English to Polish Tech/Engineering Other Budowa dachów

So what are decramastic roof sheets?
They are galvanized steel pressed metal roofing sheet which were popular in the 1970's - 1980's as a roofing material. They were formed into the shape of 5 tiles and coated with a bitumen coating with a fine stone aggregate embedded in the coating. You can see in the photo the bitumen coating and their resemblance to a cement roof tile.

Why are they a bad choice in roofing material?
Decramastic roof sheets are renown for leaking and result is water damage in the roof cavity and on the ceiling of homes.
So what are the causes of this - Weathering, hail damage and careless foot traffic on the roof sheets. They are lightweight in nature and you can see in the photo above the crease and ding in the decramastic roof sheet. This is one of the major causes of the water leak. Foot traffic easily dings and creases the sheets causing water to be able to pass under the roof sheets and straight into the roof cavity.