From Volcanic Soil to Solid Solutions: Redi-Rock Gravity Wall Delivers Stability and Style in New Zealand

The Challenge: Finding Stability in Volcanic Soil

At the hillside entry to Ashbury Heights Retirement Village in Whangarei, Northland, New Zealand, retaining walls were needed to manage grade changes. However, the site’s volcanic soil and large subsurface rocks posed a significant geotechnical challenge.

While traditional timber pole walls were initially considered, the lack of deep, stable soil made them impractical and unreliable. These conditions led the design team to seek a more adaptable, engineered solution, specifically a system that could perform in New Zealand’s unique geology and visually emulate a natural stone wall.

Why Redi-Rock? Engineered Strength Meets Natural Beauty

Project designer Babbage Consultants selected a Redi-Rock gravity retaining wall system, eliminating the need for extensive excavation or costly foundation modifications. Relying on the weight of massive Redi-Rock concrete blocks and their engineered interlocking design, a gravity wall solution provided the stability needed to maintain grade even in rocky and unpredictable subsurface material.

Beyond performance, Redi-Rock’s Ledgestone texture played a key role in the selection process. The natural, quarried-stone aesthetic allowed the wall to blend into the surrounding landscape - an important consideration for the project stakeholders. By combining structural performance with visual interest, Ashbury Heights’ designers delivered a retaining wall solution that provided:

• A retaining wall design leveraging the full strength of the Redi-Rock block library with 60 in (1520 mm), 41 in (1030 mm), 28 in (710 mm), and free-standing corner blocks with a 5-degree batter.
• Minimal excavation and shallow foundation capability in rocky, volcanic soil
• Proven engineering backed by technical support and design tools
• Aesthetic appeal with the Ledgestone texture
• Long-term durability and design flexibility with a gravity wall system
• Locally sourced blocks from New Zealand producer Duracrete

To this point, 3,611.6 sq ft (335.5 sq m) of Redi-Rock walls have been installed at Ashbury Heights. Additional walls are planned for future construction for this stunning New Zealand project.