STUCCO NEWS.NET

An old wood lath and plaster application shows how plaster was supported. A gap was left in between the lath strips allowing mortar to be forced through to form keys.

Wood lath stucco base had the edges chamfered back for mortar keys when the lath was put on a substrate like sheathing or tarpaper.

A closer view of the bevel cuts.

Angle cuts allowed mortar to key, even when even when the lath was put on tight against a flat substrate.

An old house in the Brookland area of Washington, DC shows stucco base in action. The tarpaper was removed during major repairs from flood damge.

Floor joists where chiseled off at an angle for a metal lath and cement floor.

An illustration showing how splitting the joists at an angle allowing mortar to form full keys.

Without cutting off the joists at an angle, the flat areas form weak spots in the floor, leading to cracking and failure. It really gives me a pain to see someone put in a mud floor using flat lath and stiff mortar on plywood. The metal lath offers no reinforcement this way. You may as well just pour mortar on the plywood with no lath.

You may have seen our chipping method before. Chipping was used many years ago to plaster over old walls. In old buildings, I have found this plaster easy to knock off. Chipping alone isn't enough to bond mortar permanently to an old wall. A chemical bond is used along with chipping to ensure a permanent bond. The point is that holes are made allowing some mechanical key for the plaster..