Versawall, Tasman & Modular Block Engineering

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What Are Modular Block Retaining Walls?

Modular block retaining walls use proprietary interlocking concrete block systems specifically designed for retaining applications. The two most common systems in Australia are Versawall (manufactured by Adbri Masonry) and Tasman (manufactured by Baines Masonry).

Versawall uses interlocking stacking lugs to build purely vertical walls. The split-face blocks (400 × 215 × 200mm) stack without setback, and cores are filled with no-fines concrete for structural mass. Maximum height is 800mm unreinforced or up to 1400mm with no-fines concrete and engineering.

Tasman uses a patented dry-stack interlocking system with a 10mm setback per course, creating a near-vertical wall. Blocks (390 × 225 × 200mm) can be built to 660mm unreinforced. For taller walls, FORTRAC geogrid reinforcement is locked into every second course to create a reinforced soil structure. Tasman offers a premium natural sandstone finish.

Both systems include purpose-made corner blocks, capping units, and half-blocks for clean finishing. Other similar systems (Keystone, Allan Block, Anchor) follow comparable engineering principles.

Engineering Design Considerations

System-specific design — Each manufacturer provides design charts and technical specifications. Our engineering works within these parameters while accounting for your specific site conditions — soil type, groundwater, surcharge loads, and slope geometry.

No-fines concrete (Versawall) — NFC fills the block cores and extends behind the wall, creating a monolithic mass. The aggregate-to-cement ratio (6:1 to 8:1) maintains drainage voids while adding structural weight. Bond between NFC and block units is critical — cores must be filled as courses are laid, not after.

Geogrid reinforcement (Tasman) — For walls over 660mm, FORTRAC geogrid is installed at every second course extending into compacted granular backfill. Grid length, type, and connection to the block face are specified per the manufacturer's design tables and AS 4678.

Base preparation — Compacted gravel levelling pad, typically 600mm wide × 150mm deep. First course embedded minimum 100mm below finished ground level. No concrete footing required for either system when built to manufacturer specifications.

Drainage — Both systems require free-draining gravel backfill (minimum 300mm zone) with slotted agricultural drain at the base. Versawall's NFC maintains drainage voids; Tasman relies on granular backfill drainage. Weep holes not typically required as drainage passes through/under the wall.

When Is Engineering Required?

Engineering is required for Versawall over 800mm and Tasman over 660mm, or any modular block wall on a property boundary. Most councils require engineering and a building permit for any retaining wall over 600mm. Engineering ensures the system is appropriate for your soil conditions and loading — manufacturer design charts assume standard conditions that may not match your site.

What You Receive

Our engineering package includes structural calculations to AS 4678, construction drawings showing block layout, NFC or geogrid specification, base preparation, drainage details, and an engineer's certificate for council. Drawings reference the specific product system being used.

Pricing

Modular block wall engineering starts from $600+GST for simple walls within manufacturer's unreinforced height limits. Walls requiring geogrid or NFC reinforcement design are typically $800–$1,200+GST.