Should Fibreglass Mesh Plastering Be Embedded in The Base Coat Or The Top Coat?

The standard thin‑coat system follows a "two‑coat, mesh‑in‑between" process: first trowel on a base coat of plastering mortar, immediately press the mesh into it, then apply a second top coat to cover. This places the mesh in the lower‑middle portion of the mortar layer – about 2 mm from the insulation board and 3–4 mm from the finished surface. At this position, the mesh can absorb tensile stresses caused by substrate deformation and distribute them evenly across the entire mortar layer, preventing localised cracking. 

If the mesh is placed in or near the top coat, a thicker layer of mortar separates it from the insulation board. The thermal movement of the board is then not effectively transferred to the mesh, and stress concentrates within the mortar itself, leading to surface crazing. Moreover, a shallow mesh is easily damaged during sanding or finish application, losing its reinforcing function altogether. 

Both JGJ 144 and EOTA ETAG 004 specify that the mesh must be embedded in the plastering mortar on the side closest to the insulation. The reason is simple: the mesh's primary role is crack‑resistant reinforcement, so it must be near the source of stress while maintaining a minimum protective cover of at least 3 mm against alkaline attack.  

The first coat must be applied evenly and fully, ensuring the mesh is completely embedded without voids.

When pressing the mesh, use a trowel to embed it into the wet mortar, then immediately cover with the second coat. Total mortar thickness should be 5–7 mm.

Overlaps must be at least 100 mm, and corners should be reinforced with wrapped‑edge detailing.

The position of the mesh is the decisive factor in preventing cracks in thin‑coat plastering systems – always embed it in the base coat, never in the top coat. Proper technique combined with quality materials is the only way to ensure a durable, reliable insulation system. Our fibreglass mesh plastering is specifically engineered for plastering applications, with stable alkali resistance, high tensile strength, uniform grid dimensions, and standard specifications to suit your needs. We also provide technical guidance and on‑site support to help you place the mesh exactly where it belongs,every time.