What is ribbed expanded metal?
Ribbed expanded metal is thin expanded metal mesh, usually of galvanised sheet, with a rib depth of about 10 mm. Its main use is as permanent formwork to form a rough construction joint in concrete. The Dutch term is ribbenstrek or ribbenstrekmetaal.
Expanded metal is made by slitting a sheet and stretching it open, so that a mesh of diamond-shaped openings is created with no waste. The rolled-in ribs give the thin mesh its stiffness.
Use as construction joint formwork
When a concrete slab or wall is poured in sections, the construction joint has to be rough so that the next pour bonds properly and shear is transferred. Ribbed expanded metal is ideal:
- Cement paste passes through the mesh but the coarse aggregate does not, leaving a craggy, well-keyed surface
- Reinforcement can simply pass through it
- The mesh stays in the concrete: there is nothing to strike
Support: allow a bearer spacing of around 150 mm, depending on the concrete pressure. The higher the pour and the more fluid the mix, the closer the support needs to be.
Other uses
- Plaster lath — a version backed with absorbent paper holds the render back and is used to plaster over substrates that offer no key of their own
- Fire-protection systems — as a carrier for sprayed or trowelled fire-protection mortars
- Facade cladding — as an open, gauze-like facade veil, for instance in copper or aluminium, hung clear of the wall
Safety
The cut edges of expanded metal are razor sharp. Always work with cut-resistant gloves, long sleeves and eye protection, and clear offcuts away immediately.
Related terms
- Formwork
- Reinforcement
- Mortar
- Facade
- Compressive strength
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.