something to seal a Garage roof (Ludlow SY8)

Hi we have got a garage with an asbestos / concrete corrugated sheet roof
the joints are leaking and some of the sheets have gone porous
has anyone got anything I can use to seal it?
roof seal - Bitumen paint - flashing strip
part or whole tins or ends of rolls flashing
we want to seal it from the inside

thank you in advance

       
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