Expanded mesh metal lath for plaster walls and ceilings © Daniel Friedman Expanded Metal Lath System: Diamond Mesh for Interior Plaster Ceilings & Walls & for Exterior Stucco

  • PLASTER LATH, METAL - CONTENTS: Plaster & plaster lath types, history, age determination. Properties of diamond mesh metal plaster lath. Properties of rib lath. Plaster System identification and history of use . Photo guide to expanded metal lath, diamond mesh lath, rib lath, wire mesh lath for plaster & stucco
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Installing plaster on expanded metal lath:

This article provides a photo guide to identifying and installing types of plaster support systems: metal lath, wire lath, etc. that are installed in buildings. We use building ceilings and walls as a photo and investigation guide to plaster and mortar lath systems.

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In this article series we describe and discuss the identification and history of older interior building surface materials such plaster, plaster board, split wood lath, sawn lath, and expanded metal lath, Beaverboard, and Drywall - materials that were used to form the (usually) non-structural surface of building interior ceilings and walls.

Expanded Mesh Metal Lath for Plaster Walls & Ceilings

Expanded metal lath has been widely used to support both interior plaster in buildings and exterior building wall stucco systems. This article explains plaster systems based on metal lath in building interiors. Also see STUCCO WALL METHODS & INSTALLATION for a discussion of exterior uses of stucco and metal lath.

Expanded mesh metal lath for plaster walls and ceilings © Daniel Friedman

Plaster of the same general formula as discussed in the two wood lath based installations above was later applied over expanded metal lath.

Our photo shows expanded mesh metal lath used as plaster lath support for ceilings and walls; this material was also used on building exterior walls to support a stucco finish.

Metal lath was on occasion used also to support poured concrete ceilings (shown here) - unlikely to provide adequate strength for a thick pour unless additional reinforcement was used.

Depending on building age we may find a mixture of multiple types of plaster support, wood lath, gypsum board lath, and metal lath.

Wall or ceiling or stucco crack patterns may follow the borders of metal lath segments, especially if the lath was not securely nailed.

Van Den Branden and Hartsellexplain that metal lath for plaster systems is divided into four groups with different properties for different applications:

  1. Expanded metal lath (diamond mesh plaster lath)
  2. Expanded rib lath (similar to diamond mesh but with stiffening ribs added)
  3. Wire lath (woven wire or welded wire - aka "chicken wire")
  4. Sheet lath (popular early in the history of use of metal lathing, with a resurgence of use when shot or gun-applied plaster or cement mortars became widespread, often in commercial projects)

Properties of Diamond Mesh Metal Lath

Properties of Metal Rib Lath

Properties of Wire Mesh Lath

Properties of Sheet Lath

Exterior Stucco Applications using Metal Lath

Van Den Branden and Hartsell continue to point out that metal lathing for exterior stucco is similar to interior installations, with these changes:

More photographs of plaster walls & ceilings built on metal lath:

Our ceiling cavity photograph of a plaster on metal lath system (below left) shows how plaster applied to metal lath has considerably more adhesion security than plaster applied over wood lath. At below right (a New York garage ceiling) the plaster coating was left quite thin; you can see rusting metal lath around the light fixture and at the upper right in our photograph.

Plaster lath board © Daniel Friedman

See Loose Plaster is Unsafe for an example of a collapse of an expanded wire lath ceiling that had been improperly installed.

Plaster lath board © Daniel Friedman

At below left we show a cut-cross-section of a steel-lath supported exterior wall on a Minneapolis, MN. home. Our photo at below right shows the marks left by metal lath on felt paper that had been used as a building sheathing wrap on the same home. These details were exposed during construction work for an addition.

Details about exterior stucco and metal lath are at STUCCO WALL METHODS & INSTALLATION.

Also see

Loose Plaster is Unsafe, Especially Loose, Falling Plaster Ceilings

Watch out: for loose plaster that can fall and injure building occupants. If ceiling plaster is bulged and moves when you apply gentle pressure to it, chances are that the plaster keys, the protruding plaster that oozed between the plaster lath strips to mechanically secure the plaster surface in place, have broken off.

Expanded Metal Lath Plaster Ceiling Catastrophic Collapse Case

As we discuss in detail at at PLASTER, LOOSE FALL HAZARDS, plaster ceilings in newer buildings are not immune from collapse either, as you'll see by the catastrophic ceiling collapse shown just below. This plaster ceiling was applied on expanded metal lath. The lath was wired to steel pipes or bars that in turn were hung from a smaller number of steel supports. The final steel supports were hung from wire ties connected to fasteners that had been "pin-shot fasteners" shot into the sides of concrete ceiling joists.

The combination of several factors led to this ceiling collapse:

Plaster lath board © Daniel Friedman

See DRYWALL, FIBERBOARD, PLASTER INTERIORS where we include photographs of non-plaster interior wall and ceiling coverings including drywall, beaverboard, and paneling

Plaster lath board © Daniel Friedman

For plaster type surfaces used on building exteriors, see STUCCO WALL METHODS & INSTALLATION.

Drywall & Plaster Articles


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