Poorly designed internal gutters rebuilt with deeper custom flashings and larger outlets, over two businesses operating below.
A commercial roof replacement in Henderson, West Auckland, on a building with two businesses operating underneath.
The existing roof was an old-style concealed-fix roof, and it was old and deteriorated. The internal gutters were poorly designed. They had been sealed and riveted to the underside of the roofing sheets, and had caused consistent problems over the years. The building also has an unconventional parapet wall design, with the parapets built in different sections.
The new roof is 0.55 BMT COLORCOTE® ZinaCore BB900 in Sandstone Grey, roll-formed by Dimond Roofing, over Thermakraft Thermabar 397 underlay.
With two businesses operating below, health and safety was critical. Electricians came in to disconnect the power and lower the main power cables.
The roof sheets are over 17 metres long. It took the full team to lay the underlay straight and to handle the sheets, and we used a crane to lift the old roofing off and the new sheets on.
Builders came in to help rebuild the internal gutter areas. We designed custom flashings to give the internal gutters more depth, with much larger outlets so they drain properly. Because the parapet walls are wide, we used standing seam style detailing for the back tray flashings around the internal gutters.
The building and its parapets are long, so we had to allow for expansion and contraction. We used grab flashings under the parapet flashings, so the parapet flashings are concealed-fixed and can expand and contract. Around the front of the building there were some unusually shaped areas, and we designed custom flashings for those as well.
The job needed a lot of custom design and planning. We're happy with how it looks, and the new roof and gutters have improved the roof's durability and how well it drains.
