Understanding Shower Pan Membranes and Their Role in Waterproofing

The importance of have a properly installed Shower membrane is often one of the things that is least considered when designing the bathroom in any project. Here are a few of the facts that will help you in understanding shower pan membranes and their role in waterproofing.

• An average 10-minute shower using a single showerhead, uses 25 gallons of water! Even with the low flow technology being used today.
• Up to 15% of the amount of water used during a shower, depending on the type of the materials used, can penetrate the hard surfaces and grout lines of your shower floors and walls. This water migrates to the shower pan membrane which prevents any water intrusion to the area outside of the shower.
• A properly pitched shower pan membrane needs a minimum of a quarter inch to a half inch maximum per foot slope or “pitch” to the drain weep holes with no areas that form puddles larger than 1 inch round.
• Weep holes need to be cleaned and protected from debris that can inhibit their purpose and function within the shower pan membrane. An often-overlooked procedure after the shower pan membrane is installed.

Shower Pan Membrane Facts

Many areas in the construction housing industry need waterproofing. Basements, walls, and roofs are what 1st come to mind. All keeping the water from entering the house from the outside in. Detailed attention is given to the quality of product and the proper application procedure needed to ensure the best protection against water intrusion. Our showers are no different, a high volume of water being sprayed in an enclosed area in which we don’t want it to do anything more that ends up in the drain and not entering any other area of our home!

With many types of shower pan membrane systems available they all can serve the as the most important part of keeping the water in the drainage system and not leaking into the finished areas of your bathroom. Picking the one that fills the parameters for your particular project is sometimes an overlooked detail that can give you an inferior job due to the cost to the contractor. Some methods will work better than others depending on the design of your shower.

The Basics for All Shower Pan Membranes

All shower pan membranes will have a number of “must have” in common for proper installation and to give the best protection.

• Solid backing is needed around the perimeter of the shower at the minimum of 10 inches off the subfloor.
• A 2 inches-two-piece clamping style drain, or an approved drain supplied by the manufacture of a non-weep hole shower pan membrane system.
• A solid base that is a minimum of 1 inch per foot sloped from the farthest point in the shower to the drain.
• No ponds or ripples larger than code requirements to inhibit the flow of water to the weep holes
• No staples or nails within 2 inches from the top of the curb finish around the full perimeter of the shower after the membrances installation.

Damages Caused Be the Incorrect Installation of the a Shower Pan Membrane

• Leaving gaps in the backing can cause a tear or a puncture when the hard finish base is applied over the studs. Be it paper and wire with mud set, or sheet goods of all types. A slight miss with a stapler, a hammer blow, or slipping off a screw head, can and will cause a puncture in the membrane. Causing an area of weakness which if not addressed will give a place for water to accumulate and work its way through gradually enlarging the hole and letting more and more water to the unprotected areas behind your shower walls, which will build up over time and damage framing, porous subfloors, (plywood and OSB board) and give a chance for mold to grow. This can take up to a year or longer for the damage to be visible usually showing up with damage to the baseboard and drywall. This long-term slow damage when finally discovered has created a situation that may require a total rebuild of the shower.
• The importance of using the proper drain for the shower pan membrane is paramount. Certain drain styles may require specific drains for that product.
• The pre pitch cannot be overemphasized, it serves as the “flow chart” for the water that penetrates the shower surfaces and makes it to the shower pan membrane. “Water in water out” excess water that cannot flow to the weep holes due to a lower than required “pitch” will remain in the dry pack, this will over saturate the dry pack base, causing the wicking effect and water can travel up and out of the shower, typically at the shower pan curb or recess. This can also cause tile, stone, grout discoloration, and also a chance for mold.
• This goes hand in hand with having the right pitch in the shower pan membrane. Any obstructions or ponds that will retain water can also cause the problems mentioned above.
• This is one of the most prevalent causes of shower pan membranes leaks. Nails and screws dropped in the pan by other trades doing their work and embedded into the membrane. Workers using buckets or ladders to stand on in the shower without protecting the shower pan. Stapling, screwing, nailing into the membrane to attach backer material for the hard surfaces of the shower. This is one of the most common mistakes. This too is a problem that take a while to show itself, as the water will slowly rust the fastener over a matter of weeks and months until water can pass through the membrane, over time more and more is able to pass through that can cause any number of issues as stated earlier.

In Conclusion

Your shower is like the rain forest! Water, mist and steam everywhere! With your shower walls, glass, and floor sending most out the drain. With the amount of water used in your shower some will not get to the drain fast enough and will be soaked into the surfaces of your shower to reach the shower pan membrane. The last defense against water intrusion that will damage your home! The shower pan membrane plays a key role in long term protection.