Tanking a garage using Delta DualProof Waterproofing membrane

The Damptec team has been contracted to tank a garage at a new build property in Keyworth, Nottinghamshire. Our client aimed to convert the garage into a habitable space to use as an office. We proposed a combined waterproofing system:

• Type A: Barrier Protection – internal waterproofing

• Type C: Drained Protection – internal waterproofing

Type A and Type C are waterproofing barriers

Why Combined Waterproofing Systems?

When designing a structural waterproofing system for a new build below ground structure, it is essential to install two forms of waterproofing for combined protection. This approach is crucial as no single waterproofing system can be considered defect-free. The principle of combined protection is supported by BS 8102: 2022, which underscores its importance.

Major third-party warranty providers like NHBC, Premier Guarantees, and LABC also mandate combined protection as a fundamental condition of their warranties. They require the involvement of a CSSW-qualified waterproofing design specialist at the design stage.

Waterproofing Installation Process

WATERPROOFING TYPE “A”

First visit:

We installed the Delta DualProof pre-applied waterproofing membrane. The Delta DualProof membrane continues up the internal face of the external blockwork to roof height, installed prior to pouring the concrete slab and building the internal blockwork/infill. This fully bonded composite sheet not only waterproofs but also protects against gases and chemicals.

Second visit:

Ground floor

A Type A waterproofing ‘barrier’ system was applied to the internal floor in the form of a screed over the DualProof membrane as follows:

1. Application of primer to all surfaces in a spray coat application.

2. Installation of fillet seals at the base of the bund using repair mortar. The use of fillet seals helps to ensure a smooth transition between horizontal and vertical surfaces that will minimise the risk of leaving gaps or holes unsealed during the waterproofing works.

3. Application of two coats of Koster NB1 – Waterproof Tanking Slurry.  This is a cement-based, polymer modified, flexible, protective and waterproof membrane.  Coatings are applied to the internal surfaces.

WATERPROOFING TYPE “C”

Internal: Type C (Drained) Protection

• The secondary protection manages any water ingress due to installation defects, provided by a cavity drain membrane system.

Wall Cavity Drain Membranes

• Walls:  8mm membrane mechanically fixed to the internal face of the walls.

Drainage

• The effectiveness of the structure relies on discharging free water before pressure builds up behind the system. Gravity drainage has been installed via a waterproof bund running the full length of the building, including the rear and both sides (125mm wide). There is an option to recess the channel in the slab. The drainage channel needs maintenance; hence, jetting eyes/flushing points were installed at directional changes.