Installing a Preformed Shower Base: an Overview

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Introduction: 

During a major bathroom remodeling project, or when installing a new bathroom, installing a new preformed shower base is a common task. And as with any major fixture, choosing and installing a shower base takes some careful planning to make sure that everything fits and works well. As is true when buying a bathtub, you’ll need to make sure that you buy a shower base that will fit your space and work with the existing drain line. Shower bases can be ordered in many different sizes,...MORE with drain locations in different locations to match different circumstances.

To keep the number of drain adjustments to a minimum, try to match the new shower base to the current drain location. For example, if you are taking out a tub that has the drain on the right side, try to buy a shower base that has a right side drain, as well.

Also, if you are installing a shower as a replacement to a bathtub, keep in mind that the ideal drain size for a shower is 2" pipe, while most tubs are plumbed with 1 1/2" drains.  In this case, you will need to make some plumbing adjustments to increase the size of the drain.  One option is to bring a new 2" line over from the toilet drain line or the main drain line. If you can, avoid plumbing a shower with 1 1/2" drain pipe, because unlike a bathtub, which can hold much more water, a shower drain can be susceptible to overflowing if plumbed with 1 1/2" pipe rather than 2". 

Here is an overview of the steps for installing a typical preformed shower base.

  • 01 of 06

    Prepare the Space

    Remove everything and clean out space for the shower base. The walls need to be clear down to the studs. The floor needs to be as clean as possible so that you can level the base.

  • 02 of 06

    Dry-Fit the Shower Base

    Set the shower base into place to gauge what changes may need to be made to the drain. Take measurements from the back wall and sidewalls, and write them down so you can line the drain up.

    Now, with the shower base in position, check along the edge of the shower base to make sure it is sitting level Use shims and make marks on the studs to make it be easy to level the base when you put it back in.

    Put some cardboard in the shower base and walk around on it to see how stable the shower base is....MORE Most installers recommend putting a bed of mortar down for the shower base to sit into. Check the manufacturer’s installation instructions and see what they recommend, in case the use of mortar is discouraged.

  • 03 of 06

    Attach the Drain Fitting into the Shower Base

    Remove the base and install the shower drain fitting into the opening in the shower base. Apply plumber’s putty to the bottom of the flange on the drain fitting before installing it. Screw the drain fitting onto the base, and make sure that it is tight. In most cases, there is a large retaining nut that threads onto the tailpiece of the drain fitting that you tighten to secure the fitting. Make sure to install whatever gaskets or washers that are included with the drain kit.

    Depending on which...MORE shower drain you get, the 2" drain line may be designed to be glued onto the shower base drain fitting. In most installations, though, a compression-style drain is the easiest to install, because you can set the shower base over the drain, then tighten the drain tailpiece onto the drain pipe with a rubber washer and nut.

  • 04 of 06

    Re-check and Make Drain Adjustments

    Finish any drain adjustments needed to get the shower base to line up. When it seems right, it’s a good idea to drop the shower drain base into place again and make sure everything fits correctly before setting it the final time with mortar.

    Make sure the drain fits into to shower drain nice and straight and without stress on any parts to avoid fighting with it while tightening the shower drain.

    Continue to 5 of 6 below.
  • 05 of 06

    Lay Mortar Base

    Set some thin plastic down on the subfloor before laying the bed of mortar. Mix a bag a mortar and spread it over the area where the shower base will sit. The mortar should be about 1" inch thick. Stay away from the edges by a few inches to make the cleanup easier. The fins on the bottom of the shower base will embed in the mortar, creating a very rigid shower floor that won't flex when you walk on it. 

  • 06 of 06

    Set and Anchor the Base

    Set the shower base onto the mortar and level it carefully. Tighten the drain into place on the drain line. Test the drain by pouring water into the shower base. If you have access to the space below the shower, observe it from beneath the floor to check for leaks. 

    Some shower bases come with screws and brackets to attach the base to the wall studs. Otherwise, you can use screws with large heads, such as roofing nails, to attach the flanges on the shower base to the wall studs.

    Let the shower...MORE base sit overnight for the mortar to set up before stepping into the base any more.

    Now you are ready to install the wall surfaces and the faucet valve and showerhead in your shower. A good solution for shower walls is a surround kit