How to Mortar a Shower Bed on a Slope

Cover the subfloor with building, tar or felt paper. The construction paper utilized should ideally be 15-pound.

Glue the lowest piece of the three-piece shower drain into the drain opening using PVC cement. Shower drains, unlike standard fixture drains, consist of three pieces that are assembled throughout shower pan construction to create a watertight seal.

Measure from the center of the drain straight to the center of the wall farthest away from the drain and mark this spot.

Calculate the amount of rise that will be required. The mortar bed should rise at least 1/4-inch for each foot of distance. For example, if the center of the drain is 2 1/2-feet from the center of the farthest wall, the mortar should rise at least 5/8-inch between the drain and the wall.

Measure the distance of the calculated rise up from the original point on the wall and mark this new spot.

Draw a line at this level around the perimeter of the shower using a level to ensure that the line is even.

Staple metal lath to the floor on top of the construction paper, cutting out a space in the metal for the drain.

Stuff a rag into the drain opening to keep mortar from accidentally falling into the drain.

Prepare the mortar for this level, the pre-pan. Mix a thinset mortar so it has a fairly dry consistency and use a latex additive to improve strength.

Trowel the mortar onto the floor, packing it into the metal lath and spreading it from the flange of the drain to the wall, building it up to the line on the wall to account for the slope.

Place the level or an appropriately sized board with one end on the drain and the other end at the line on the wall once the mortar has been troweled and roughly shaped.

Make adjustments to fill in any low spots or remove mortar from high spots using the straight edge of the level or board as a guide.

Float the surface of the mortar by running a wooden float over the mortar and again check with a level or board to ensure the surface is even, smooth and sloped correctly. Let the mortar cure for at least a day before continuing construction of the pan.

Build the remainder of the shower pan. Glue a waterproof membrane to the pan, cutting small holes in the membrane to attach and tighten the drain to create a watertight seal. Attach the final drain piece, the strainer, and adjust it to reflect the depth of the planned mortar bed, typically about 1 1/2 inches. Measure and mark this height around the perimeter of the shower.

Apply mortar to about half the height marked in Step 14. Lay a piece of metal lath and mortar the remainder of the bed. This mortar layer should be of uniform thickness to maintain the slope established by the mortar in the pre-pan.

Float the surface of the mortar and check with a level to make sure the mortar bed reflects the planned slope. Let the mortar cure and place tile or otherwise finish the bed.