Screwing metal roof is simply meaning to attach 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 metal roof in correct way is a crucial matter, including how it is screwed to your house. Take an example of standing seam roof, which has flat and broad panels that interlock by protrusion to give 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 panels of standing seam roof are fastened by using screw and being concealed to make it last far longer and prevent it to be failed.
There are different metals or metal combinations of screw that can give 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 flat side of the panel, instead of the top of rib part. This way, the metal roof will be attached securely with the underneath solid wood layer, so it can be fastened by the screws tightly.
The purpose of placing screws on flat part is to provide good seal, because otherwise, there is a chance of the rib tilt and then make the screw hole loose. If the hole is becoming loose and larger than its washer, the seal will be broken because.
Another reason to not put the screw on top of rib part is because there’s a high potential of screw being pulled by strong wind. Placing it on the flat side will be strategic to create stiff structure.
Screw Pattern for Corrugated Metal Roofing
Metal roof screw pattern or the distance between each screw is measured according o the layer underneath. There are two types of layer 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 every purlin’s line. It is also possible to fasten it at every other purlin if the purlins are very close to each other.
Screw pattern for metal roofing on top of solid wood
The metal roof screw pattern that sit on top of wooden substrate is typically should be consulted with roofing engineer. The thumb rule is that when you are in doubt, 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 pattern.
However, as 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.