Stroud New Build Retaining Wall Waterproofing – Case Study

The Client

A new build residential property in Stroud, Gloucestershire. Part of the structure was set into the hillside, creating below-ground retaining conditions.

The Brief

Provide a dependable external waterproofing system for approximately 80m² of retaining walls. The solution needed to prevent water ingress, manage hydrostatic pressure, and remain straightforward to install within the build programme. A five-day installation window was allocated.

The Challenge

Building into a slope exposed the retaining walls to persistent ground moisture and periods of increased water pressure. The system needed to create a robust waterproof barrier while also relieving pressure at the wall face. The specification also had to stand up to backfilling without the need for additional protection boards, relying on careful placement and compaction of suitable backfill.

The Solution

A combined barrier-and-drainage approach was selected. The retaining walls were coated with PermaSEAL PRO MP 2C to create a continuous, flexible waterproof layer with strong adhesion to the substrate. This provided primary resistance to damp and hydrostatic pressure.

Over the cured coating, PermaSEAL 8 Geodrain was installed externally as a tough cavity drainage membrane. Geodrain protects the coating during backfilling and establishes a ventilated drainage gap between the geotextile filter fabric and the 8mm studs, so any groundwater is depressurised and rapidly channelled down to the base and away via the below slab level drainage. No additional protection boards were required due to controlled, careful backfilling.

Products Used

• PermaSEAL PRO MP 2C – A flexible, two-component waterproof coating providing a durable, watertight barrier and strong bond to the wall, resisting moisture and hydrostatic pressure.
• PermaSEAL 8 Geodrain (40m²) – A high-performing external cavity drainage membrane that protects the coating during backfill and efficiently channels groundwater away from the structure.

Results

The system delivered a robust, maintainable external waterproofing solution across the 80m² retaining wall area within the allocated five days. The MP 2C barrier works in tandem with the Geodrain membrane to mitigate hydrostatic pressure and prevent water ingress, safeguarding the structure for the long term while simplifying future maintenance.

Why This Matters

For homes set into a hillside, reliable external waterproofing is essential to control moisture, prevent mould, and protect structural integrity. This Stroud project shows how pairing a proven waterproof coating with an efficient drainage membrane provides long-lasting performance without the need for additional protection boards when careful backfilling is used.

Permagard – Providing Solutions. Inspiring Confidence.

Permagard supplies trade-trusted damp proofing and waterproofing systems backed by free technical advice, specification support, and reliable 1–3 day delivery. With 35+ years of experience, we help you get it right first time. For expert guidance, call 0117 982 3282 or email [email protected].