West bradley below Ground Waterproofing

Case Study: Below‑Ground Waterproofing – Specialist Koster System Installation

Client: Stonewood Builders Ltd
Location: West Bradley, Somerset
System Installed: Koster TG500 & Koster NB1
Specification Reference: NBS J40 – Cementitious Waterproofing

Project Overview

Cannon Clarke were appointed by Stonewood Builders Ltd to deliver the waterproofing package for a newly constructed below‑ground structure forming part of a high‑end residential development in West Bradley, Somerset. The project required a robust, fully bonded waterproofing system capable of protecting the structure from long‑term moisture ingress and meeting the performance expectations of a Type A waterproofing solution.

Why Waterproofing Matters in New Build Basements

Below‑ground structures are naturally exposed to groundwater pressure, moisture vapour, and seasonal fluctuations in soil conditions. Without a properly installed waterproofing system, new basements can suffer from:

• Damp patches and moisture staining
• Water ingress through pores, joints, or cracks
• Salt migration and efflorescence
• Long‑term structural deterioration
• Compromised internal finishes

By installing a J40‑compliant waterproofing system at the construction stage, Stonewood Builders Ltd ensured the new structure would remain dry, stable, and ready for future fit‑out.

Our waterproofing Strategy

Cannon Clarke specified a two‑part Koster system designed to stabilise the concrete substrate and create a durable, crystalline waterproof barrier.

Works Carried Out

Koster TG500 – Deep Penetrating Primer

Koster TG500 was applied first to consolidate the new concrete and prepare it for the NB1 coating. This product:

• Penetrates deeply into the substrate
• Reduces salt migration
• Strengthens the surface
• Improves adhesion of cementitious coatings
• Supports J40 requirements for substrate preparation

Koster NB1 – Crystalline Waterproofing Slurry

Koster NB1 was then applied as the primary waterproofing layer. This cementitious slurry:

• Forms insoluble crystalline structures within the concrete
• Resists both positive and negative hydrostatic pressure
• Creates a breathable, mineral‑compatible waterproof barrier
• Provides long‑term durability for below‑ground structures
• Meets the performance expectations of NBS J40

Together, TG500 and NB1 create a fully bonded, high‑performance waterproofing system ideal for new build basements.

Our Installation Process

1. Substrate Preparation

We prepared the new concrete surfaces by:

• Mechanically cleaning and removing laitance
• Treating early shrinkage cracks and construction joints
• Ensuring a clean, sound substrate ready for coating
• Following J40 guidance for substrate condition and preparation

2. Application of Koster TG500

TG500 was applied uniformly to all surfaces, allowing full penetration to stabilise the concrete and create a consistent base for the NB1 slurry.

3. Application of Koster NB1

NB1 was mixed and applied in multiple coats to achieve the required thickness and coverage. Particular attention was given to:

• Corners and junctions
• Service penetrations
• Wall‑to‑slab transitions
• Areas of increased moisture exposure

A final inspection ensured continuity and integrity of the waterproofing layer.

Project Outcome

The completed works delivered a high‑performance, J40‑compliant waterproofing system that provides long‑term protection for the new below‑ground structure. The TG500/NB1 combination ensures:

• Excellent adhesion to new concrete
• Resistance to water pressure from both sides
• A breathable, mineral‑based finish
• Compatibility with future internal finishes
• Confidence for the client, warranty providers, and future occupants

Stonewood Builders Ltd were able to continue construction knowing the structure had been protected using a manufacturer‑approved system installed by trained specialists.

Why Clients Choose Cannon Clarke

Cannon Clarke specialise in delivering technically robust waterproofing solutions for new build and existing structures. Our installations follow:

• Manufacturer guidance
• Industry best practice
• Relevant NBS specification sections
• Proven, long‑term waterproofing methods

We combine technical expertise with clear communication, ensuring every client understands the system being installed and the protection it provides.

Looking for a Waterproofing Specialist?

If you’re planning a new build basement, retaining wall, or below‑ground structure, Cannon Clarke can provide a tailored waterproofing solution using industry‑leading systems such as Koster, Delta, and other approved manufacturers.