Lath Lath in Construction in USA: An In-Depth Industry Overview

In the construction industry in the United States, lath serves as an essential support structure used in plastering, stucco installation, and masonry applications. This versatile building material is critical to forming durable, code-compliant wall systems in both residential and commercial projects. In this article, we explore every aspect of lath lath in construction in USA, covering its types, functions, applications, installation standards, and regional preferences. Our focus is delivering precise, technical insights for professionals involved in building, designing, or inspecting wall systems that incorporate lath.

What Is Lath in Construction?

Lath is a base framework made of wood, metal, or synthetic mesh that supports the application of wet finishing materials such as stucco, plaster, or mortar. Installed over framing studs or sheathing, lath allows finishing materials to “key” or bond securely, ensuring structural integrity, surface durability, and long-term adhesion.

Types of Lath Commonly Used in U.S. Construction

Wood Lath

Wood lath is a traditional solution, primarily used in historic or restoration projects.

• Material: Sawn hardwood or softwood strips
• Dimensions: Typically 1/4″ to 3/8″ thick, 1″ wide, and 4′ long
• Installation: Nailed with consistent spacing to form gaps for plaster keying
• Use Cases: Historic renovations, interior plaster walls, vintage ceiling finishes

Expanded Metal Lath

Expanded metal lath is the industry standard for modern stucco and veneer applications.

• Material: Galvanized steel or stainless steel
• Design: Diamond-shaped mesh created by slitting and stretching
• Properties: Rust-resistant, strong, flexible, and durable
• Applications: Three-coat stucco, veneer stone, fire-rated assemblies

Welded Wire Lath

This type features welded intersections for added rigidity.

• Configuration: Square or rectangular steel wire grids
• Strength: Higher structural support than expanded metal
• Best For: Commercial façades, ceilings, structural backup for stone cladding

Paper-Backed Lath

Combining lath and moisture protection, paper-backed lath integrates weather-resistant barriers into the mesh.

• Composition: Expanded metal with asphalt-impregnated Kraft paper
• Purpose: Combines drainage, adhesion, and weatherproofing in one product
• Regulation: Meets ASTM C847, ICC-ES ESR-2561 for exterior wall systems

Fiberglass Lath

A non-corrosive, lightweight alternative, fiberglass lath is suitable for specific environments.

• Material: Alkali-resistant glass mesh
• Weight: Lightweight for faster installation
• Suitability: Ideal for coastal, humid, or chemically sensitive environments

Core Applications of Lath in American Construction

Three-Coat Stucco Systems

A standard in the U.S., this stucco method relies on lath for structural support.

• Layer 1 (Scratch Coat): First application adheres to the lath and is scored for bonding
• Layer 2 (Brown Coat): Levels the wall and provides additional thickness
• Layer 3 (Finish Coat): Adds color, texture, and final protection
• Base Support: Expanded metal or paper-backed lath ensures proper bonding

Interior Plaster Walls and Ceilings

Lath is the foundational element behind traditional plaster systems.

• Support: Ensures the plaster mix adheres to vertical and horizontal surfaces
• Fire Resistance: Contributes to rated assemblies with proper installation
• Detail Work: Enables curvature and intricate finish in domes, coves, and trims

Adhered Stone Veneer Installations

Lath provides a mechanical bond for mortar used in stone and brick veneer systems.

• Load Transfer: Evenly distributes veneer weight to substrate
• Surface Texture: Enhances grip of mortar to surface
• Codes: Must meet requirements of ASTM C1780 and local jurisdiction codes

Installation Requirements and Best Practices

Industry Standards

Lath systems must conform to multiple regulatory guidelines:

• ASTM C847: Metal lath specifications
• ASTM C933: Welded wire lath
• ASTM C1063: Application of lathing and furring
• ICC-ES Reports: Product evaluation for code compliance

Fastening Guidelines

• Fasteners: Corrosion-resistant staples, nails, or screws
• Substrate Compatibility: Attach to wood, metal framing, or masonry walls
• Spacing: Fasteners every 6 inches along framing
• Edge Overlap: Minimum 1″ side, 2″ end overlaps for all types of metal lath

Water and Vapor Management

• WRB Requirements: Two layers of weather-resistant barrier behind exterior lath
• Flashing: Essential at openings and transitions
• Weep Screeds: Required at base of framed walls to drain moisture

Lath and Building Codes in the USA

Seismic Zones

In areas like California and Nevada, lath must withstand seismic activity:

• Installation: Enhanced fastening and high-tensile materials
• Mesh Strength: Reinforced lath with additional ribs or welded wire

Fire Ratings

Lath contributes to 1-hour and 2-hour fire-rated assemblies:

• Non-combustible: Expanded metal and welded wire lath qualify for use in rated walls
• Underwriters Laboratories (UL): Use listed assemblies that specify lath configuration

Wind Loads

In coastal and hurricane-prone regions:

• Fastening Patterns: Must meet higher wind-load resistance
• Substrate Reinforcement: Enhanced sheathing and corner lath details required

Regional Use of Lath Across the United States

Southwest USA (CA, AZ, NM)

• Common Material: Expanded metal and paper-backed lath
• Building Style: Spanish Colonial, Mission-style, heavy stucco use
• Climate Adaptation: High UV and dry conditions require thermal-stable materials

Southeastern USA (FL, GA, SC)

• Material Focus: Fiberglass and corrosion-resistant lath
• Environmental Challenge: High humidity, salt exposure, hurricane resistance

Northern and Midwest States

• Use Case: Wood lath in historical renovations; metal lath in modern upgrades
• Seasonal Considerations: Freeze-thaw resistance and thermal expansion key

Modern Trends and Advancements in Lath Technology

Pre-Attached Drainage Mats

Advanced lath systems now feature integrated drainage planes for moisture management.

• Drainage Composite Lath: Combines lath, WRB, and a cavity system
• Functionality: Promotes airflow and water drainage behind veneer or stucco

Hybrid Composite Mesh Systems

Innovative products combine the benefits of metal and synthetic materials.

• Strength and Flexibility: Delivers superior crack resistance and durability
• Ease of Use: Lightweight, cuts easily, and reduces installer fatigue

BIM and Digital Construction Integration

Lath layouts are now incorporated into Building Information Modeling (BIM) workflows.

• Benefits: Accurate estimating, conflict detection, and schedule integration
• Field Coordination: Enhanced communication between trades for envelope systems

Why Lath Remains Indispensable in U.S. Construction

• Adhesion Platform: Essential for cementitious materials to grip surfaces
• Structural Support: Distributes loads across cladding systems
• Moisture Barrier Compatibility: Integrates with WRBs and flashing systems
• Fire and Seismic Performance: Supports rated assemblies and seismic detailing
• Longevity: Extends the life of stucco, plaster, and veneer finishes

Conclusion

Lath lath in construction in USA is far more than a hidden element behind stucco or plaster—it is a critical structural and performance component of the building envelope. From residential homes to commercial towers, from dry deserts to humid coastlines, lath adapts to a wide range of architectural requirements and climate challenges. Understanding the types, proper installation, and code requirements ensures that lath will continue to perform its role effectively, providing stability, safety, and superior finishes for generations of American construction projects.

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.