A shower base is a single-piece pan fitting underneath the shower walls. Designed to drain water from the shower, it protects your floor from water intrusion, rot and mold. Installing one requires some skill and there are certain rules and procedures to follow when doing so. In some cases a mortar bed is a necessity; other times it isn't.
A shower base may seem simple, and it is, but it must be installed properly in order to work. Since the shower base is designed to drain water from a shower faucet, it has a slope already built in. This slope drains water towards the drain hole, allowing proper drainage under normal showering conditions. However, since there is a slope built into the base, the base needs to be level in order to take advantage of this slope. This is the main consideration when deciding on whether to use a mortar base or not.
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Unlevel Playing Fields
If the shower base installation floor is not level, there are two options. The first is to slide shims under the base to bring one or more sides up to level. The second is to add mortar to the floor to even it out. If sliding shims under the base does not work, opt to install the mortar bed. This is usually a good idea when floors are badly sloped or the use of shims is simply not practical. If the shower base has large gaps underneath it due to the use of shims, the base will stress as someone walks over them during showering.
Installing a Mortar Base
To install a mortar base, mix the mortar in a large, five gallon bucket with water. Use a trowel or cement mixer to properly mix the mortar and keep it soft until you are ready to spread it. Install a drain dam inside the drain pipe or drain hole to prevent mortar from falling through it. To apply the mortar bed, spread it evenly around the shower area. The idea is to create a flat surface for the shower base to lay on. Allow the mortar bed to dry completely and cure before installing the shower base. This is usually 24 to 48 hours.
There are other options besides installing a mortar bed. If you decide not to install a mortar bed alternatives include installing another layer of sub flooring, or cement backer board. Leveling compounds also take the place of mortar on strong sub floors that are not level. A level floor is important for proper drainage. So, if you do not feel you can install a mortar bed but one is needed, contact a professional for assistance.