Delta Registered Installers, Oaks Damp Proofing Co Ltd were engaged to assist on an exciting new development, in London.  The project scope was to offer waterproofing design and installation to a warehouse facility.  The 33,000 square foot structure would offer 107 separate dwellings once complete.  The project requirements sought for a sympathetic renovation of an existing basement and back of house comms areas.

When it comes to structures, waterproofing and retrofitting waterproofing solutions is a critical element for protecting a structure and preserving its value.  Poor waterproofing (from design to installation) can cause numerous issues.

As with new build projects, retrofitting waterproofing designs should incorporate BS 8102:2022.  Protection of below ground structures against water ingress. Code of practice.

Delta’s trusted Technical Team were on hand to offer advice and guidance throughout the project.  There’s no one-size-fits-all when it comes to waterproofing design.  Working with the Architect, Main Contractor and client, Delta’s robust design was tailored precisely to the project requirements.

When specifying a retrofitted waterproofing solution, considerations should include but not limit to contamination of site, head heights, retaining walls.

Basements vary in head height, length, and width. When retrofitting basements, head height is often restricted. If a basement has a low head height, options of either raising the ceiling level or lowering the floor are open.  It should be noted that planning permission maybe required if raising ceiling levels or lowering floor levels.


A ‘Type C’ Waterproofing System was selected as a maintainable waterproofing solution to the existing basement to ensure a Grade 3 habitable environment was achieved.

A Delta Type C, waterproofing system was considered the most reliable and maintainable approach to the project.  In principle a cavity drained waterproofing solution allows moisture or running water to travel behind the membrane within a controlled drainage system.  A cavity drained system requires minimal preparation and disturbance to an existing substrate.

Due to a lack of head height on this project and options being limited on not raising ceiling levels or lowering floor levels, to maximise space, a complementary system of Delta’s PT 3mm membrane, FM membrane and Koster VAPlite was specified.

Prior to the installation of the Type C System, all construction joints were sealed.  Due to the nature of concrete, structures are often constructed in divided sections using joints. The key function of sealing joints prior to the application of the waterproofing solution is to create a secure waterproof barrier and to minimize potential structural weak points which allow for water ingress.

Using Koster Repair Mortar Plus Oaks created, coved fillets at the soffit/wall and wall/floor junctions.  Coved fillets help in lowering stress concentration and help to protect this vulnerable area from water and moisture penetration.

Perimeter drainage channels were sited within rebates in the basement floor, allowing for suitable drainage of any water ingress being diverted to suitable discharge points, in this case 2 of Delta’s V4 sump pumps.

Oaks applied a layer Koster NB1 prior to an application of Koster VAPlite to the entire floor area.  Koster VAPlite is a one-coat, membrane-forming, moisture vapor control system consisting of a unique combination of epoxy resins and other compounds formulated to prevent floor covering failures on concrete slabs with elevated levels of moisture.  An application of Koster SL Premium completed the waterproofing system to offer a stable, hard-wearing, and trafficable surface.

Before installation of the Delta Type C, membranes, all new concrete was treated with Koster Polysil TG 500 anti-lime inhibiter to seal the surfaces and reduce the leaching of ‘free lime’ which could cause blockages behind the membranes.

After the Type C System was installed the all-important integrity testing was undertaken to exercise the waterproofing system in worst case scenario.

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