How to Float Wall Mortar

Secure metal lath or similar wire reinforcing to the wall atop the waterproofing membrane. Each piece of wire reinforcement must overlap another by at least 2 inches and nails must be pounded into the studs and have their ends bent over to cover three wire strands.

Mix the mortar, adding any admixtures as desired or as suitable substitutes for clean water. For example, using a latex admixture rather than water can increase bond strength and flexibility.

Press mortar into the wire with a finish trowel or mortar hawk. Keep the mortar board below the work area for the sake of convenience and to catch any falling mortar. Fully fill and cover the wire so it is not visible. Work on and complete one wall at a time if the project must be divided into sections.

Score the mortar with a notched trowel or scratch coat tool. This will allow the next coat of mortar, the floated mortar layer, to adhere to this layer.

Prepare to embed the wooden float strips. The size of the wooden float strips should reflect the planned depth of the mortar bed. The mortar bed should be between one-half and three-fourths-inch. Float strips should be placed where they can be reached from the upper and lower ends of the wall if placed horizontally or where they can be reached from the corners if oriented vertically.

Place a strip or column of mortar where each float strip will be placed.

Embed a wooden float strip in the mortared strip. Use a level to ensure that the float is placed evenly.

Mix mortar and fill the walls. Use a finish trowel and mortar hawk and start by placing mortar in the area surrounding the float strips. Cut off excess mortar and fill in imperfections by running the featheredge over the float strip and wall. Continue placing mortar in the wall, working away from the float strip on either side. Mortar a few inches at a time before running the featheredge over the mortar to smooth it. Repeat this mortaring and smoothing until the entire wall is nearly covered.

Address corners or outer edges where the featheredge cannot easily reach by removing excess mortar with a finish trowel. Smooth these difficult-to-reach spots with a wood float, finish trowel or margin trowel.

Remove the wooden float strips carefully by cutting the mortar at the edges of the strips and gently pulling each out.

Fill the gaps left by the strips in with fresh mortar and use a wood float or finish trowel to remove excess mortar.

Rub the walls gently for a final smoothing with a wood float to ensure that the walls are totally flat.

Let the mortar bed cure for an adequate amount of time before applying a thinset mortar to set tile or stone.