Castlemead House in the London Borough of Southwark was undergoing an internal refurbishment when Paragon Interserve called in roofing contractor Hambro Roofing to carry out repairs to the roof. It soon became clear that the condition of the existing felt roof was too poor for remediation with patch repairs, leading to the installation of a new SikaBit roofing system from Sika as an overlay, providing a like-for-like appearance while upgrading the performance and service life of the existing roof covering.
Craig Smith from Sika explains: “The client was keen that any roof refurbishment should be carried out using a Safe2Torch reinforced bitumen membrane, but it was clear that there was an opportunity to upgrade the existing system with more advanced bitumen technology. SikaBit’s best-of-both-worlds SBS and APAO hybrid bitumen technology provided the ideal solution to achieve consistency of specification while enhancing the roof build-up.
“The system was specified as part of a warm roof build-up, which also included SikaTherm tapered insulation, to both enhance thermal performance and improve drainage by introducing falls and directing direct run-off water to existing drainage outlets.”
Hambro Roofing proposed using the SikaBit system for the project after seeing the advantages of the SBS/APAO hybrid technology, which has been specially-formulated by Sika for the UK market and Safe2Torch compliance. The system combines the flexibility and tensile strength benefits of SBS bitumen with the hardwearing properties and U/V stability of APAO.
After cleaning and preparing the existing roof surface, the Hambro Roofing team installed an S.VAP HD SA self-adhesive air & vapour control layer (AVCL). The roof was then coated with Sika Primer 600, followed by the installation of the tapered insulation scheme.
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 sheet in the Safe2Torch zones, before completing the project by installing SikaBit SA940 G self-adhesive cap sheet in all the torch exclusion zones.
Mark Robinson, contracts manager at Hambro Roofing, says: “The SikaBit system offered us the flexibility to address unforeseen challenges with the roof. For example, we discovered during the project that operational hot water pipes were running through a central wall at roof level. We were able to box in the pipes and dress the SikaBit system to the boxed area, ensuring it was completely watertight.
“We were extremely impressed with the SikaBit Safe2Torch system and how it performed on this project in delivering a great finish across the whole roof area.”