The Dunedin Public Art Gallery needed a new roof. The existing one was a mixture of profiled metal and membrane installed on both ply and concrete substrates. The building had serious condensation issues and the old butyl membrane seams were letting in water, thus deeming the roof-mounted plant susceptible to collapsing through the decaying timber substrate.
The Dunedin City Council set a strict brief for the Art Gallery’s new roof — it needed to improve both weather tightness and thermal efficiency. It was also paramount that the new roofing solution be installed without disrupting or removing the items housed in the building and that the building remained operational.
Viking WarmSpan was specified for this reason, but also because the lightweight nature of Viking WarmSpan would significantly reduce the stress on the building without compromising its structural integrity.
Viking WarmSpan is a BRANZ appraised, warm-roof-on-steel roofing system designed for low-sloped roofs. It has been engineered in New Zealand and is one of the country’s simplest and most energy-efficient warm roof systems. The full proprietary system is made up of three components:
- A wide-spanning steel tray roof deck that also forms the vapour barrier
- KingSpan Polyisocyanurate rigid insulation panels adhered on top, waterproofed with
- One of Viking’s Membrane Systems
The first stage was to remove, recycle, and replace the 550m² of tired rubber membrane as well as the steel roofs.
Viking WarmSpan was installed, incorporating its trapezoidal steel substrate, integrated vapour barrier, and two layers of 50mm polyiso insulation to achieve a continuous R-rating of R4. Heat-weldable Viking Enviroclad TPO membrane was installed in 3m wide rolls, ensuring no end-laps as each roll extended the full width of the roof.
Unlike plywood or concrete substrates, the steel substrate made the roof 100% watertight from the early stages and a permanent roof safety system was also installed to the perimeter.
The workmanship of the Viking Approved Applicator was put to the test when 15 students climbed from a neighbouring building, jumped the razor-wire perimeter and had a party on the newly installed roof. The roof survived comfortably — the robust nature of Viking’s materials, along with the quality of workmanship, proving to be a winning durable combination.