Best Screws to Use for Metal Roofing

Choosing the right screws for metal roofing affects durability, weather resistance, and leak prevention. This guide covers screw types, coatings, head styles, lengths, installation techniques, and maintenance to help ensure a long-lasting metal roof. Correct fastener selection prevents corrosion and roof failure.

Question	Short Answer
Best Screw Type	Self-drilling (tek) screws with neoprene washer
Material/Coating	Stainless steel or Class 3/4 galvanized with painted finish
Head Style	Hex washer head or pancake with EPDM washer
Typical Length	1/2″ to 2″ depending on substrate thickness

Types Of Screws For Metal Roofing

For metal roofing, the most common choices are self-drilling (TEK) screws and self-tapping screws. Self-drilling screws have a drill-like tip that eliminates the need for pre-drilling and speeds installation on metal-to-metal assemblies. Self-tapping screws are used when fastening metal to wood or when pre-drilling is preferred. Both types are widely used in residential and commercial metal roofing applications.

Materials And Coatings

Corrosion resistance is critical for roof fasteners. Stainless steel (304 or 316) offers the best corrosion resistance, especially near coastal areas. For cost-effective options, use carbon steel screws with high-quality galvanization such as G185 or Class 3/4 coatings and a factory-painted finish that matches the roof. Avoid plain carbon steel without protective coatings.

Head Styles And Washers

Hex washer head screws are the industry standard for metal roofing because they provide strong torque capability and a large bearing surface. Pancake (low-profile) heads are used for metal panels where a lower profile is desired. All roof screws used on metal panels should include a bonded EPDM or neoprene washer to seal around the fastener and prevent leaks.

Screw Diameters, Lengths, And Thread Types

Common diameters for metal roofing screws are #10 and #14. Length selection depends on panel and substrate thickness: typically, screws should penetrate the substrate at least 3/8″ to 1/2″. For metal-to-wood, add panel thickness plus wood thickness; for metal-to-metal, ensure sufficient grip through the backing metal. Fine-thread screws are better for metal-to-metal; coarse-thread screws are better for metal-to-wood.

Choosing The Right Screw For Panel Types

Standing seam panels often use concealed clips and require stainless or specialty fasteners, while exposed-fastener panels use screw-fastened crowns or flats. For corrugated or ribbed panels, use screws sized to the rib and seated on the flat area with washer contact. Match screw head and washer dimensions to the panel profile to ensure a watertight seal.

Fastener Placement And Spacing

Fastener patterns vary by panel, wind load, and manufacturer instructions. Typical spacing ranges from 6″ to 24″ on center along eaves and ridges, with closer spacing in high-wind zones. Follow panel manufacturer specifications and local building codes. Improper spacing or missed end laps are common causes of roof failure.

Installation Best Practices

Use a calibrated clutch on the drill driver to avoid overdriving screws, which can crush the washer or strip threads. Pre-drill clip holes for standing seam where required. Drive screws perpendicular to the roof surface to ensure washer compression is uniform. Never overtighten; snug to compress the washer without distorting it.

Tools And Accessories

Essential tools include an adjustable torque-controlled screw gun, hex socket bits, magnetic bit holders, and safety equipment. Use a depth-limiting coupling if available. For long runs, consider a collated screw gun to speed installation. Using the correct driver bit size reduces cam-out and stripped heads.

Corrosion Considerations And Galvanic Compatibility

Mixing dissimilar metals can cause galvanic corrosion. Avoid using carbon steel screws with aluminum panels unless there is a protective barrier or compatible coating. Stainless steel fasteners are safest with most metals. Always consult the panel manufacturer’s compatibility chart to prevent accelerated corrosion.

Sealing And Leak Prevention

Washers provide the primary seal around screws, but additional sealing may be needed at overlaps, penetrations, and flashing. Use butyl or EPDM closure strips at eaves and ridges and compatible sealants for trim. Periodic inspection of washers and sealants reduces the likelihood of leaks over the roof’s lifespan.

Maintenance And Replacement

Screws can back out over time due to thermal cycling and building movement. Inspect roofs annually and after severe storms. Replace screws with damaged heads, crushed washers, or corrosion. When re-fastening, use the same material and coating to maintain compatibility. Regular maintenance extends roof life and preserves warranty coverage.

Cost Considerations And Where To Buy

Stainless steel screws cost more than galvanized options but provide superior longevity and lower lifecycle costs, especially in coastal or industrial environments. Purchase from reputable suppliers or directly from panel manufacturers to ensure correct specs. Bulk purchases reduce per-piece costs for large projects. Balance upfront cost with expected performance and warranty requirements.

Common Mistakes To Avoid

• Overdriving screws which damages washers and panels.
• Using incorrect screw length that fails to engage substrate properly.
• Mixing incompatible metals causing galvanic corrosion.
• Skipping manufacturer fastener specifications which may void warranties.

Sample Fastener Selection Guide

Application	Recommended Screw	Material
Metal Panel To Wood Purlin	#12 Coarse Thread TEK With Washer, 1″–2″	G185 Galvanized Or 304 SS
Metal Panel To Metal Substrate	#12 Fine Thread Self-Drilling TEK, 3/4″–1-1/2″	304 Stainless Steel
Coastal Or High Corrosion Area	#14 Stainless Hex Washer With EPDM	316 Stainless Steel

Frequently Asked Questions

Are stainless screws required for all metal roofs?

Not always; many installations use coated carbon steel screws when panels and environment allow. Stainless is required in high-corrosion environments or per manufacturer warranty requirements.

Can the same screw be used for wood and metal substrates?

It is better to choose thread type for the substrate: coarse threads for wood and fine threads for metal for optimal holding power. Using the wrong thread reduces pull-out strength and holding capacity.

How long should screws penetrate the substrate?

Screws should penetrate structural substrate at least 3/8″ to 1/2″ for metal-to-metal and a minimum engagement depth recommended by the panel manufacturer for metal-to-wood. Insufficient embedment compromises strength under wind loads.

References And Manufacturer Guidance

Always consult the metal panel manufacturer’s fastener recommendations and local building codes: they provide specific fastener types, spacing, and torque settings. Following manufacturer installation guides preserves warranty and ensures optimal performance.