Now that the dangers to human health of asbestos exposure are widely known and reported it is likely that the owners of buildings with such roofs will want to prevent asbestos fibres escaping as the roof deteriorates. This can be done safely by sealing them with specialist products or cladding them with metal.
In fact, removing roofing material that is in good condition may pose a greater risk to health than sealing or cladding because the asbestos fibres (or dust) will be released as the sheets are broken up for removal.
It should be mentioned that asbestos comes in several forms – some of which are extremely hazardous to health and others much less so. Reports of the dangers of asbestos do not always make this distinction clear. White asbestos was most commonly used in asbestos cement for industrial roofing; it is less of a health hazard than other forms and, additionally, the asbestos fibres are encapsulated in the cement. Brown or blue asbestos on the other hand poses an extremely serious risk to health and can lead to asbestosis, mesothelioma or cancer.
So an undamaged roof made from asbestos cement sheets does not pose an immediate risk but the problem with roofs is that they are very often not easily accessible to check for damage so a building owner or manager may not be aware of a gradual deterioration in the state of the roof. It may only be when a building is sold to a new owner or re-let to a new tenant that a survey indicates the presence and condition of asbestos.
A common problem with asbestos roofing as it ages is that the sheets can crack. Indeed, finding out there is a problem with asbestos can often manifest itself initially as a leaking roof. But the question many building owners are concerned with is how long can they expect an asbestos cement roof to last?
The life of a roof naturally depends on various factors and it is impossible to give an exact figure because the expected lifetime can be affected by the position of the roof, the quality and type of the original workmanship, whether it has been well-maintained and many other factors. But in general an asbestos cement roof could be expected to last for 25 – 30 years in ideal conditions.
But this might not be a reasonable expectation for a roof exposed to extreme weather conditions that has been poorly maintained or repaired in the past and every roof should be viewed as an individual case. There is nothing to be gained from simply assuming it will last for 25 – 30 years; an inspection by an asbestos roof repair specialist is the only way to be sure of the condition of your industrial roofing and to obtain an accurate estimate of its life expectancy. If the asbestos roofing sheets are found to be damaged then sections of the roof, or maybe even the whole roof, will need to be encapsulated by sealing with a specialist product such as Fibroseal. For roofs in a very poor condition complete removal and replacement may be the only option.