Screwing metal roofs means attaching metal panels to the building structure – be it wood substrates or steel material. According to the applications and desired results, the metal roof screw pattern, material, size, or design will depend on the building owner and the professional builder.
Metal Roof Screw Pattern
Installing a metal roof incorrectly, including how it is screwed to your house, is crucial. Take an example of a standing seam roof with flat and broad panels that interlock by protrusion to give the roofing system strength.
Read also: Things that You Must Know About Metal Roofs
Made from copper, aluminum, zinc, or galvanized steel, the standing seam panels are fastened using screws and concealed to make them last far longer and prevent them from failing.
Different metals or metal combinations of screws can give a different result. The standard ones are made mostly from carbon steel and coated by corrosion-resistant material.
Meanwhile, the metal roof screw pattern will depend on the number of fasteners used, which also depends on the purlin spacing and panel profile. Below are two easy and common formulas to calculate screws for metal roofing.
- Measure the square footage of your roofing area and multiply the number by 80%.
For example: 2,000 sq. ft. x 80% = 1,600 screws
- Convert the extent of roofing area to roofing square (1 roofing sq. = 100 square feet)
For example: 20 roofing sq. x 80 screws = 1,600 screws
Where to Place Screws on Metal Roofing
If you’re using corrugated panel metal roofing, installing the screw on the panel’s flat side instead of the top of the rib part is recommended. This way, the metal roof will be attached securely with the underneath solid wood layer to be fastened by the screws tightly.
Placing screws on the flat part provides a good seal because otherwise, the rib tilt is possible and then make the screw hole lose. If the hole becomes loose and larger than its washer, the seal will be broken because.
Another reason not to put the screw on top of the rib part is the high potential of the screw being pulled by a strong wind. Placing it on the flat side will be strategic to create a stiff structure.
Screw Pattern for Corrugated Metal Roofing
Metal roof screw pattern or the distance between each screw is measured according to the layer underneath. There are two types of layers below metal roofing, metal purlins or solid wood substrate.
Screw pattern for metal roofing on top of metal purlins.
The distance depends on the steel’s thickness and the panel’s type. The roofing professional will use a chart to determine the correct spacing for metal purlins. However, the common rule is to attach the screw-on to every purlin’s line. It can be fastened at every other purlin if the purlins are close.
The spacing of the metal purlins beneath the roofing panels is a critical factor in determining the screw pattern. The distance between purlins will affect the number and spacing of screws required. Purlin spacing should adhere to engineering specifications and local building codes.
Hidden fastener systems are often chosen for their aesthetically pleasing appearance, providing a cleaner look without visible screws.
Screw pattern for metal roofing on top of solid wood
The metal roof screw pattern on top of the wooden substrate is typical and should be consulted with the roofing engineer. When you are in doubt, the thumb rule is that using more attachments is better than the lack of it.
There are plenty of helpful diagrams and videos on the internet to learn more about metal roof screw patterns.
However, as the roofing system is a rather complex and pivotal part of your house structure, it is always better to discuss or hand it over to professionals and experts.