ReRoofing of Office Building  Posted 09.03.04                hover your mouse curser over the photo for the text

This early 1960's Office Building  originally had a Mastic Asphalt roof  25mm thick laid over a lightweight pumice based screed on concrete.
During refurbishment in the mid 1970's a second layer of mastic asphalt 12mm thick was overlaid to extend the life of the roof..
During the ensuing 30 years very little maintenance was carried out until 1998 and due to thermal expansion and contraction the 2nd layer gradually failed and water became trapped between the 2 layers, causing major blistering.
A 3rd overlay was not possible or recommended as the trapped moisture could not be removed.
The only solution was to remove the 2nd layer and repair the original roof, before applying a new torchon membrane.
The building was fully occupied during the re roofing and the work carried out during the wettest local summer in  recorded weather history.
The 2nd layer of mastic asphalt , west wing The 2nd layer of mastic asphalt , centre
The 2nd layer of mastic asphalt , east wing An example of the thermal expansion and contraction of the 2nd layer of mastic asphalt
An example of the trapped moisture causing blistering between the 1st and 2nd layers An example of thermal movement and trapped moisture combined
The second layer is removed Removing the 2nd layer, some parts were fully bonded, at the bay laps
Craning the materials to the rooftop The disposal chute for the debris at the rear of the building
Warming up and removing the fully bonded strip areas Warming up and removing the fully bonded strip areas
The first area prepared, primed with bitumen pimer and ready for torchon membrane some badly wrinkled areas had to be flushed off with a cold mastic plaster compound to level out the area
Just one of the many wet and windy days during the work Applying the 4mm thick SBS Torchon membrane, in this area over a perforated vent sheet to allow the escape of any residual moisture from the mastic plaster skim over
A view of the centre roof area with the new Torchon membrane A view of the west wing roof area with the new Torchon membrane
One of the pipe penetrations through the roof, this one with a cricket flange to divert surface water around the pipe A large round chimney vent from the office kitchen below (Vent Hat removed)
The centre roof area and west wing after application of the Bituminous Aluminium Paint coating The west wing roof area after application of the Bituminous Aluminium Paint coating
This corner hasd some residual moisture trapped in the pumice screed below the original mastic asphalt, so a brether vent has been installed Another view of the completed roof, here comes the rain again!!!!!!