Plaster Reinforcement Meshes Technical Details
Understanding Plaster Reinforcement Mesh
Plaster reinforcement meshes are crucial components in modern construction, primarily used to fortify plaster, render, and screed systems. Their main function is to prevent crack formation due to thermal expansion, shrinkage, substrate movement, and impact. By embedding a mesh within the render layer, stresses are distributed across a wider area, effectively minimizing localized failures. These meshes are particularly vital in scenarios where dissimilar materials meet, at junctions between walls and ceilings, around openings, or over areas prone to stress concentrations.
Types of Reinforcement Meshes
Fiberglass Mesh Widely used for interior and exterior plastering, fiberglass mesh offers excellent tensile strength, lightweight properties, and ease of handling. For cement-based renders, it must be alkali-resistant (AR fiberglass) to prevent degradation from the high pH environment of the cement. Standard fiberglass mesh is typically used for gypsum plasters.
Polypropylene Mesh Lighter than fiberglass, polypropylene meshes are generally used in light-duty applications or as a base for spray plasters. They offer good chemical resistance but typically have lower tensile strength compared to fiberglass or steel meshes.
Galvanized Steel Mesh Provides superior strength and impact resistance. It is often employed in areas requiring maximum reinforcement, such as floors, industrial settings, or surfaces subjected to heavy impact. The galvanization protects the steel from corrosion.
Key Technical Specifications
Several technical parameters define the performance and application of reinforcement meshes:
Mesh Size Aperture This refers to the size of the individual openings in the mesh, typically ranging from 2x2 mm to 10x10 mm. Finer meshes (e.g., 4x4 mm) are suitable for thin-coat plasters and fine finishes, offering very close crack control. Coarser meshes (e.g., 10x10 mm) are often used in thicker render layers or floor screeds where greater structural reinforcement is needed.
Grammage (GSM) Expressed in grams per square meter (g/m²), grammage indicates the density and thickness of the mesh. A higher GSM generally correlates with greater material content, leading to increased tensile strength and durability. Common ranges for plaster reinforcement are 70 g/m² to 160 g/m², with heavier meshes used for high-stress areas or base coats for external thermal insulation composite systems (ETICS).
Tensile Strength Measured in N/50mm, tensile strength quantifies the force required to break a strip of the mesh. High tensile strength is crucial for effective crack prevention and structural stability, ensuring the mesh can withstand stretching forces within the render layer. Alkali-resistant fiberglass meshes often achieve high tensile strengths even at lower grammages due to their fiber composition and treatment.
Alkali Resistance Critical for meshes used in cement or lime-based renders, alkali resistance ensures the mesh fibers do not degrade over time due to the alkaline environment. For fiberglass meshes, this is achieved by incorporating Zirconia (ZrO2) into the glass fibers, forming AR fiberglass. Without adequate alkali resistance, the mesh would lose its reinforcing properties, leading to premature cracking and failure of the render.
Elongation at Break This property indicates the mesh's ability to stretch before breaking. A certain degree of elongation is desirable as it allows the mesh to accommodate minor movements and stresses within the plaster without snapping, thus maintaining its integrity.
Coating Many meshes are coated with a polymer dispersion to improve their adhesion to plaster, enhance alkali resistance, and prevent fraying during cutting and handling. The quality of this coating significantly impacts the mesh's performance and longevity.
Proper installation involves embedding the mesh within the middle third of the render thickness, ensuring it is fully encapsulated and free from wrinkles or bubbles, thereby maximizing its reinforcing effect.