How To Build Your Own Shower Pan

This article gives step by step instructions for building your own shower pan, including measuring slope and drain assembly.

Building your own shower pan is a good alternative to installing a prefabricated shower, especially if you are working with a small space, or you are trying to achieve a certain style. The installation is not difficult if you understand all the steps and the purpose behind them. If you pay attention to details and complete each step thoroughly, there should be no reason for your shower pan to fail.

The first step is to ensure that the floor you will be building on can support the weight of the shower. Take into consideration that you will be building the first layers with cement, so the floor will be very heavy. You may need to (and probably should) reinforce the sub floor with exterior grade plywood to add an extra layer of strength. Also examine the joists under the floor, particularly if you are working in an old house; they may need to be reinforced.

The simplest method of building a dam for the shower is with 2x4s. Nail 3 to 6 boards (depending on how high the dam should be) to the floor. Make sure to toenail the ends of the boards to the studs in the wall. Continue nailing the boards on top of one another until you have achieved the desired height. Once the dam is secured, you need to focus on the first part of the drain. You will need a two-piece drain. One piece will rest on the floor and connect to the drainage pipes under the floor. The second piece will go on top of the first layer of cement and the liner, which will be discussed in more detail later. Install the drain using PVC cement, or PVC connectors if your pipes are not PVC. Follow the instructions on the container for using PVC cement to connect the drain to the pipe. Make sure that the drain sits levelly on the floor and fits snuggly on top of the drainpipe.

After waiting the required amount of time for the PVC cement to set, you will need to build the pre-slope. Start by measuring from the center of the drain to each wall. The slope should be at least ¼ inch for each foot. For example, if the back wall of the shower is 3 feet from the drain, the slope will need to rise to ¾ inch at the wall. Draw a guideline all the way around the shower and double-check your measurements. Also, if your drain does not fit flush on the floor, you will need to take that into account when measuring the slope. The next layer will need to be packed under the rim of the drain so that it fits flush. Simply measure the space between the floor and the rim of the drain (about an inch or so) and add that to your slope figures. This will ensure that you build the floor up to the level of the drain and maintain a good slope. A poor slope will cause water to stand in the finished shower and eventually seep through to the floor. Drainage is one of the two most important issues in building a shower pan. You want the water to run effortlessly to the drain, and an adequate slope will achieve that.

With your slope guidelines in place, you are ready to build the first layer of your shower pan. Put a layer of dry set mortar mixed with a latex additive on top of the floor. The latex additive makes the mortar more water resistant, and the cement will adhere better to it than the wood. Use a mixture of 1 part Portland cement and 3 parts sand mixed with water to the consistency of mud to build your slope. You want to be able to pick up handfuls of cement, not pour it. Pack the cement mud into the shower floor building up to the slope lines. This layer should not cover the drain; the rim of the drain should rest on the floor or on top of this layer of cement mud. It is a good idea to place a rubber stopper in the drain before beginning the cement process, and screw the screws into the holes so that they are not accidentally filled with cement. Work the cement mud with a trowel until it is smooth and level. Let this layer set overnight.

The next step is the shower pan liner. This is the waterproof layer that will allow any water that may seep through the floor to drain without ruining the floor underneath the shower. PVC shower pan liner can be found in your hardware store, and it usually comes in a big roll and is cut to the size you need. You will need to cover the entire floor and a minimum of three inches around the shower walls. It is important that you cover the bottom few inches of the walls to prevent water from seeping under the liner. Note: the liner should be one solid piece. Be careful when handling it because a puncture would defeat the entire purpose of the liner. Lay the liner out in the shower floor and arrange it so it is flat on the floor and fits snuggly. At this point you will need to use a sharp utility knife to cut around the drain. Very carefully cut an X on top of each screw, always cutting toward the drain. From screw to screw, cut around the inner edge of the drain until you have formed the drain opening. Use shower pan liner adhesive to glue the liner around the drain; put adhesive on the liner and on the drain and let is set a few minutes before continuing to glue the liner. Use the same adhesive to glue the liner to the cement and around the walls. Connect the second piece of the drain to the first with the screws provided. The drain grate, the part that will show in your finished shower, should be adjustable. Fix it to your desired height and remove the screw-on cover so that it does not get dirty in the final stages of construction. Allow the liner to set overnight. At this point you will finish installing your shower wall surround or cement backer board (for ceramic tile). Do not use screws below the level of the dam or at the level of the PVC liner; screws at this level may cause leaks.

For the next step you will need to draw the slope guidelines again, following the same rules. Pile pebble sized gravel around the drain to keep the weep holes open during cementing. The weep holes are essential for allowing moisture to escape if it should seep through the shower floor. Again you will use a 1 to 3 mixture of Portland cement and sand, also to the consistency of mud. Pack it into the pan on top of the liner, being careful to maintain the slope. (You will know that your weep holes work because the water from the cement will weep into the drain as you work.) This is the foundation for the finishing layer of tile, so you want it to be smooth, level, and well sloped. Leave about a ¼ inch between the top of the drain and the cement; this allows the tile to be level with the finished drain. Allow this layer of cement to set overnight, and then you are ready to tile the shower floor. Screw on the drain cover once you have finished the tile job. The final step in a good shower pan is to seal the grout in your ceramic tile. Sealing with at least two coats will help repel water that would otherwise be absorbed into the shower floor and cause problems with your shower pan.

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