Do I Need Cement Under My Shower Base?
A shower base is a one-piece unit installed on the shower floor. It has a drain and a lip edge to funnel shower water towards the drain line. For this reason, the base requires a flat floor for proper installation. In some cases, a layer or cement is necessary for the installation of a shower base.
Nonetheless, it depends on what type of floor your showering area has.
Typical Wood Floors
If you're installing a shower base on a wood floor covered with plywood or a similar type of particle board, no cement is necessary under the shower base, as long as the flooring is flat and strong. Typical plywood and particle board is strong enough to support shower bases. If the floor is not level, however, a cement bed will help provide a better installation. If your shower base manufacturer recommends a cement bed, you should install one to avoid any complications down the road. Some shower bases require a cement bed to provide proper support of the shower base floor and to facilitate drainage.
Second Story Floors
Cement beds add extra weight to your flooring, so when installing a shower base on a third or second floor consider this additional weight. If the subfloor is weak or rotted, replace the subfloor first before installing the cement bed. A mortar bed will not add so much weight that it jeopardises the stability of a well-built and well-maintained floor. However, it is a danger on rotted floors. It is always prudent to pay attention to this fact whenever you install cement. If the floor is solid, level and flat, a cement bed is not required although recommended by many shower base manufacturers. It is OK to skip this step if your manufacturer does not recommend it. Bare in mind, the cement bed may prevent voids from forming between the floor and pan as time goes on.
Concrete Floors, Ground Floor Units and Basements
If you are installing a shower base on a bare, flat and level concrete floor, no additional cement layer is necessary. However, if the concrete is chipped, cracked or uneven, a layer of levelling compound is necessary to make a flat surface for installation. This layer provides the right type of surface for the installation. While the concrete is hard enough to support the shower base, an uneven floor prevents the base from draining properly. It also prevents pockets and gaps from forming between the floor and the shower base.
When Installing Cement Beds
The most effective way to install a cement bed on any type of floor is to press a dam into the drain hole. A piece of pipe or similar cylindrical object works well as a dam. You should mix the mortar in a bucket with a cement mixing bit or by hand with a trowel. You'll want to keep it soft and apply it to the floor with the trowel. You can then spread it evenly and check the spread for levelness. Use a large float tool to make the surface perfectly flat, then set the shower base into the mortar. The cement supports the base with only a few gaps or pockets between the floor and the shower base.