Make it safe first
Keep people and pets away from any fragments on the ground. Do not sweep, vacuum or hose them. If pieces have fallen, cover them with a sheet of polythene weighted at the edges and leave them for the contractor.
Do not climb on it
Cement sheets can be brittle with age and moss makes them slippery. A fall through a garage roof is a serious injury. Take photos from the ground or a window instead.
Stop the water, not the roof
If water is coming in, protect what is inside. A temporary tarp can be fixed from inside the garage with batten, but do not drill or break the sheets. A proper fix is a replacement roof, not a patch.
Get it looked at
Send photos of the roof and the inside of the garage, with your postcode. A contractor will tell you whether the damage is cosmetic or structural and give you a price. Storm damage may be covered by home insurance, so check your policy and keep the photos.
Quick answers
Is a cracked asbestos roof dangerous?
A crack alone is a lower risk than a broken piece falling or being disturbed, but it is a reason to act.
Can I patch a leak with sealant?
It may hold for a while. It is not a long-term fix and should not involve drilling or scraping.
Will insurance pay?
Sometimes for storm damage, rarely for age and wear. Read the policy.
How urgent is it?
Active leaks and loose sheets are urgent. Say so in your enquiry.