Glossary: Metal Lath
A structural steel mesh backing grid designed as a bonding support surface for Portland cement stucco plaster coatings.
Stucco Substrate Adhesion and Reinforcement
Portland cement plaster cannot bind directly to wood or foam building sheathing. Expanded metal lath provides a physical key that mechanical coatings hook onto. Under ASTM C1063 standards:
- Lath Weight Standards: Typically specified in pounds per square yard (e.g. 2.5 lb/yd² or 3.4 lb/yd²), with heavier lath suited for wide stud spans.
- Corrosion Protection: Metal lath is galvanized or coated to prevent structural moisture rust, which could lead to stucco failure and spalling.
- Application: Stucco is troweled onto the lath, pushing mortar through the mesh openings to form keys behind the steel grid.