Basement Waterproofing

Structural waterproofing is essential for keeping buildings dry and liveable, especially with rising water levels, increased rainfall, and more frequent flooding. Water intrusion can cause severe damage, leading to thousands of pounds in repair costs.

To ensure the best protection at the lowest cost, it’s crucial to plan your building’s waterproofing as soon as possible. Below-ground structural waterproofing is a highly specialized task that requires skilled technicians and designers with the CSSW qualification (Certified Surveyor in Structural Waterproofing), along with full compliance with British standards 8102 and its updated version, 8102:2022. The VENTIL8ED team is fully equipped to provide expert, compliant waterproofing solutions.

Our design team specializes in structural waterproofing and will collaborate with you to select the most appropriate solution based on your needs. The choice of waterproofing system depends on the intended use of the space, what will be stored there, and the finishes it will have. These factors determine the level of waterproofing required. We offer three system types—A, B, and C—or a combined system, depending on the specific requirements of your project.

TYPE A

‘Protection against water ingress which is dependent on a separate barrier system applied to the structure.’

Otherwise known as Tanking, Type A waterproofing provides protection against groundwater ingress by applying a waterproof material to the external walls and floor slabs of a basement or underground structure forming a barrier between the structure and any groundwater present.

  • Can be applied either externally or internally.
  • Offers a double layer of protection.
  • Materials include Bonded Sheet Membranes, Liquid Applied Membranes, Geosynthetic Bentonite Clay Liners, Cementitious slurries and powders.

Close up, Type A barrier system complete using REMMERS MB2K

Complete Type A barrier system using REMMERS MB2K

Triton Admix TT Waterproofing issued at plant and introduced into the concrete mixture prior to arrival.

TYPE B

‘A structure that is waterproof by design; relies on the materials used and the design of the building.’

Type B protection places added importance on the design of the structure and the specification of materials as well as the quality of the workmanship involved in preparing and placing concrete. This is due to the fact that the pattern of any seepage encountered is often associated with poor joints, cracks or other discontinuities such as service penetrations.

  • Should be constructed of reinforced water-resistant concrete or structural steel.
  • Relies upon the design and materials incorporated into the external shell of the structure itself.

TYPE C

‘A water management system that controls and diverts water into a disposal point.’

Type C protection allows groundwater to penetrate through the external wall or floor as far as the cavity between the external shell and internal lining/finishes, collecting it via a Cavity Drain Membrane and then diverting it into controlled drainage and a designated safe point of disposal.

  • Protection against water ingress into usable spaces which is provided by the incorporation of an appropriate internal water management system.
  • Cavity Drain Membranes are studded on the external-facing surface, allowing any water that penetrates the structure to flow into the designed drainage channels
  • Water is carried to either a sump and pump chamber or away from the structure if passive drainage is possible.

Type C – Cavity Drainage Membrane system – Sump & Pump

Type C – Cavity Drainage Membrane system – During works

Waterproofing Grades explained: What will you use the basement for?

This is what Grades are in the updated BS8102:2022 standard:

GRADE 1a Seepage and damp areas from internal and external sources are tolerable, where this does not impact on the proposed use of below ground structure.

GRADE 1b No seepage. Damp areas from internal and external sources are tolerable.

GRADE 2 No seepage is acceptable. Damp areas as a result of internal air moisture/ condensation are tolerable; measures might be required to manage water vapour/condensation.

GRADE 3 No water ingress or damp areas is acceptable. Ventilation, dehumidification or air conditioning necessary; appropriate to the intended use.

The agreed grade should meet with client’s expectations for the intended use of the below ground space. Reducing the grade could increase the risk of not meeting the expectations of the client.

The grade of waterproofing protection should be agreed at the earliest stage. Reducing the grade increases the risk.

Seepage has been defined separately to damp, and specifically mentioned as either acceptable or unacceptable depending on the Grade of protection.

Waterproofing Thick Walls For Old Houses

If you are building a basement, you are required to carry out site investigations that involves inspection for ground gases.

Ventil8ed together with our partners provides combined solutions for both waterproofing and gas protection.

The provision of a waterproof membrane to the outside of the basement of substructure in accordance with BS8102/2022 (‘Type A’ form of construction) can also be a gas membrane and external tanking, and waterproofing can be combined where required.

Internal cavity drain membrane systems can be detailed as gas membranes/Radon barriers when married up with suitable extraction or positive pressure systems.