As small and simple screws and fasteners are, this construction material plays a big role in your metal roof installation. There are problems that arise when screws are not properly installed. Most common are if screws are overdriven or over-tightened, it will puncture your metal which will eventually be your leak points and if your screws are underdriven or loose, it can’t hold your metal roof during heavy wind which at some point will tear. 

Knowing your screws 

A. Material 

1. Stainless Steel 

Stainless steel, also known as rustless steel, is an alloy from iron and several other elements like chromium, nickel, and carbon which is made to be more resistant to corrosion and creates a shiny reflective surface. Most stainless steel has different grades like Grade 304, Grade 316, and Grade 430 which are specialized to be resistant to corrosion. 

2. Silicone Bronze 

Silicone Bronze is a low-lead brass alloy that contains 96 percent of copper and other elements may be manganese, tin, iron, or zinc. They have excellent bearing and load capacity and superior corrosion resistance. 

3. Brass

Brass is a metal alloy made from copper and zinc but other elements can also be added like aluminum, iron, and manganese. They have high strength and ductility, which are soft metals, and are also high in corrosion resistance. 

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B. Coating 

1. Zinc

Zinc is the most common coating used for screws and fasteners as they give an attribute of rust resistance and are inexpensive compared to other coatings. This zinc coating can be clear, silver, or yellowish. Zinc coating is best for humid environments. 

2. Hot Dip Galvanized 

Hot Dip Galvanized provides a thicker layer of zinc on the screw or fasteners which makes them more rust or corrosion-resistant, Due to its thickness, it is not compatible with most of the nuts. This hot-dip galvanized coating is best used in outdoor environments, especially in the coastal area where salt is present in the air. 

3. Chrome-Plated or Nickel Plated 

Chrome-Plated or Nickel Plated Coating has attributes of high resistance to rust or corrosion but is much more expensive. This is usually chosen for its appearance and its shiny finish. 

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C. Length 

The length of the screw and fastener starts the underside of the head to its drill point and sealing washers. 

D. Thread count per inch 

Thread count per inch is the count of thread per inch measured along the length of the screw or fastener. 

E. Drill Point Style

1. Self Drilling Screws 

Self Drilling Screws are known for their pointed drill-shaped point, this is in order to drill into materials like wood and metal, such as soft metals, without the need of pre-drilling the holes. 

2. Self Tapping Screws 

Self Tapping Screws, from the word itself, have the ability to tap a thread into the material like wood, bricks, or metal. They need pre-drilled holes before installation but because of their tapping action, it can provide more fastening ability. 

3. Self Piercing Screws

Self Piercing Screws have a sharp tip in order to “pierce” through the material like wood or even a thick gauge of metal, able to create threads as you install the screws. Because of its sharp edge, it does not need a pre-drilled hole before installation. 

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F. Screw or Fastener Heads

There are many screws or fasteners that you can match with a wide variety of screwdrivers. 

1. Flat Head
2. Button Head
3. Round Head
4. Hex Head
5. Oval Head
6. Pan Head
7. Socket Head