On 3/6/2016 12:52 PM, wrote:
These sheets are nothing but cardboard covered in bitumen. They sag with any weight of rain or snow on them and need bracing at 600mm intervals max. I did my son's garage last year and now it all needs replacing. Total rubbish!!

Not asbestos cement then. Sounds more like Onduline or other
equivalents. I did one 25 years ago and it is now about due for
replacing. Don't see why they should sag with rain unless there's no
slope! If you follow the manufacturer's spec they will support the
weight of a sensible adult, but you would not find me on an asbestos
cement roof without proper crawling boards.