They do different jobs
The choice is usually presented as cheap versus expensive. It is not. Mesh and loose bar answer different questions, and picking the wrong one is not a saving.
- Mesh: A prefabricated sheet of light wires welded in a grid, typically 6 to 10 mm. It controls shrinkage cracking and distributes point loads across a slab. It is crack control, not structure.
- Loose bar: Individual bars, typically 10 mm and up, placed where the engineer says. It carries tension in a designed structural element — a beam, a suspended slab, a retaining wall.
A slab that only has to not crack wants mesh. A slab that has to span, cantilever or resist earth pressure wants bar, and the sizes and spacing come from a design, not a rule of thumb.
Where mesh is the right answer
- Ground-bearing domestic slabs: Garage floors, shed bases, patios. The ground carries the load; the mesh stops the slab cracking apart as it shrinks.
- Screeds and toppings: Thin layers over an existing base.
- Large flat areas: One sheet covers 4.8 × 2.4 m in a minute, where the same area in loose bar is an afternoon of tying.
The speed argument is real. On a big flat pour, mesh is dramatically faster to place, and labour is usually the larger cost.
Where only loose bar will do
- Anything designed: If a structural engineer has specified bar diameters and spacings, that is not a suggestion.
- Beams, lintels, columns: Concentrated tension in specific places, plus links and stirrups mesh cannot provide.
- Retaining walls: Earth pressure is a bending load and the steel has to be sized for it.
- Thickened edges and foundations: Where the load path concentrates.
- Congested or irregular shapes: Bar can be cut and bent to fit; a mesh sheet cannot.
The mistake that undoes either
Both fail the same way, and it is the commonest reinforcement error on small sites: the steel ends up at the bottom of the slab.
Mesh laid straight onto the sub-base and "lifted as you pour" does not get lifted. It stays where gravity puts it, in the zone of the slab that is in compression, where it contributes almost nothing — and where it will rust because it has no cover beneath it.
Use spacers. Set them out before the concrete arrives. This single detail matters more than the choice between mesh and bar.
Lapping mesh
Mesh sheets must overlap, and the overlap is measured in whole squares, not millimetres. Two full squares is the usual minimum, so a sheet with a 200 mm grid laps 400 mm. Wire the laps together so the sheets do not part underfoot during the pour.
That lap is a real quantity: on a slab needing several sheets, the lapped area can add 10 to 15 per cent to the sheet count, and it is easy to forget when working from bare floor area.
Cost, honestly
Per tonne, mesh and bar are broadly comparable. The real difference is labour: mesh goes down fast, bar takes time to place and tie. On a simple flat slab mesh wins on cost every time.
But the comparison only exists where both are structurally acceptable. Where a design calls for bar, mesh is not a cheaper alternative — it is the wrong material, and the saving disappears the first time the slab cracks through.