Where to Place Screws on Metal Roofing? 3 Screw Positions

Metal roofing sheets can be used on roofing applications as well as wall sidings.

On metal roofing sheets, screws should always be installed on the crest corrugation or on the ribs. This rule of thumb goes the same no matter what roofing sheet material is used, metal or plastic. We all know that because of gravity, water and debris will always attempt to go the lowest point, so if the fastener is placed on the valley or lowest point, it will obstruct the flow of water and debris on their way to the gutter. If by chance the screws are improperly installed, the chance of leakage will definitely increase.

Since there are so many different types of roofing on the market, it will be much simpler to break it down into 3 screw positions:

1. middle/internal purlins.

2. external purlins.

3. overlapping areas.

Just as an example, for metal roofing sheets with continuous corrugations of the same pitch and depth, screws on the middle/internal purlins, end/external purlins and overlaps are normally placed as follows. There is also a slight difference between the fixing schedule in mild wind areas and high wind areas.

Mild wind areas:

End/External purlins – Fasteners are normally placed on the crown/crest corrugation of every other rib in the horizontal direction.

Middle/Internal Purlins – Fasteners are normally placed on the crown/crest corrugation of every second rib in the horizontal direction, and spaced evenly along the length of the rafter.

Overlaps – Overlapping areas have to be fixed down and also spaced evenly on the length of the sheet.

High wind areas:

End/External purlins – Fasteners are normally placed on the crown/crest corrugation of every rib in the horizontal direction.

Middle/Internal Purlins – Fasteners are normally placed on the crown/crest corrugation of every other rib in the horizontal direction, and spaced evenly along the length of the rafter. The spacing between every screw may be halved compared to mild wind area fastening for added strength.

Overlaps – High wind areas usually require overlapping two corrugations, on which both crests have to be fastened, and also along the length of both corrugation crests, spaced evenly along the length of the sheet.