How to Build a Mud Pad for Ceramic Tile

Prepare the underlying surface. If you plan to install the mud bed on a concrete substrate, clean the concrete. On wood subfloors or situations in which the tile surface is subject to regular moisture exposure, staple or glue a waterproof membrane or moisture barrier to the underlying surface. Overlap any seams created by at least 2 inches.

Cut metal lath to fit the surface and staple it to the underlying wood subfloor, wall or counter material. If installing the mud pad atop concrete, do not attach the lath to the floor. Instead, wait until enough mortar is placed to make up about half of the thickness of the mortar bed, press the metal lath into the mortar and continue mortaring.

Prepare the mortar for the mud pad by developing a pre-mixed mortar according to the manufacturer's instructions. Use a liquid additive in place of some or all of the water to improve strength or other characteristics of the mud.

Pack mud into the metal lath or chicken wire using a trowel and spread a thin layer, only using as much as is needed to cover the metal.

Press the wooden screed strips into the mud, parallel to each other and close enough to each other and the walls so that the straightedge easily reaches at least two strips at a time. Use a level to make sure that all of the strips are even with each other, making minor adjustments as needed to ensure that the mud pad has an entirely even surface.

Pack mud to create the remainder of the pad, filling in the spaces between the wooden screed strips.

Run the straightedge over the mud, using the screed strips as a guide, and remove any excess mortar or fill in low spots. Smooth the surface with a wooden float.

Remove the wooden screed strips carefully once the mud begins to set.

Fill the spaces left by the wooden screed strips with mud and smooth them with the float. Let the mortar cure for an adequate period of time, which varies depending on the mud mixture and additive used, before applying the bond coat and ceramic tiles.