RL818 (rectangular reinforcing mesh)
RL818 is a rectangular welded wire mesh under AS/NZS 4671: heavier longitudinal than transverse wires. Used in suspended slabs where one-way bending applies.
Ask Chalkline about this →RL818 is a rectangular welded wire reinforcing mesh specified under AS/NZS 4671:2019. The R prefix denotes rectangular: the longitudinal wires are heavier than the transverse wires, giving the sheet greater bending strength in one direction. The number 818 reads as 8 mm longitudinal bars at certain spacing, 8 mm transverse bars at wider spacing (full sheet dimensions per the AS/NZS 4671 mesh-designation table).
RL vs SL mesh
- RL (rectangular): heavier longitudinal, lighter transverse. Used where bending is dominantly one-directional, e.g. suspended slabs spanning one way, ribbed slabs, beam tops.
- SL (square): equal wire size and spacing in both directions. Used where load is roughly bi-directional, e.g. slab on ground, raft-slab top mesh.
A common residential pattern: SL92 in a slab on ground (top + bottom), RL818 or RL1018 in a suspended floor where one-way span is the load case.
Where it’s used
- Suspended concrete slabs spanning one way (intermediate floors over basements or garages).
- Ribbed concrete elements where ribs run in the dominant span direction.
The engineer’s slab schedule names the specific mesh code and lap arrangement. RL818 is not interchangeable with SL or a different RL number without engineer sign-off.
For a builder
- Match the engineer’s mesh code to the docket. RL818 and SL82 look similar on site; the difference is structural.
- Mind the lap direction. Heavy wires overlap heavy; lapping heavy-to-light halves the lap’s effective tensile capacity.
- Keep the docket with the slab record. Missing docket is a certifier defect at PCI.
Category: Materials / reinforcing.
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Last updated: 2026-05-29. Verified: 2026-05-29. Quarterly review for currency.