Have you ever wondered why there is still a water leak around the screws even though screws with sealing washer under the screws head are used for the buildings (Self-drilling screws have a drill point at the end).

One of the reasons is how hard the roof installer applied with the screws in order to fix the sheets to the purlins. Using power drill tool with the suitable speed will give the proper capacity which may not split the sealing washer and deform the sheet (see the picture in the middle – correctly driven) and avoid rubber ring to slipIf you tighten screw until the washer is split (see the right picture – overdriven). If you loosen screw then will cause a gap between washer and screws (see the left picture – underdriven). Both overdriven and underdriven can cause water leak around screws and therefore selecting the screws are significant for the life expectant building.