The 3,000 m2 International Electric Maintenance Depot of DB Cargo UK has been constantly in use since 1960 and the roof was showing its age.
Glass rooflights made up 40 per cent of the roof area with the remainder covered by a built-up felt system mounted on a galvanised steel deck. While the deck was still in good condition, time had caused the felt to degrade so that the roof leaked badly.
With lots of constraints around site access, contractors GL Contracts proposed re-roofing by overlaying the existing roof.
In developing the solution, GL Contracts was supported by SIG Design and Technology. Together they worked up a solution using IKO’s Armourplan PSG Fleece Backed PVC membrane bonded to heavy duty 18 mm OSB board, which in turn was mechanically fixed to the existing roof structure.
The use of an OSB overlay allowed the existing roof to remain in place. It was attached by screwing down through the existing roof and into its steel subframe. Armourplan was then bonded to the OSB board using Armourplan Spectrabond Low Foaming PU adhesive. Because Armourplan is gas-permeable, any moisture remaining in the original roof will be able to evaporate over time.
The rooflights were to be retained so SIG Design and Technology developed a bespoke membrane detail to provide a watertight seal around them.
With full materials warranties provided by SIG this was a pragmatic solution to a complex renovation challenge.