What Is Lath in Construction in USA: A Detailed Professional Guide

Lath in construction across the United States is a foundational component essential for supporting plaster, stucco, and veneer finishes. Its use dates back centuries and continues to evolve with advancements in materials and building technology. As industry professionals, we recognize the importance of understanding what lath is in construction in the USA, how it’s used, the types available, and the regulatory standards that govern its application. This comprehensive guide provides clarity for contractors, architects, builders, and developers who work with lath as part of structural and aesthetic wall systems.

Definition of Lath in U.S. Construction

Lath is a framing or reinforcement material that provides a surface for plaster, stucco, or mortar to adhere to. Installed over structural components such as wood or metal framing, lath acts as a mechanical key that bonds the applied material to the surface. In American construction, lath is an essential part of cladding systems, interior wall finishes, and exterior façade solutions, particularly in residential and commercial buildings.

Types of Lath Used in Construction Projects Across the USA

Wood Lath

Wood lath was the original form used extensively before the 20th century. It consists of narrow, thin strips of wood nailed horizontally across wall studs.

• Standard Size: 1/4 to 3/8 inches thick, 1 inch wide, and 4 feet long
• Spacing: Around 3/8-inch gaps to allow plaster keying
• Use Case: Historical building restoration, specialty interiors

Expanded Metal Lath

The most widely used form today, expanded metal lath, is created by slitting and stretching sheet metal into a mesh pattern.

• Material: Galvanized steel, stainless steel
• Application: Supports stucco, stone veneer, and interior plaster systems
• Benefits: High tensile strength, superior adhesion, long service life

Welded Wire Lath

Welded wire lath is made from intersecting steel wires welded together into a grid.

• Configuration: Uniform square or rectangular mesh
• Strength: High structural load capacity
• Best For: Large-scale commercial projects, ceilings, and soffits

Self-Furring Lath

Designed to automatically create a gap between the lath and the substrate, self-furring lath allows plaster or stucco to bond correctly.

• Design: Dimpled or ribbed profile
• Benefit: Ensures consistent depth for mechanical bonding
• Application: Irregular or non-flat surfaces

Paper-Backed Lath

This variant combines metal lath with asphalt-impregnated building paper, providing both structure and weather resistance.

• Usage: Exterior stucco applications
• Moisture Control: Acts as a weather-resistant barrier
• Regulatory Standard: Meets ASTM C847 for metal lath

Fiberglass Lath

Fiberglass lath is a modern alternative offering excellent resistance to corrosion, moisture, and chemical exposure.

• Material: Alkali-resistant fiberglass mesh
• Lightweight: Easier to handle and install
• Ideal For: High-humidity areas, marine and coastal environments

Primary Applications of Lath in U.S. Building Systems

Stucco Wall Assemblies

Lath is a core component of traditional and modern stucco wall systems, used in both residential and commercial properties.

• Three-Coat System: Scratch coat, brown coat, and finish coat applied over lath and WRB
• One-Coat System: Base and brown coats combined in a single application layer
• Function: Provides tensile support and surface bonding for cementitious materials

Interior Plaster Support

Interior lath provides the foundational framework for plaster wall and ceiling systems in both restoration and new construction projects.

• Applications: Historic buildings, custom interiors, fire-rated assemblies
• Fire Resistance: Non-combustible metal lath contributes to UL-listed fire wall assemblies

Stone Veneer and Masonry Cladding

Stone and brick veneers rely on lath for adhesion support and structural stability.

• Bonding Base: Enables mortar to anchor stone securely to vertical surfaces
• Reinforcement: Prevents delamination, shifting, or cracking over time

Installation Standards and Technical Guidelines

ASTM and Building Code Compliance

Lath materials and installations in the USA must conform to specific industry standards:

• ASTM C847: Specification for metal lath
• ASTM C933: Welded wire lath for Portland cement-based plaster
• ASTM C1063: Installation of lathing and furring for Portland cement-based plaster
• ASTM C1780: Installation for adhered manufactured stone veneer

Installation Techniques

• Fastening: Use galvanized nails, staples, or screws depending on the substrate
• Overlap: 1-inch minimum side overlap, 2-inch end overlap
• Furring Requirements: Maintain appropriate spacing from sheathing using self-furring profiles or furring strips
• Support: Attach to studs, joists, or framing members every 6 inches on center

Weather Protection and Moisture Management

Water-Resistive Barriers (WRBs)

Lath must be installed over WRBs to prevent moisture intrusion and structural decay.

• Two-Ply WRBs: Required in most exterior stucco systems
• Flashing Requirements: Install at all penetrations and termination points
• Weep Screeds: Required at the base of exterior walls for drainage

Drainage Plane Integration

Some advanced lath systems include integrated drainage planes to allow trapped moisture to escape.

• Back-Ventilated Systems: Promote air circulation behind the cladding
• Compliance: Meets ICC-ES and local building codes

Advantages of Lath in U.S. Construction

• Structural Support: Reinforces wall finishes against movement and cracking
• Code Compatibility: Complies with seismic, fire, and energy regulations
• Versatility: Adapts to wood, steel, and masonry substrates
• Fire Resistance: Metal lath is non-combustible and contributes to fire-rated assemblies
• Enhanced Adhesion: Creates a stable matrix for cementitious materials to bond securely

Regional Construction Practices Involving Lath

Southwest USA

• Popular System: Three-coat stucco over metal lath
• Environmental Challenge: High UV and thermal expansion

Southeast USA

• Material Preference: Fiberglass lath to resist moisture and corrosion
• Application Need: Enhanced resistance to mold, hurricanes, and humidity

Northeast and Midwest

• Common Use: Wood and metal lath in restoration and retrofits
• Key Consideration: Freeze-thaw cycle durability and insulation integration

Industry Trends and Innovations in Lath Systems

Pre-Assembled Lath Panels

Prefabricated panels save installation time, reduce waste, and ensure consistent quality.

• Factory-Fabricated: Combine lath, WRB, and insulation layers
• Efficiency: Speeds up large-scale commercial installations

High-Performance Composite Lath

Engineered products that combine the best properties of metal and fiberglass are emerging in response to demand for long-term performance in extreme environments.

• Hybrid Materials: Improve tensile strength, flexibility, and environmental resistance

Digital Construction and Laser Layout

Digital site mapping allows precise placement of lath systems on complex surfaces.

• BIM Integration: Helps avoid clashes in multi-trade environments
• Robotic Installers: Emerging in large-scale commercial builds

Conclusion

Lath in construction in the USA remains a critical infrastructure element in modern building science. Its ability to adapt to different materials, comply with safety standards, and enhance finish durability makes it indispensable. Whether you’re constructing a multi-story commercial façade, restoring a historic home, or installing stone veneer on a custom residence, the correct selection and application of lath ensures structural integrity and long-lasting aesthetic performance. As construction codes evolve and materials advance, the role of lath continues to expand across architectural and engineering domains.

This article is crafted to provide an in-depth overview of what lath is in construction in the USA, covering its types, uses, standards, and emerging trends to serve professionals seeking reliable construction insights.