Basement waterproofing for £1 million new build designed by award winning architects


Client: Arun Projects Ltd

Products Used: cavity membrane, perimeter drain channel, Koster NB1 waterproofing slurry

Set in the beautiful Hampshire village of Chilbolton in a quiet cul-de-sac location surrounded by countryside sits Pennard, a five bedroom detached new build home designed by Award Winning Architect, Adam Knibb. Pennard offers 3552 sq ft of open plan living space along with stunning views and an extensive lower ground level to the property.

Timberwise, as well as three other Waterproofing Designers, were called upon to tender for the waterproofing project. Following a site visit, the Timberwise waterproofing design team were able to identify the potential problems that external waterproofing systems as proposed by other designers, would have caused to the neighbouring structure.

External waterproofing would have resulted in the need for extensive excavation work to be carried out that would have been unavoidable for the basement to have been waterproofed. This would also have ultimately taken the final costs of the project over the budget in place. With this in mind, Timberwise Southampton designed the waterproofing system to comply with BS 8102 (The code of practice for protection of below ground structures against water from the ground) and Premier Guarantees strict guidelines and ultimately was awarded the project.

The Waterproofing Solution Methodology

Complying with BS.8102:2009. “Protection of below ground structures against water from the ground” and Premier Technical Manual Chapter 6 (Basements) guidelines, Timberwise proposed a combined system consisting of Type A and Type C waterproofing.

Type A (Barrier Protection) 

Type A protection is commonly known as ‘barrier protection’, this is where a material is put in place that offers a barrier to the passage of water with the aim of keeping the environment dry.

The water tightness of using a Type A system relies on the effectiveness of the preparation and the application. The customer was confident in the Timberwise Operatives, are fully trained in the specialist techniques required to carry out such waterproofing treatment.

Externally Koster NB1 waterproofing slurry was applied to the brick upstand from the beam and block up to 300mm to the perimeter as indicated on the plan. Koster NB1 was internally applied to the concrete block substrate to provide the first waterproofing barrier, and to conform to the Premier Warranty Chapter 6.1.

Being awarded the contract for Pennard is a great result for Timbewise. Working alongside award-winning architects Adam Knibb,  on such a prestigious and exciting project reinforces our reputation, as the “go-to waterproofing design specialists. We delivered results alongside other local contractors, whilst maintaining the highest levels of quality and service that they have come to expect

Jason Wakefield, Waterproofing Design Specialist CSSW

Type C (Internal Cavity Membrane)

Type C is usually the preferred method as part of a combined system for a new build, which made it the perfect solution for the basement at Pennard.  A complete Type C system is created using a cavity drain membrane, a perimeter drainage system and a suitable drainage point or sump pump.

The wall and floor system has been specifically designed for below ground installation and is a high density extruded membrane moulded in a stud formation. The studs serve to hold the membrane away from the areas being waterproofed allowing water to move freely behind the system and to drain away. In this way, water pressure does not build up behind the substrate or the membrane and the membrane also acts as a water vapour barrier. Such a system ensures that any internal wall or floor finishes remain dry.

Timberwise supplied and fixed 8mm cavity drain membrane to the walls using quick seal plugs and then laid 20mm cavity drain floor membrane. This was then sealed to the wall membrane and the perimeter drainage channel using the over seal corner tape.

Moreover, cavity drain membrane does not impose any load onto the structure or wall, it is also quicker to install than some other waterproofing systems, and easier to repair should there be a problem with the system at some point in the future. Overall, after facing and overcoming extreme weather and heavy snowfall and the challenges that come with excavating in close proximity with a neighbouring property, Timberwise were able to create a system that is flexible, maintainable and importantly carries a 10-year guarantee.

Commercial Waterproofing Design from the experts

Having designed and installed many different waterproofing systems across a broad spectrum of customers you can have confidence that Timberwise is your go-to team of waterproofing specialists to help with your project.

If you have any questions about how Timberwise can help you with your project, please feel free to chat directly with one of our Waterproofing Design Specialists who would be delighted to help you further. You can complete our contact us form or give us a call on 0800 288 8660.