Castlemead is a social housing block in the London Borough of Southwark, located in the busy Camberwell Road area. The vacant building was undergoing an internal refurbishment project, delivered by fit out specialist, Paragon, and as part of these works the main contractor brought in roofing specialist, Hambro Roofing, to carry out some repairs to the existing felt roof. It quickly became apparent that the existing roof surface had reached the end of its service life and actually required a full refurbishment

SikaBit Castlemead project


The client wanted to use a Safe2Torch-compliant reinforced bitumen membrane (RBM) roofing system that could be installed as an overlay to the existing roof, providing a like-for-like appearance while upgrading the performance and service life of the existing roof covering. SikaBit’s best-of-both-world’s SBS and APAO hybrid bitumen technology provided the ideal solution to achieve consistency of specification while enhancing the roof build-up.

There was also a requirement to reduce the potential for standing water by introducing falls to the roof using a tapered insulation scheme to improve drainage and direct run-off water to existing drainage outlets.


Hambro Roofing suggested to Paragon that the roof should be refurbished with a RBM overlay and proposed the SikaBit system for the project due to the flexibility and tensile strength benefits of the SBS elements combined with the hardwearing properties and UV stability of APAO.

SikaBit’s technical team visited site to carry out a roof condition survey and develop a full technical specification, which included the Safe2Torch SikaBit system and SikaTherm tapered insulation.

The Hambro Roofing team cleaned and prepared the existing roof surface before installing an SVAP HD SA self-adhesive air & vapour control layer (AVCL), which has been specifically developed using SBS bitumen technology, an aluminium layer and a self-adhesive backing to provide a torch-free element of the SikaBit system. The roof was then coated with Sika Primer 600 followed by installation of the tapered insulation scheme.

The SikaBit SA730 fully self-adhered underlay was then installed onto the insulation layer and the Hambro Roofing team installed the torch-on SikaBit T940 G cap sheeet in the Safe2Torch zones, before completing the project by installing SikaBit SA940 G self-adhesive cap sheet in all the torch exclusion zones.

The SikaBit system offered Hambro Roofing the flexibility required to address unforeseen challenges with the roof. During the project, the contractor discovered that there were operational hot water pipes running through a central wall at roof level. The Hambro Roofing team was able to box in the pipes and then dressed the SikaBit system to the boxed area, ensuring it was completely watertight.

To complete the roof installation, Hambro Roofing installed a new GRP trim around the fascia, concealing the change in curb heights prompted by the tapered insulation.

"We were extremely impressed with the SikaBit Safe2Torch system and how it performed on this project. Thanks to SikaBit’s hybrid technology we were able to apply the correct heat to achieve a perfect bleed in the Safe2Torch areas while the self-adhesive membrane provided the same high quality of finish in the exclusion zones, delivering a great finish across the whole roof area." Mark Robinson, Contracts Manager at Hambro Roofing