Lath — Plaster and Stucco Backing System Guidebook

Lath is the narrow wood strip or metal mesh base used to support plaster, stucco, or certain tile backing systems.

What It Is

Traditional plaster walls were built by fastening thin wood lath strips across framing and then pressing wet plaster through the gaps so it hardened into keys behind the strips. Modern stucco and some masonry veneer systems use metal lath to provide a mechanical base for mortar or plaster coats.

Types

Common forms include wood lath in older interiors, expanded metal lath for stucco and masonry, and self-furred metal lath that stands off the substrate slightly for better embedment. Each type is chosen for a specific wall, ceiling, or exterior finish system.

Where It Is Used

Wood lath is found in older plaster walls and ceilings, especially in pre-drywall homes. Metal lath is used behind stucco, cultured stone, and some tile or mortar bed applications on walls, soffits, and exterior surfaces.

How to Identify One

If you open an old plaster wall and see rows of thin wood strips behind the plaster, that is wood lath. On exterior work, metal lath looks like galvanized mesh or slit-and-expanded sheet fastened over sheathing or a weather barrier.

Replacement

Damaged wood lath may be repaired locally during plaster patching, but large failures often lead homeowners to choose drywall over full lath-and-plaster restoration. Exterior metal lath is usually replaced whenever stucco or adhered veneer is removed in the affected area.