Facelift for Historical Building

Challenge

Designed during the depression by architect Edmund Anscombe, the 71-year old building served as a centre to aid returned servicemen and women in their reintroduction to civilian life during World War II.

It also became a factory for the manufacture of prosthetic limbs for disfigured soldiers. Its flat roof had been waterproofed several times using a bitumen-based liquid membrane; the layers of which had become brittle and cracked over the decades and had started to leak water through to the old sarking beneath.

Three years prior to the roofing project taking place, the building struggled to attract a purchaser because of the perceived exorbitant costs associated with re-cladding the 1,300m2 leaking flat roof (with next to no pitch). A church group eventually purchased the building with a view to embarking on its refurbishment.

21 Hania St’s heritage classification by the Historic Places Trust meant that the Wellington City Council required a resource consent for any exterior work, with a view to keeping the building as close to the original design as possible.

Originally a quantity surveyor was commissioned to explore the option of pitching the roof for metal roofing which would require specially-designed, engineered fixings to the original structure. This proved too expensive and troublesome, and as the building was occupied, opening the roof up meant too much cost and disruption. So another option was explored which involved a three layer torch-on system with the base sheet being mechanically fastened. But Viking Roofspec put forward a better option…

Solution

The Property Manager Ian Kearney, eventually chose the Viking Enviroclad F.B.S. (fleece-backed system) for several reasons:

It is designed to go over old membranes without having to tear them up. This means; (i) minimal disruption - none of the building’s occupants would need to be re-located during the roofing process; (ii) labour and dumping costs would be saved, and; (iii) the local landfill would be saved from 1,300m2 of asphalt.
Removing all of the existing bitumen membrane in gutters. This allowed a more thorough inspection to take place in these key areas whilst drying out any potential dampness and replacement of rotten substrate.
Performing carpentry in a number of degraded areas including relining parapets, skylight plinths and new timber bracing for the high parapets.The Viking Approved Applicator then set about installing 1,300m2 of Enviroclad F.B.S. with its 3.6m x 30.4m (109.8m2) rolls and F.A.S.T. adhesive system.

An additional insurance policy was adopted of mechanically fastening “Piranha” plates with screws (aluminium discs with teeth on the underside to grip the membrane) through to the original sarking just in case the bond between the old asphalt and sarking substrate wasn’t as strong as perceived in some areas. These were installed at 300mm centres underneath the welded Laps, and at 1.8m centres throughout the middle of the sheet.

To allow any residual moisture in the sarking to escape, no expense was spared on venting the roof. One-way, pressure release vents were installed and flashed with proprietary TPO pipe seals.

Result

In short, the 71-year-old building’s roof had been given a “birthday”. The owners were thrilled with the transformation of their tired; leaking; ugly; charcoal; asphalt roof into a fully warranted; dove grey; cost-effective, but most importantly watertight roof that would prolong the life of this lovely old lady. They can have peace-of-mind seeing technical representatives from Viking Roofspec will be inspecting the roof not only post-installation, but on the 1st, 2nd, 5th, 10th and 15th years of the 20 year warranty period – all as part of the Viking Full System warranty process.