2B2 Expamet Expanded Metal Mesh Lath

2B2 Expamet expanded metal mesh lath is a cold-formed, slit-and-stretched steel product engineered for structural reinforcement in plaster and render systems. Its diamond-pattern geometry creates mechanical interlock with cementitious materials, enhancing crack resistance and load distribution in both interior and exterior applications. Unlike woven wire mesh, the integral strand-and-node construction eliminates separation points, providing continuous reinforcement across large surface areas.

Material Composition and Manufacturing Process

The base material is typically low-carbon steel coil, selected for its ductility during the expanding process and sufficient tensile strength for reinforcement purposes. The coil undergoes precision slitting and simultaneous stretching through a series of dies, which transforms the flat sheet into an open mesh with uniform diamond openings. This process work-hardens the steel, increasing yield strength by approximately 20–30% compared to the original coil, while maintaining dimensional stability.

Standard thicknesses range from 0.4 mm to 0.8 mm, with strand widths between 2.5 mm and 4.0 mm, resulting in opening sizes commonly specified as 10 mm × 10 mm or 12 mm × 12 mm center-to-center. The expanded geometry achieves a minimum of 85% open area, allowing for effective embedment of plaster while minimizing material usage. Surface treatments include bare steel for interior use or hot-dip galvanizing (Z275 coating) for exterior or humid environments, meeting EN 10346 standards for corrosion protection.

Structural Performance Characteristics

The mechanical interlock formed between the expanded metal lath and plaster substrate relies on two primary mechanisms: transverse resistance from the strand edges and longitudinal anchorage from the nodes. Testing shows that pull-out resistance exceeds 1.2 kN per anchoring point under standard conditions, significantly higher than woven wire alternatives of equivalent weight. This performance reduces the risk of delamination in thick-coat applications (>15 mm) and improves impact resistance in high-traffic zones.

Flexural stiffness is directional due to the manufacturing process, with the longitudinal direction (parallel to strand length) exhibiting approximately 40% higher bending resistance than the transverse direction. Specifiers should align the lath with the primary stress axis in ceilings or walls where bending loads dominate. The product maintains dimensional stability under thermal cycling, with a coefficient of linear expansion matching that of steel (12 × 10⁻⁶/°C), minimizing differential movement with the substrate.

Applications in Construction Systems

In interior plastering, 2B2 Expamet lath is commonly used as a substrate for gypsum or cement-based renders on masonry, concrete, or timber studs. Its open structure allows keys to form behind the mesh, creating a positive mechanical bond that prevents hollow sounds and cracking at joints. For exterior rendering, the galvanized version provides a stable base for thick acrylic or mineral finishes on external wall insulation (EWI) systems, where long-term durability against moisture ingress is critical.

The lath is also specified in fire-rated assemblies, where its inorganic composition contributes to maintaining integrity during fire exposure. When embedded in vermiculite or perlite-enhanced plasters, it supports lightweight fire-resistant coatings on structural steel columns and beams. In renovation projects, it serves as a repair medium for cracked or spalled concrete, distributing new repair mortar evenly across deteriorated surfaces while conforming to irregular substrates.

Comparison Table: Key Specifications

Customization and Ordering Considerations

While standard configurations cover most general plastering needs, dimensional adjustments are possible to meet specific project requirements. Opening size can be modified by changing the die pattern during expansion, allowing for larger apertures (up to 20 mm × 20 mm) in applications requiring greater embedment depth or reduced material density. Strand thickness and width can be adjusted within the forming limits of the coil to increase tensile capacity or flexibility as needed.

Sheet dimensions are typically supplied in rolls or flat panels. Roll widths range from 600 mm to 1200 mm, with lengths up to 50 linear meters, minimizing seams in large-area applications. Flat sheets are available in standard building panel sizes (e.g., 1200 mm × 2400 mm) for easier handling in confined spaces. Edge conditions can be specified as trimmed or untrimmed, with trimmed edges reducing handling hazards during installation.

For projects requiring certified performance, material test certificates (MTCs) and declaration of performance (DoP) documents can be provided upon request, referencing EN 13658-2 for external rendering or EN 1323 for internal plastering. Lead times depend on coil availability and finishing requirements, typically ranging from 2–4 weeks for standard galvanized products. Samples are available for evaluation, including small cut sections or full-width samples to assess flexibility and mesh uniformity.

To discuss technical suitability, request a quotation, or obtain samples for your specific application, contact our technical team.