still have special requirements for fasteners and edges to effect true waterproofing. Because many backer boards do allow either water or vapor to pass, most recommend the use of a vapor membrane behind their panel in tub and shower applications but may be omitted when the entire unit is waterproofed. Building codes vary on this requirement and always prevail over manufacturer recommendations. In the case of showers where no surface waterproofing is present, a vapor membrane should extend a minimum of two inches over the top of a conventional shower pan liner system.

While we have spent a great deal of time on the floor getting the water from the walls and floor down the drain and preventing damage that will otherwise occur, we should pay due attention to other areas of the shower. When most plumbing codes were written, and government bodies being what they are, no consideration was given to seats, niches, and knee walls. Curbs also remain an item of mystery for many. All of these surfaces must have a pitch to direct the water to the floor drain. They must all be waterproofed as well. The new TCA Handbook for 2007 has added language to reflect this need and perhaps some day code will also reflect this issue more appropriately. The failures of seats in particular are rampant.

There is currently only one drain made for direct bonding of waterproofing materials in showers and it is part of a proprietary system. It is placed in the top of the mortar bed. Others can be adapted but each manufacturer has their own preferences and instructions for effectively sealing the shower drain. There is no universal or industry method, each is manufacturer specific.

While we have been focusing on conventional showers, much of this also applies to steam showers but they are separate and present another series of other requirements. The selection of a waterproofing product for steam showers must be given special consideration. There are many products that meet industry standards for waterproofing, ANSI A118.10, and are approved by various code organizations, but will not perform in some steam shower applications. The industry standards apply to waterproofing products but steam is a gas, not a liquid. Because something is waterproof does not make it vapor proof. Think of a household drain pipe, we run thousands of gallons of water down the pipe with no leaks. However, what would happen if we used a waste pipe for our gas piping? Not to difficult to figure the result, it would be catastrophic. For steam we need to consider vapor ratings which are known as perms, the higher the perm rating, the less vapor proof. There have been many instances where a liquid or trowel on waterproofing product has been used in a steam shower and resulted in very costly repairs. Make sure the product you use is rated for steam applications based on the environment it will be used in. Residential steam showers are somewhat of a novelty item and not used daily. If they are in daily use, you should use commercially rated products which will limit your selection of materials. Steam showers need pitched ceilings so the water does not drop on the occupants. All penetrations in steam showers must be sealed to prevent costly damage. Recently we have been receiving an over abundance of failed showers and steam showers pictures recently and the damages in some instances are more than I will make in a lifetime so be careful out there.