Reinforcement Mesh Explained: SL72, SL82 and When to Use Them
Reinforcement mesh designations like SL72 and SL82 look like cryptic code, but they follow a logical system worth understanding if you want to genuinely follow your slab’s engineering.
What Mesh Designations Mean
Standard reinforcement mesh designations like SL72 and SL82 follow an Australian Standard naming system — the “SL” indicates a square mesh pattern with specific standard wire diameters and spacing, and the number relates to the mesh’s cross-sectional area and load capacity. Higher numbers generally indicate a heavier mesh with greater load capacity, though the specific engineering relationship is more nuanced than a simple linear scale.
Common Mesh Types
SL72 and SL82 are commonly used mesh types in residential slab construction, with SL82 generally providing greater reinforcement capacity than SL72 — the right choice for your specific slab depends on your engineer’s design calculations, not a default assumption. Other mesh types and designations exist for different applications and load requirements beyond standard residential use.
How Mesh Is Selected for a Project
Your engineer selects the appropriate mesh type based on the slab’s design loads, thickness, and the specific structural requirements calculated for your project — the same rigorous, project-specific process used for concrete strength and slab thickness. This isn’t a generic “standard mesh for all slabs” decision; it’s calculated for your specific circumstances.
Correct Placement and Cover
Mesh needs to be positioned at the correct height within the slab — supported by bar chairs to hold it up off the ground at the specified cover depth — for it to perform as designed. Mesh sitting on the ground, rather than properly elevated within the concrete, doesn’t provide the intended reinforcement benefit and is a genuine, avoidable construction quality issue worth being aware of.
Mesh vs Other Reinforcement Types
Mesh provides distributed reinforcement across a slab’s general area, while individual reinforcing bars handle more concentrated loads in specific elements like edge beams. See our reinforcement types guide for the full picture of how mesh, bar and fibre reinforcement work together in a complete slab design.
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Frequently Asked Questions
What's the difference between SL72 and SL82 mesh?
SL82 generally provides greater load capacity than SL72 — the right choice for your slab is calculated by your engineer based on your specific design requirements.
Why does mesh need to sit up off the ground?
Correct positioning within the concrete (cover), maintained using bar chairs, is essential for the mesh to provide its intended reinforcement — mesh sitting directly on the ground doesn’t perform correctly.
Can I check what mesh type is used in my slab?
Your engineer’s design documentation will specify the mesh type used — this is a reasonable thing to ask your contractor or engineer to confirm.
Is heavier mesh always better?
Not necessarily — the right mesh type is the one calculated for your specific slab’s loads and design, not simply the heaviest available option.
Does mesh alone provide all the reinforcement a slab needs?
Often mesh is combined with additional bar reinforcement in specific areas like edge beams, working together as a complete reinforcement system rather than mesh alone.
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