Screwing metal roofs means attaching metal panels to the building structure – be it wood substrates or steel material. Metal roof screw pattern, material, size, or design will depend on the building owner and the professional builder, according to the applications and the desired results.
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Metal Roof Screw Pattern
Installing a metal roof incorrectly is crucial, including how it is screwed to your house. Take an example of a standing seam roof with flat and broad panels that interlock by protrusion to give the roofing system a lot of strength.
Read also: Things that You Must Know About Metal Roofs
Being made from copper, aluminum, zinc, or galvanized steel, the standing seam roof panels are fastened using screws and concealed to make them last far longer and prevent them from being failed.
There are different metals or metal combinations of screws that can give a different result. The standard ones are made mostly from carbon steel and coated by corrosion resistance material.
Meanwhile, the metal roof screw pattern will depend on the number of fasteners used that also depends on the purlin spacing and panel profile. Below are two easy and common formulas you can use 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 sq. ft.)
For example: 20 roofing sq. x 80 screws = 1,600 screws
Where to Place Screws on Metal Roofing
If you’re using corrugated metal roofing, it is recommended to install the screw on the panel’s flat side instead of the top of the rib part. This way, the metal roof will be attached securely with the underneath solid wood layer to be fastened by the screws tightly.
The purpose of placing screws on the flat part is to provide a good seal because otherwise, there is a chance of the rib tilt and then make the screw hole lose. If the hole is becoming 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 that there’s a 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 too 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. For metal purlins, the roofing professional will use a chart to determine the correct spacing. However, the common rule is to attach the screw-on to every purlin’s line. It is also possible to fasten it at every other purlin if the purlins are very close.
Screw pattern for metal roofing on top of solid wood
The metal roof screw pattern that sits on top of the wooden substrate is typical should be consulted with the roofing engineer. When you are in doubt, the thumb rule is that using more attachment is better than the lack of it.
In general, there are plenty of helpful diagrams and videos on the internet you can get 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.