North London Family Home Basement Waterproofing

North London Family Home Basement Waterproofing Project Overview

This North London family home basement waterproofing project formed part of the refurbishment of a substantial detached period house, together with a new basement extension incorporating a swimming pool. The scheme was a distinctive residential project in a sensitive North London setting, requiring a coordinated waterproofing strategy across both the main basement structure and associated external areas.

Renlon was asked to provide a waterproofing design for the basement to support a Grade 3 internal environment in accordance with BS 8102. The basement measured close to 1,000 sq ft and included a swimming pool. Because the front and rear sections of the basement extended partially beyond the footprint of the ground floor, the waterproofing design also needed to address external deck waterproofing alongside the main below-ground internal protection strategy.

The Challenge

This project required a waterproofing strategy capable of dealing with several different structural and environmental conditions within one coordinated design. The basement itself needed to support a Grade 3 environment under BS 8102, while also accommodating the specific demands associated with a swimming pool at lower-ground level.

The form of the extension introduced further complexity. Because parts of the basement projected beyond the ground floor footprint, the waterproofing approach had to protect both internal below-ground spaces and externally exposed deck areas. In parallel, the depth, scale and arrangement of the basement meant groundwater management had to be considered carefully from the outset.

To respond properly to the layout of the scheme, the overall waterproofing strategy also needed to incorporate dual pumping arrangements to suit different parts of the basement and the additional depth associated with the pool area.

Waterproofing Strategy

Renlon worked closely with Moreno Masey and Antvic to provide a coordinated waterproofing solution for the project. This comprised a primary Type B waterproof concrete structure by Antvic and a secondary Type C cavity membrane system installed internally. In addition, Renlon provided a Type A Polyurea waterproofing system to the rear external deck area and a Type A RenStrength system to the soffit internally at the front elevation plant room.

For the main basement, including the swimming pool area, the internal waterproofing build-up comprised Delta MS500 to the walls with Koster Anti Lime TG500, together with Delta MS20 to the floors, including perimeter channels and Koster Anti Lime TG500. This formed the core of the Type C cavity membrane approach within the wider waterproofing design.

Beyond the principal basement structure, Renlon also provided a hand-applied Type A Polyurea waterproofing system to the rear external deck area. This cold-liquid-applied membrane was designed to form a seamless, flexible and durable protective barrier suitable for the conditions at that part of the project. To the front elevation plant room soffit, Renlon provided its RenStrength Type A system to complete the coordinated waterproofing package.

Project Delivery

Because of the size and configuration of the basement, two groundwater dual pumping systems were required. At the front of the basement, a bespoke chamber measuring 800mm x 1200mm deep was installed. At the rear, a loose box system was formed using the concrete pit itself as the chamber, to a depth of 2m, in order to accommodate the additional depth associated with the swimming pool.

The waterproofing build-up to the front elevation plant room soffit comprised four main elements. These included an active water-stopping plugging compound to address persistent water ingress where required, a reactive waterproof slurry with self-healing properties, a pre-bagged render applied in two layers to encapsulate carbon fibre mesh, and the carbon fibre strengthening mesh itself to provide a stabilising layer within the build-up.

Outcome

This case study demonstrates how a coordinated Type A, Type B and Type C waterproofing strategy can be applied across a complex residential refurbishment and new basement extension for a family home in North London. Renlon delivered an integrated waterproofing solution designed to support the internal basement environment, swimming pool area, rear external deck and front elevation plant room soffit within one cohesive system.

The result was a waterproofing approach tailored to the structural layout, intended use and groundwater conditions of the project, while supporting the wider design requirements of a high-specification family home in North London.

You can also view more of our case studies across residential and commercial waterproofing projects.