The great ‘rain’ escape

When the former Auckland Central Remand Prison roof was leaking, it looked like a straight-forward fix using Enviroclad overlay and ventilations. Harsh winter weather, damp concrete substrates and an inability to use traditional fastenings meant that the project required a major rethink.

CALL THE PROFESSIONALS

Viking Roofspec won the tender issued by the Department of Corrections to fix the leaking roof of Mount Eden Corrections Facility. Topline Roofing was chosen to undertake the work.

Topline work closely with Viking Roofspec who distribute a wide range of Viking roofing materials and waterproofing systems for residential homes and the building industry. The integrity, professionalism and experience of Topline and Viking Roofspec ensures buildings stay dry, and rain stays out.

Remedial work required

The contractors were told that the existing leaky roof consisted of 3,500m² of Epiclad EPDM membrane, which had been installed on 100mm thick concrete screed. Whilst the Epiclad installation was tidy, it had some failings due to chemical issues with the European manufactured lap-tape. Parts of the concrete substrate were constantly soaked and in places there was no slope for dispersing rainwater. The work was scheduled during the winter months, and with Auckland’s unpredictable weather, it was unlikely that the team would get a long enough rain-free spell to dry out the large and damp substrate.

BACK TO THE DRAWING BOARD 

Topline had originally proposed an Enviroclad overlay with plenty of ventilation to extract the existing moisture in the substrate BUT, Enviroclad cannot be adhered on top of EPDM rubber. The teams at Topline and Viking Roofspec revised their initial thinking and suggested a traditional mechanical fastening specification. However, using this method meant that the concrete had to be at least 100mm in thickness to mechanically fasten Enviroclad over EPDM using 50mm fastenings. Topline tested the concrete thickness and it was less than 60mm, it was time for a different approach.

NEW TECHNOLOGY FROM THE US 

Time was running out for the project to be completed and traditional fastenings were not going to work The waterproofing manufacturer and their roofing contractor had to look beyond New Zealand and found the solution in America. Untried and untested in NZ, RhinoBond induction fastening technology was suggested as an alternative method of mechanically fastening the Enviroclad without penetrating the membrane.

A NEW TYPE OF WELDING TOOL

TPO-coated metal plates were fastened to the existing substrate in a continuous 750mm x 750mm grid. Enviroclad membrane was then laid over the plates. The RhinoBond system welding tool was placed above each membrane of the RhinoBond plates. The welding tool emitted an electro-magnetic charge through the membrane, activating the TPO coating on the surface of the plate below, resulting in a weld between the plate surface and the underside of the membrane. Weighted magnets were then placed over the plates to dissipate heat and ensure intimate contact between the bottom surface of the membrane and the integral hot-melt TPO coating on the plate’s surface. This resulted in a superb penetration-free weld.

Topline Roofing highly recommend RhinoBond: