Estimated reading time: 4 minutes

Key Takeaways

• Vergelegen Plein in Somerset West needed level ground for parking and a new retail building on severely sloping land.
• LFC Construction installed 22,000 Terraforce L11 blocks to form retaining walls 6 m to 8 m high.
• Reinforced foundations, double-skin walls, geogrid and drainage let the walls carry buildings and parking right up to their edge.

Every metre of slope on a commercial site is a metre that cannot hold a car, a delivery truck or a building until the ground is retained and levelled. At Vergelegen Plein Shopping Centre in Somerset West, the fall across the site ruled out conventional construction altogether. The answer was a series of engineered concrete block retaining walls built by LFC Construction, a Terraforce Recommended Contractor.

By the end of this article, you will know:

• why a concrete block retaining wall suited a site with 6 m to 8 m height changes
• how the walls were founded, reinforced and drained to carry heavy loads
• what it took to build them on a site with difficult access

What Is a Concrete Block Retaining Wall?

A concrete block retaining wall is a wall built from interlocking precast concrete units that holds back soil where ground levels change. The blocks are stacked at a set angle and combined with drainage, compacted backfill and, on taller walls, geogrid reinforcement, so the structure resists both soil pressure and the loads placed above it.

On a commercial site, the wall also carries whatever sits on top. Terraforce L11 blocks were specified at Vergelegen Plein for their load-bearing capacity, and proved the most cost-effective option able to meet the site’s structural demands (Terraforce).

Creating Level Platforms for Parking and Retail Buildings

The land had to be reshaped before anything could be built. Fred Laker of iCOS Engineers designed the levels, and LFC built the walls across the site.

The walls serve four distinct purposes:

• Basement parking: walls build up and support the platform for the basement parking structure.
• Perimeter parking: embankment walls run out to the boundary fence, creating level parking across large grade changes.
• Detention pond platform: the most demanding section, with slopes of more than 6 m, forms the platform for a new retail building. It uses a double-skin wall filled with 4,200 m³ of G7 calcrete.
• Street embankments: walls along the road slopes stop soil eroding onto the surrounding roads.

On the detention pond platform, buildings, yard walls and parking bays stand right at the top of the wall, adding a surcharge load the structure must resist every day.

Engineered Foundations, Reinforcement and Drainage

A tall concrete block retaining wall is only as stable as the ground beneath it. Excavation went down to competent in-situ material with enough bearing capacity to stop the foundation sliding under load.

From there, the build followed the engineer’s drawings closely (Terraforce):

• Reinforced concrete foundations throughout, with Y12 starter bars set in every block up to the design height.
• Double-skin construction on the tallest sections, reinforced and filled with concrete.
• Geogrid tiebacks placed in the backfill every second or third course, depending on the surcharge on that section.
• Approved G7 backfill, a 400 mm drainage layer behind every wall, and an agricultural drain with weep holes at 2 m spacing.

For the client, the outcome is simple: the wall stays where it was built, carries parking and buildings, and sheds water after heavy rain.

Delivering a Complex Commercial Build in Phases

Steep sites test logistics as much as design. Foundations 6 m down in the detention pond area needed concrete pumps, and temporary roads and ramps gave trucks and TLBs access to raised platforms.

The project ran in phases from October 2022 to March 2023, with 22,000 Terraforce L11 blocks installed across the walls. All blocks came from Terraforce licensed manufacturers, so dimensions stayed consistent course after course.

This is the work LFC is set up for. As soil retention specialists, LFC carries projects through Design. Supply. Install., and every team works under experienced, full-time supervision on site. For developers, main contractors and engineers, that means one accountable specialist and walls built exactly to drawings.

Frequently Asked Questions

How high can a concrete block retaining wall be built?

Height depends on the engineered design, the soil and the loads above. At Vergelegen Plein, walls reached 6 m to 8 m with reinforced, double-skin sections and geogrid tiebacks, all built to an engineer’s drawings.

Can parking be built on top of a retaining wall?

Yes, provided the wall is designed for the extra surcharge load. At Vergelegen Plein, geogrid spacing was set section by section to suit the parking and buildings above.

Why does a retaining wall need a drainage layer?

Water trapped behind a wall adds pressure and softens the backfill. A drainage layer, a subsurface drain and weep holes let that water escape, so the wall carries only the soil and surcharge loads it was designed for.

Build on Difficult Ground with Confidence

A steep site does not have to limit a commercial development. Vergelegen Plein shows how an engineered concrete block retaining wall system can turn severe slopes into parking, access and building platforms that stand up to daily use.

If your project involves height changes, surcharge loads or a tight programme, contact LFC Construction for a site assessment, quote or tender enquiry. Explore LFC’s retaining wall services or speak to the team directly:

• Western Cape head office: Charl Johnsen, 079 073 7894, charl@lfcon.co.za
• Garden Route office: Adri De Klerk, 074 272 7699, adri@lfcon.co.za