After experiencing huge wind storms during the 90's (1990-1995) lot of research programmes were launched worldwide to investigate the reasons why so much roofs encountered severe damages like truss-wall failures or more frequently rood elements removals. This last issue seems to be less important for the security aspects but gives the insurance companies some nightmares when seeing the bill. Actually, it is more the number of damage occurrences that can drastically increase the (repairing) costs.