A damaging hail storm struck Brisbane at about 6 pm on Thursday 19 May 2006.
The size of the hail stones in this storm generally ranged from very small up to 15 mm diameter. Wind driven hailstones of this size can severely damage an unsealed asbestos cement roof. From the air, the path of the storm could be tracked across Brisbane by following the trail of white unsealed asbestos cement roofs. These unsealed asbestos cement roofs were stripped clean by the hail and were left white because the previously black weathered surface of the unsealed roof sheeting was hail blaster off the roof.
WHAT IS THE BLACK GUNGE AND WHERE DID IT GO?
The black appearance of an old asbestos cement roof is created by the growth of lichens, mosses and other organic materials combined with atmospheric dust and pollutants.
Over time this culture is fed by rain water and literally grow like a garden. The roots of the plants in this garden penetrate the surface of the UNSEALED asbestos cement roof and small particles of cement are constantly dislodged and separated from the asbestos fibres. This results in a steady deterioration of the surface of the asbestos cement mixture. The resultant debris (including asbestos fibres) is deposited by rainwater into guttering, drainage systems and water collection tanks.
The end result was that, many workplaces required urgent decontamination to remove the potential hazard posed by asbestos fibres. In some cases workplaces had to be shut-down while the clean-up was conducted!
Over time repeated abrasive action of this sort can measurably reduce the thickness of the roof leaving it vulnerable to cracking.
WHAT TYPE OF ASBESTOS?Â
Corrugated asbestos cement roof sheeting is commonly comprised of a mixture of cement (approx. 85%) and asbestos fibre (approx. 15%). Analysis has shown that the majority of asbestos cement roof sheeting in Queensland contains Chrysotile (white) asbestos but older roof sheeting can contain Amosite (brown or grey) or Crocidolite (blue) asbestos or a mixture of asbestos types.
WHAT HAPPENED TO ASBESTOS CEMENT ROOF SHEETING THAT HAD BEEN PREVIOUSLY SEALED BY RESTYLE?
NOTHING!!! THE RESTYLE EPOXY ENCAPSULATION SYSTEM WITHSTOOD THE BLAST!
An inspection of one asbestos cement roof that had been sealed in May 1998 with the Restyle Epoxy Encapsulation System showed that the Restyle Epoxy Encapsulation System had withstood the abrasive action of the hailstones with only minor chipping evident. There was no evidence of asbestos containing debris in guttering!
Following the storm an inspection was conducted on three asbestos cement roofs installed on residential housing in the same street in the northern suburbs of Brisbane.
This roof was treated with Restyle Epoxy Encapsulation in May 1998. There was no visible abrasion and the coating remained in good condition. The distribution of asbestos contaminated material had been prevented.
This roof had been painted with another company’s paint process that involved chemical precleaning and standard water based priming. The coating was visibly chipped off by the hail. While debris was evident in guttering, the distribution of asbestos contaminated material had been limited.
Not previously painted. The hail stripped the entire roof leaving the roof with the typically white spotted appearance. Significant amounts of asbestos containing debris was dislodged and distributed in the guttering and surrounding areas.
The seven-year-old Restyle Epoxy Encapsulation System withstood the abrasive action of the hail and prevented the distribution of asbestos containing debris. Under the attack of wind-driven 5 to 15 mm hail stones, the Restyle Epoxy Encapsulation System outperformed another paint coating in preserving the integrity and appearance of the roof.