Metal Roofing Fastener Guide: Complete Reference

Understanding Metal Roofing Fasteners

Metal roofing fasteners are specialized screws designed to secure metal roofing and siding panels to wood or steel framing. Unlike standard screws, metal roofing screws feature an integrated EPDM rubber washer that creates a weather-tight seal as the screw is driven. This seal must maintain its integrity through years of thermal cycling, UV exposure, and weather conditions — making fastener quality and installation technique critical for roof performance.

The screw itself is typically self-drilling, meaning it can penetrate the metal panel and the substrate below without pre-drilling. The drill point size must be appropriate for the total material thickness being fastened through — a point that's too small won't penetrate, while a point that's too large will create an oversized hole that the washer can't seal.

The head style is typically hex washer head, which provides a large bearing surface for the EPDM washer and allows driving with a standard hex driver bit. The head is painted to match the metal panel color, providing a clean, professional appearance with no visible contrasting fastener heads.

Types of Metal Roofing Fasteners

• Wood-grip screws: Self-drilling screws designed for fastening metal panels to wood framing
• Lap screws: Used to fasten overlapping panel edges together
• Roofing screws with EPDM washers: Standard fasteners for through-fastened metal roofing
• Stitch screws: Short screws used to fasten metal-to-metal panel overlaps
• Combination screws: Self-drilling screws that can penetrate both steel and wood
• Replacement screws: For replacing failed or corroded screws on existing roofs

EPDM Washers: The Key to Weather-Tightness

The EPDM rubber washer is the most critical component of a metal roofing screw. EPDM (ethylene propylene diene monomer) is a synthetic rubber that maintains its elasticity and sealing properties through years of UV exposure, temperature extremes, and weather. When the screw is driven, the washer compresses between the screw head and the metal panel, creating a weather-tight seal.

Quality EPDM washers are bonded to a metal backing plate that distributes the clamping force evenly across the washer surface. This prevents the washer from extruding or deforming under pressure, which could compromise the seal. Low-quality washers without metal backing can deform and fail prematurely, leading to roof leaks.

Proper installation is critical for washer performance. The screw should be driven straight, not at an angle, with just enough pressure to compress the washer to about 50% of its uncompressed thickness. Overdriving can cut the panel and damage the washer, while underdriving won't compress the washer enough to create a seal. Visual indicators of proper compression include the washer being visibly compressed but not extruding beyond the screw head edge.

Screw Length Selection

Selecting the right screw length is critical for proper fastening. The screw must be long enough to penetrate through the metal panel, any underlayment or insulation, and at least 1 inch into the wood framing below. For standard metal roofing installed directly over solid sheathing, a 1.5-inch to 2-inch screw is typically adequate. For metal roofing installed over purlins (without solid sheathing), longer screws may be needed to reach the purlin.

For metal siding installed over furring strips or hat channels, screw length depends on the thickness of the siding plus the gap plus the furring strip thickness, plus 1 inch of penetration. For steel-framed buildings, combination screws that can penetrate both the metal panel and the steel framing may be required.

Our team can help you calculate the correct screw length for your specific metal roofing or siding application, considering the panel thickness, substrate type, and required penetration depth. We stock metal roofing screws in lengths from 1 inch to 6 inches to accommodate virtually any application.

Color Matching

Color-matched metal roofing screws provide a clean, professional appearance with no visible contrasting fastener heads. The screw heads are painted with a durable paint that matches the metal panel color. We carry screws in colors that match popular metal panel colors from manufacturers like ABC, Everlast, and Metal Sales.

When ordering color-matched screws, it's important to specify the exact panel color name and manufacturer, as colors can vary slightly between manufacturers. If you have a sample of your metal panel, bring it to our store and we'll help you match the screw color. Using a closely-matched but not exact color can create a visible mismatch that detracts from the roof's appearance.

For applications where exact color matching isn't critical — like agricultural buildings, sheds, or non-visible roof areas — standard colors like white, brown, or galvanized may be more economical than custom-matched colors. Our team can help you select the most cost-effective color option for your specific application.

Common Installation Mistakes to Avoid

One of the most common installation mistakes is overdriving or underdriving screws. Overdriving cuts the metal panel, damages the EPDM washer, and can create a leak path. Underdriving doesn't compress the washer enough to create a seal. The solution is to use a screw gun with adjustable clutch or depth-sensing nose, or to develop a consistent feel for proper driving depth.

Another common mistake is driving screws at an angle rather than straight. Angled driving can cause the washer to seal on one side but not the other, creating a leak path. It can also cause the drill point to wander, potentially damaging the panel. Always position yourself so you can drive screws straight down into the panel.

Using the wrong screw type is another mistake. Wood-grip screws should not be used for steel-to-steel connections, and stitch screws should not be used for panel-to-wood connections. Always select the screw type appropriate for your specific application. Our team can help you identify the right screw type for your metal roofing or siding installation.