Mesh in plastering refers to a reinforcing material, typically a woven fabric or grid, embedded into wet plaster or render to strengthen the surface and prevent cracking. It acts as a skeleton within the plaster layer, distributing stress and increasing the overall durability of the finish.
Why is Plastering Mesh Used?
Plastering mesh is an essential component in modern construction and renovation, primarily used to enhance the structural integrity and longevity of plastered surfaces.
Key Benefits of Using Mesh
- Crack Prevention: The primary benefit is to minimize and prevent hairline cracks and larger structural cracks that can develop due to building movement, temperature fluctuations, or plaster shrinkage.
- Surface Reinforcement: It adds significant tensile strength to the plaster, making the surface more resistant to impact and abrasion.
- Adhesion Promotion: The mesh provides a key for subsequent plaster layers, improving adhesion, especially on diverse or challenging substrates.
- Enhanced Durability: By strengthening the plaster, it extends the lifespan of the rendered surface, reducing maintenance needs.
- Even Stress Distribution: It helps to spread stress uniformly across the plastered area, preventing stress concentrations that lead to cracking.
Where is Mesh Applied in Plastering?
Mesh is versatile and used in various applications, both internally and externally, to protect different parts of a structure.
Common Application Areas
- Building Facades: Plastering mesh is extensively used to protect the facades of buildings and structures, reinforcing the external render against weather elements and potential cracking.
- Around Openings: Plastic and fiberglass mesh are particularly effective at stress points where window and door frames connect to the wall. These junctions are prone to movement and cracking, and the mesh provides critical reinforcement.
- Wall-to-Floor/Ceiling Junctions: Similar to door and window frames, the areas where a wall meets the floor or ceiling are high-stress zones. Mesh is perfectly suited for these locations to prevent cracks from forming along these lines.
- Over Substrates with Varying Materials: When plastering over different materials (e.g., brick next to concrete block), mesh helps to bridge the potential stress points where these materials meet.
- Repair Work: It's frequently used to reinforce repaired areas, ensuring the new plaster bonds well and doesn't crack around the repair.
- External Wall Insulation Systems (EWI): Mesh is integral to EWI systems, where it's embedded within the base coat to provide reinforcement before the final top coat.
Types of Plastering Mesh
Different types of mesh are available, each suited for specific applications and plastering systems.
- Fiberglass Mesh:
- Description: Made from woven fiberglass threads, often alkali-resistant.
- Usage: Most common for external rendering, EWI systems, and general crack prevention. It's lightweight and easy to cut.
- Characteristics: Available in various densities (e.g., 145gsm, 160gsm), with higher densities offering greater strength.
- Plastic Mesh:
- Description: Made from extruded plastic polymers.
- Usage: Often used for internal plastering, smaller repair jobs, or specific applications where a lightweight, flexible option is needed.
- Characteristics: Generally less robust than fiberglass but still effective for minor reinforcement.
- Galvanized Metal Lath/Mesh:
- Description: Steel mesh coated with zinc to prevent rust.
- Usage: Historically used for heavier-duty applications, particularly in traditional lath and plaster systems, or when very thick render coats are applied.
- Characteristics: Provides strong mechanical key and robust reinforcement. Less common in modern light-gauge plastering but still has niche applications.
Mesh Characteristics Comparison
| Feature | Fiberglass Mesh | Plastic Mesh | Galvanized Metal Lath |
|---|---|---|---|
| Material | Woven fiberglass, alkali-resistant | Extruded plastic polymers | Galvanized steel |
| Primary Use | External rendering, EWI, general crack prev. | Internal plastering, light repair | Heavy-duty rendering, traditional lath/plaster |
| Strength | High tensile strength | Moderate | Very high |
| Weight | Lightweight | Very lightweight | Heavy |
| Flexibility | Good | Excellent | Limited |
| Cost | Moderate | Low | High |
| Corrosion | Excellent resistance (if alkali-resistant) | Excellent resistance | Good resistance (due to galvanization) |
Application of Plastering Mesh
The application process typically involves embedding the mesh into the first coat of wet plaster or render.
- Prepare the Surface: Ensure the substrate is clean, dry, and free from loose material.
- Apply Base Coat: Apply a consistent layer of the base plaster or render.
- Embed the Mesh: While the base coat is still wet, press the mesh firmly into the plaster. Overlap mesh strips by at least 10 cm to ensure continuous reinforcement. Pay close attention to corners and junctions, using corner beads or specific mesh strips for these areas.
- Cover with Second Coat: Immediately apply a second thin layer of the same base coat over the mesh, ensuring it is fully encapsulated and level.
- Allow to Dry: Let the reinforced base coat dry thoroughly before applying subsequent decorative or finishing coats.
Proper application ensures the mesh performs its function effectively, resulting in a durable and crack-resistant plastered surface. For detailed guidance, always refer to product specifications and industry best practices such as those outlined by The Plasterers Forum or similar reputable resources.
