Kemper System’s cold-applied liquid waterproofing solution has been specified for a multi-million-pound extension at St John’s and St Elizabeth (HJE) Hospital in the St John’s Wood area of London.

The £35m new build development has created six, hi-tech theatres and a day case suite which is one of the most modern in the UK. The extension also includes a new admissions lounge, imaging department, consultant rooms and an expanded Urgent Care Clinic.

A total of 9,060sqm of Kemper System’s Kemperol 2K-PUR solvent-free and odourless waterproofing membrane has been applied beneath the building’s green roof, onto a pedestrian trafficked walkway, the lower roof area and a plant roof area. The cold-applied solution was installed by London-based Ridgewell Flat Roofing Ltd.

Contractors had a strict timescale to adhere to, meaning a quick and easy application solution was required to complete the job.

Because of the location of the new build extension, adjacent to an occupied hospital building at HJE, the solvent-free and odourless qualities of the Kemperol system meant minimum disruption at the hospital throughout the application process. No hot works were required as part of the project, further reducing potential health and safety risks, and meaning no wait times were needed between applications of resin.

Once cured, the system forms a seamless, elastomeric waterproof membrane that cannot delaminate, is UV stable, and creates a sturdy bond directly to the substrate.

Additionally, the plant roof area had a number of complexities with many ventilation outlets and air conditioning units, and because Kemper’s waterproofing system is roller-applied, operatives could easily install the resin underneath the units and around the complex roof structure.

Ben Ridgewell, managing director of Ridgewell Flat Roofing, said: “We have used Kemper System for many years, and the cold-applied solution was perfect for this prestigious project because it is so versatile. We could apply the system to each of the different roof and walkway areas with ease without having to switch roofing materials.

“Kemper System once again delivered on such a complex project, which presented winter working challenges, specifically with high winds at times. Large expanses of sheeting material would have not have been practical or safe on site, so a roller applied liquid waterproofing solution was the best for this project. We were extremely happy with the results, and so is the end client.”

Victoria Ramwell, commercial manager at Kemper System, added: “We are delighted that our solution was specified for such a fantastic project, showcasing its versatility on both new build and refurbishment works. Our Kemperol 2K-PUR solution is manufactured using an 80 per cent castor-oil formula derived from sustainable sources. The system has stood the test of time with a proven 20-year track record and continues to be one of the most popular and sought-after systems for all sorts of projects.”

St John & St Elizabeth Hospital, which is in its 165th year of operation, is an independent charitable hospital. All treatments that take place in the hospital help fund the on-site St John’s Hospice, which provides free palliative care to more than 4,500 people and their families each year, across seven boroughs. The hospital provides surgery, medical care, outpatient, and diagnostic services for children, young people, and adults.

The new building, which is opening in planned stages throughout 2022, follows a recent £3.5 million ward refurbishment.