❌ The Result
The mesh is stuck at the back, resting on the EPS, and in front of it there is a thick, completely "bare" and unreinforced layer of adhesive.
Render Cracks: The Fatal Mistake with the Mesh
The thermal facade endures enormous daily stresses from sudden temperature changes (expansion and contraction). The material responsible for holding the render together and preventing "cracking" is the fibreglass mesh (the special glass-fibre net).
This mesh sits inside the adhesive (the so-called base coat), directly below the final coloured render. It works exactly like steel rebar inside concrete: it provides elasticity and tensile strength. But if placed incorrectly, your wall will crack - guaranteed.
1. The "Chessboard Syndrome" (The Fatal Mistake)
The most common mistake of rushed (or unskilled) crews is called "Dry Meshing".
How does the defect happen? The worker, to finish quickly, nails the dry mesh directly onto the bare polystyrene (with a few fixings or staples) to hold it in place. Then he takes his trowel and "smears" the adhesive over the top.
💥 The Destruction
When the first cold snap or heatwave arrives, this bare adhesive will expand. Because the mesh is buried behind it and cannot restrain it, the surface cracks. The cracks follow the board joints (polystyrene) underneath, creating a chilling pattern that looks like a chessboard on your wall! Rainwater will enter through these cracks and the system will rot.
2. The Correct Method: Perfect "Embedding"
The key word here is embedding. The mesh must not touch the polystyrene; it should "float" inside the adhesive mass, ideally in the outer 1/3 of the thickness!
How professionals do it (wet-on-wet method):
1️⃣ The First Coat
The worker first spreads a generous layer of adhesive onto the bare polystyrene using the notched side of his trowel (for uniform thickness throughout).
2️⃣ The Sinking
He takes the mesh and presses it gently onto the wet adhesive. The mesh begins to sink in.
3️⃣ The Smoothing
With the flat side of the trowel, he smooths the surface. The mesh has now been "swallowed" by the adhesive, yet remains close to the surface.
3. The Overlap Rule (10cm)
Furthermore, each mesh strip must overlap the next by at least 10 centimetres. If the mesh strips merely sit side by side, the wall will tear exactly at the joint!
How much does technique matter?
❌ Scenario A (Dry Meshing)
The contractor nails the mesh to the polystyrene and throws adhesive over it. He finishes early. The first winter, the temperature drops suddenly. The outer surface of the adhesive contracts, but the mesh cannot hold it (it is buried deeper). The wall "blows" and dozens of vertical and horizontal cracks appear. Rainwater enters inside.
✅ Scenario B (Correct Embedding)
The worker first spreads the adhesive, sinks the mesh, overlaps the joints by 10cm and smooths. The mesh now holds the entire adhesive mass together. Heatwaves and frosts come and go. The wall moves and breathes like one seamless, elastic skin, without a single crack forming for the next 30 years.
The Final Conclusion: When the crew starts the mesh phase, sit and watch them for 10 minutes. If you see them nailing the mesh "dry" onto the polystyrene, stop the work immediately. Correct embedding takes double the time, but it is the ultimate secret to a thermal facade that will never need patching.
Related Articles
Facade impact resistance (Double mesh reinforcement) The importance of water-repellent finishing renders How to check your contractor: Thermal facade checklist Application conditions: Temperature and humidity during construction
Application & Construction Details: Correct Installation Guide
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