Stuart Hicks from cold-applied liquid waterproofing specialist, Kemper System, explains the challenges surrounding the roof renovation of a busy London hospital.
Lewisham Hospital is an acute district general hospital run by Lewisham and Greenwich NHS Trust. The history of the site where the current building stands dates back to 1612 when it became a workhouse for the sick and poor in the area. When the Lewisham Workhouse became overcrowded, a new building was erected at the site in 1817 to meet demand.
A separate infirmary was then built in 1892 – this building now houses the hospital’s pathology department at the site today. Following the formation of the National Health Service (NHS) in 1948, the hospital continued to expand with new buildings opening in the 1950s and 1960s. Today, Lewisham Hospital offers a wide range of specialist services and gained university status in 1997.
The hospital has served as a vital resource for the community for many years, and the Lewisham and Greenwich NHS Trust realised some of its buildings were in need of repair.
The existing felt roof above the main building and outpatient department of the hospital had failed, and Kemper System’s Kemperol 2K-PUR system was selected to provide a durable and long-lasting waterproofing solution.
This article looks at why Kemper System was specified, the benefits of a cold-applied liquid waterproofing solution for this particular project, and how installation challenges on site were faced and resolved by contractor, Noble House Services (UK) Ltd.
Because of the nature of the building, there was a need to ensure the project avoided any disruption or nuisance to staff and patients in the unit or the surrounding wards. Kemperol 2K-PUR is a completely odourless cold-applied solution and was used to refurbish the 1600m² roof area.
Noble House Services (UK) Ltd first cleared the roof of all redundant services, removing as much as feasibly possible without causing disruption to the running of the hospital. The existing asphalt roof was then cleaned and the Kemperol 2K-PUR resin was applied directly to the existing roof coverings in a single wet-on-wet process.
Reinforcement fleece was laid directly onto the first application of wet resin, immediately followed by more resin on top to ensure complete saturation of the reinforcement fleece. This provided visible assurance the correct amount of resin had been used throughout, and a consistent depth of coverage and membrane thickness is achieved. Once cured, the system forms a seamless, elastomeric waterproof membrane that cannot delaminate, is UV stable, and creates a strong bond directly to the substrate.
Contractors then installed an inverted insulation scheme comprising a closed-cell, 160mm extruded polystyrene (XPS) insulation board, concrete faced 50mm insulation board, followed by paving slabs to the perimeters to add additional ballast to the roof build-up.
The roof area had a number of complexities with many ventilation outlets, up-and-over staircases and walkways, steel beams supporting the units on the roof, as well as upstands and roof hatches for access. Because Kemper’s waterproofing system is roller-applied, operatives could easily install the resin underneath the units and around the complex roof structure.
The solvent-free and odourless qualities of the Kemperol system also meant minimum disruption at the hospital throughout the application process. No hot works were required as part of the refurbishment, further reducing potential health and safety risks, with no wait time between applications of resin.
A sustainable solution
Thanks to the speed of application of the Kemperol 2K-PUR system, vital services provided at the hospital were able to continue with little disruption to staff or visitors.
The roof area which needed attention was above the main entrance as well as Radiology, Cardiology and MRI departments – all very important sections of the hospital building. Refurbishment of the roof using Kemperol and the inverted insulation scheme has provided higher thermal performance and energy saving benefits for the building. We are extremely pleased with the finished project which was completed on time and within budget.
Contractors were able to install the Kemperol liquid waterproofing system quickly and safely, without the fire risk of hot works, despite the complexity of the roof area.
Gerry Ogborn from Noble House Services (UK) Ltd added: “We didn’t experience any issues when installing Kemperol 2K-PUR. This project could have presented a number of problems and time delays if an alternative roofing material was specified, but it was not only easy to transport with minimal materials and apparatus to carry, but the liquid-applied resin meant we could get underneath and around the complex roof structure and detailing with ease to provide a seamless waterproofing solution.”