Jacuzzi Tub – Mortar or Construction Adhesive Base

So why is a mortar base preferred over using construction adhesive?

The answer is quite simple. Jacuzzis tubs are made out of fiberglass materials that are fairly rigid, but do flex to some degree. This flexing causes stresses on the Jacuzzi tub as well as creates squeaks. By resting the Jacuzzi tub in a bed of mortar any gaps, or voids, between the subfloor and the base of the Jacuzzi tub are filled. By filling the voids, the Jacuzzi tub is better supported and is less apt for flexing or squeaking.

On the other hand, simply applying a construction adhesive on the bottom surfaces of the support spacer blocks will prevent lateral movement of the tub, but does nothing in regards to offering additional support.

Installing Jacuzzi Tub into a Mortar Bed To install a Jacuzzi tub into a mortar bed first construct the 2×4 or 2×6 framing for setting the tub into. Make sure in the process of framing the Jacuzzi tub walls to specify an access location for the Jacuzzi tub’s electrical wiring and pump. Now, pour 2 inches of mortar, such as Quickrete Sand topping mix mortar, into the base of the Jacuzzi tub framed area. Make sure to leave voids in the mortar bed for the Jacuzzi tub pump and support legs. Read the Jacuzzi tub manufacturer’s directions to determine where the mortar voids should be located.

Next, immediately drape a layer of polyethylene plastic over the soft mortar bed.

Then immediately apply construction adhesive to the bottom of the Jacuzzi tub support spacer blocks.

Next, apply silicone adhesive around the top perimeter edge of the framed in area to create a water tight seal with the bottom edge flange of the Jacuzzi tub. Now place the Jacuzzi tub into the framed in area. Make sure the Jacuzzi tub sits properly on its support spacer blocks. Connect the electrical wiring and plumbing up to the Jacuzzi tub. You may need to have an electrical inspection completed by the building inspector at this point. Then install insulation around the Jacuzzi tub area to help retain heat.

Finally install greenboard or cement backerboard to the outside surface areas of the Jacuzzi tub area. Note that if you plan to tile around the Jacuzzi tub it is important to use a cement backerboard as it is meant for wet environments. Greenboard will not hold up to repeated moisture exposure.