The Sika-Trocal type S membrane has been installed as part of the refurbishment project at the northbound carriageway of the Blackwall Tunnel. Specialist contractors Robertson roofing installed a layer of Sika-Trocal S-felt type A protection fleece, which was mechanically fixed using Sika-Trocal laminated metal discs. This was followed by a layer of Sika-Trocal Type S 1.5mm thick light grey membrane welded to the Sika-Trocal laminated metal discs.
The Trocal detailing to the eight central individual triangular curved petal sections on each dome had to be designed to allow trouble free opening and closing. Each triangular petal section received a perimeter framing of rigid Trocal laminated metal edge profiles that lap into narrow fixed gutter channels at the petal abutments when closed. The rigid Trocal laminated metal edge profiles were designed to allow the individual petal section to open and close without snagging against each other and to ensure water tightness when closed.
The Sika-Trocal type S membrane was installed in a manner to ensure the layout of the flaps gave the best aesthetic appearance to the finished roof.