Shrinkage mesh — also called crack-control mesh — is a cross-woven or welded steel wire mesh laid into a screed to limit cracking caused by shrinkage stress. It looks like reinforcing mesh but is noticeably lighter: it is not there to carry the floor, but to distribute the shrinkage.
What it does — and does not do
Shrinkage mesh does not prevent cracks. A cement screed shrinks as it dries, and that shrinkage is restrained by its bond to the substrate. What the mesh does is spread the stress: instead of one wide crack you get many fine ones, which under a tiled or poured finish are no longer a problem.
It adds no load-bearing capacity. A structural slab needs designed reinforcement, not shrinkage mesh.
How it is laid
- Mesh size — typically openings of roughly 5 to 15 cm. Finer distributes cracks better; coarser is cheaper and easier to handle.
- Material — preferably galvanised wire. In a thin screed the mesh sits close to the surface and can see moisture; rust expands and breaks the floor apart from within.
- Position — the mesh has to sit in the screed, not under it. Lay it on spacers or concrete blocks, at about mid-depth. Mesh left lying on the substrate does nothing.
- Laps — overlap the sheets by several squares and tie them where needed, so a continuous plane is formed.
When it really pays
- Under tiles and slabs. These crack along with the substrate. Mesh reduces the chance of one continuous crack carrying through into the tiling.
- With underfloor heating under tiles. Here thermal movement is added to shrinkage, and mesh is strongly advisable.
- On large uninterrupted areas. The bigger the area, the greater the accumulated shrinkage.
Always combine shrinkage mesh with the other measures: do not mix too wet, cure properly, use edge strips along the walls, and form contraction joints at the sensible places (doorways, changes in shape).
Measures to combine with shrinkage mesh
- Do not mix too wet: Keep the screed mix from getting too wet.
- Cure properly: Let the screed cure properly.
- Use edge strips: Place edge strips along the walls.
- Form contraction joints: Place them at sensible places, such as doorways and changes in shape.
Related terms
- Shrinkage
- Shrinkage crack
- Contraction joint
- Screed
- Underfloor heating
- Reinforcement
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