Block Count by Wall Type

The block face area determines how many blocks you need per m² of wall:

• Standard besser block (390×190mm face): 12.5 blocks/m²
• Adbri MaxiWall: 9.5 blocks/m² (larger 600×190mm face)
• Allan Block / Versa-Lok: 10-12 blocks/m² depending on series
• Australian Hardwoods sandstone: 6-8 blocks/m² (large 500mm units)

The default 0.08 m² face area in the calculator matches a standard 390×190mm besser block. Override this for other product specs from the supplier datasheet.

When You Need an Engineer (AS 4678)

• Wall over 1.0m exposed height: always engineer-designed
• Surcharge load (driveway, building, pool) within wall-height distance: engineer required regardless
• Reactive soil (Class M, H, E): engineer recommended even for under-1m walls
• Slope steeper than 3:1 above wall, engineer required
• Multi-tier walls, engineer required (upper tier surcharges lower)

FAQs

How many besser blocks per m² for a retaining wall?

12.5 standard 390×190mm besser blocks per square metre of wall face. Add 5-10% wastage for cuts.

How much drainage aggregate behind a retaining wall?

Minimum 300mm wide drainage zone of 20mm blue metal, behind the entire wall face from base to within 200mm of finished surface. Wrap in geofabric to stop fines migrating in.

Do I need ag pipe behind the wall?

Yes for any wall over 600mm. Use slotted 100mm ag pipe wrapped in geofabric sock, laid at base on a 1:100 fall, discharging to a stormwater pit or rubble drain.

How do I calculate capping blocks?

Capping blocks are 400mm wide standard. Divide wall length (mm) by 400 and round up. They typically glue down with construction adhesive.