The nature and quality of iron sheets in accordance to the slope/angle of roof design matters to its durability and leakage, however its not desirable to use versatile or v-shape iron sheets when doing flat roof covering, this is because low water speed on them and their inabilty to restore shape when any force is put on tbem, if its so try increasing on the gradient/angle of the roof, for safer out comes, ordinary iron sheets are more fit for better results, for one to enjoy good stay for life in flat roofs, it must be giving zero leakages and strongly supporting the ceiling, to achieve this, find the right person to fix your roof, for more contact +