Basement waterproofing for a ground floor flat in London


Products Used: Delta Membranes MS20 Floor Membrane 20mm, Delta Membranes Dual V3 Sump and Pump Kit, Delta Membranes MS 500 Clear Membrane

Nestled on a bend of the River Thames cosily between Chelsea and Putney and with tree-lined Victorian and Edwardian streets in abundance, Fulham is arguably one of the more scenic areas in London.

Did you know?

Fulham received its original name “Fulanhamme” due to its proximity to the River Thames. Meaning firstly “the place” and secondly “of mud.”

The Timberwise London team were called upon to Stephendale Road, a short walk from Imperial Wharf station. As the owners of this typical turn-of-the-century terrace property began renovation works, it was evident that a below ground waterproofing system was not originally included. As a temporary measure, the owners had applied a bitumen waterproofing paint to the perimeter walls.

Liquid applied methods are considered a short-term measure for below ground structures, as they don’t comply with BS8102: 2009. The customer needed a Waterproofing Design Specialist to transform their damp and musty basement into a dry living space with a compliant, reliable and permanent waterproofing solution.

At the time of the survey, the property owners made Timberwise aware that the basement in question suffered from a considerable amount of water ingress within the light well abutting the front wall which was partially below ground. This had led to a very unattractive and unusable space with various spots of pooling. Due to the dark and damp conditions, this also made for the perfect breeding ground for elf cup fungus, which had started to grow up the perimeter walls.

Waterproofing Design Methodology

To give the customer the extra space they so craved, the design had to comply with British Standards Waterproofing Regulations (BS8102: 2009). BS8102: 2009 is a design document that guides methods of dealing with, and preventing, the entry of water from surrounding ground into a structure below ground level.

Type C System

Timberwise’s Waterproofing Design Specialist recommended a complete Type C system. A Type C system compromises of a cavity drain membrane and drainage system with accompanying sump and pump system. In principle, a cavity drain membrane system allows moisture to travel behind the membrane within a controlled drainage system.

Cavity Drain Membrane

The Type C waterproofing system was installed using a high-density extruded membrane moulded in a stud formation. The studs serve to hold the product away from the areas that have been treated, allowing an air gap behind the system in which water and water vapour can move unhindered in all directions thus achieving ‘damp pressure equalisation’.

Once Timberwise had completed the works, Timberwise Technicians then applied plasterboard the walls to give a smooth finish. The customer was then able to decorate straight away, with little disruption to their renovation works.

Perimeter Drainage Channel

The drainage system is fitted around the perimeter of the basement structural walls. It is an integral part of the system enabling any water ingress to be routed to the exit point whether it is natural drainage or a pumping system.

Jetting eyes are strategically placed along the route to enable maintenance by way of periodic power flushing. In this instance, Timberwise lay the drainage system into a perimeter rebate created into the existing floor slab.

This was a particularly interesting project from the initial consultation through to the project’s conclusion, Timberwise were able to bring the customer’s vision to life

Waterproofing Design Specialist

Sump Pump System

The sump and pump is the heart of the Type C system. The cavity wall membrane, floor membrane and drainage system will route any free-flowing water into the sump chamber. This water will need to be pumped away for disposal into designated drainage. The drainage to which the pumping system discharges must be regularly inspected and tested to ensure it is not blocked and obstructed, the water must be free-flowing; otherwise, backing-up and flooding could occur.

The sump chamber and pumping system are permanently formed and fixed within the floor slab in a location where it is always readily accessible for inspection and maintenance. The customer chose to have their builder undertake all of the preparation works, which included the removal of all current pipework fixtures and fittings and pre-installing the necessary electrics to connect automatically to the new sump pump system.

Type C cavity drainage systems must have blockage free drainage to prevent failure of the system. With the system installed and subsequently flood tested to ensure that water discharge correctly, Timberwise then worked alongside the customer’s builder to install the subsequent dryline system as to not a puncture any of the membranes. If the membrane is punctured, this then comprises the whole system.


All works carried out were accompanied by a 10-year guarantee for the products and workmanship. Maintenance of the system is critical to the performance of the waterproofing system. To ensure optimum performance, the customer also opted for a periodical, basement pump servicing with Timberwise.

Get in Touch With London’s Waterproofing Design Specialists

If you have any questions with any of the property care issues discussed then in touch experts. To book a basement waterproofing survey online simply call 0208 226 4168. You can alternatively you can request a survey online via filling in the form above.