Metal Roofing Screws

Metal roofing screws might seem small and unimportant, but they can make or break your entire roofing system. These fasteners cost less than 1% of the total installation but can cause 100% of a roof’s failure if you choose or install them incorrectly.

Metal roofs usually last 40-70 years, but they’re not indestructible. Your fasteners’ performance relies on proper installation. Driving screws too deep damages the rubber washer and lets water seep in. Users of through-fastened metal roofing systems should pick quality options like fully encapsulated heads that come with lifetime warranties against red rust to ensure maximum protection.

This complete guide covers everything about screws for metal roof installations. You’ll learn about metal to wood roofing screws and sheet metal roofing screws, and become skilled at metal roof screw patterns. The guide gets into proper screw placement on metal roofing, required screws per sheet, and differences between metal to metal roofing screws and self-tapping ones. By the end, you’ll see how these small but vital metal roofing fasteners help create a durable, weather-tight installation.

Understanding the Role of Screws in Metal Roofing

Fasteners are the foundations of any metal roofing system. They make up less than 2% of construction costs—usually under 1% of total project expenses—but these small components can make or break a project’s success. They determine if a metal roof will last for decades or need repairs soon after installation.

Why fasteners are critical to roof longevity

A metal roof’s lifespan depends on its fastener quality. The Metal Construction Association’s studies show that a well-installed Galvalume roof can last over 60 years. However, this impressive longevity depends entirely on using appropriate long-life fasteners. Poor quality fasteners can cut a metal roof’s life by 40 years or more.

Quality fasteners come with warranties that guarantee their stability and performance, giving property owners peace of mind. These components help roof installations last much longer compared to lower-grade options.

Fastener quality and metal panel performance go hand in hand. The most advanced metal roofing sheets only reach their expected lifespan when screws and accessories perform just as well. Using high-tech metal roofing sheets with low-quality screws wastes the investment in premium panels.

You need regular inspections and maintenance to get the most from your fasteners:

• Check every two years in coastal, humid, or industrial areas
• Inspect every five years in rural, cleaner areas
• Replace corroded fasteners right away to stop damage from reaching roof panels

How screws affect weather resistance and structure

Metal roofing fasteners play a vital role in keeping structures intact. Loose fasteners can let metal roofing panels slip or slide and cause major structural damage. Quality fasteners also keep wind and water out, which saves money on repairs.

Metal roofs expand and contract as temperatures change, which can loosen screws. Loose screws let panels move or lift up, creating gaps where water can damage the roof deck below. The screw pattern helps the roof handle these forces.

Well-placed screws offer several benefits:

• They stop panels from getting too much stress and spread the load evenly
• They seal tightly to stop water leaks
• They lower the risk of panel warping or loosening

Screw location—on ribs or flat surfaces—changes how well they work and how long they last. Rib-mounted screws stay drier and handle heat movement better. Flat-mounted screws hold panels more securely and spread pressure more evenly, which helps panels keep their shape.

The fastener material must match the roof material to prevent galvanic corrosion. Areas near the coast, where salt spray turns into a haze, need top-grade corrosion-resistant fasteners.

High-quality fasteners deliver better strength and fight corrosion more effectively, so they handle weather stress better over time. Though they cost more upfront, they save money by lasting longer and needing fewer replacements throughout the roof’s life.

Key Factors to Consider When Choosing Screws

The right metal roofing screws can make or break your project. Your choice will affect how easy it is to install and how well your roof performs over time. A good understanding of these specifications helps you avoid mistakes that can get pricey and gives your roof the longest possible life.

Panel system type: exposed vs concealed

Metal roofing uses either exposed or concealed fastener systems. Each system needs specific types of screws because they work differently.

Exposed fastener systems need screws that go straight through metal panels into the structure below. These systems cost less and installation is straightforward. You’ll need fasteners with rubber sealing washers to keep water out and stop leaks.

Concealed fastener systems, like standing seam panels, keep fasteners hidden. These systems work best with low-profile head screws that don’t touch the panel’s underside. Snap-lock standing seam needs pancake head fasteners, while nail-strip standing seam works better with extra low-profile fasteners.

Screw material and coating options

Your screws’ material must match your roofing material. This prevents galvanic corrosion that happens when different metals touch each other around moisture.

Each roofing material needs specific fasteners:

• Aluminum roofing: Use type 304 stainless steel screws with matching paint color
• Copper roofing: Choose type 410 stainless steel screws with copper plating
• Corten roofing: Select stainless steel screws with dark brown painted heads
• Standard metal roofing: Use zinc-plated (galvanized) screws

Carbon steel and stainless steel are common materials, and galvanized coatings lead the market. Quality coatings protect against corrosion, especially near the coast or in industrial areas where salt and pollutants speed up wear.

Screw length and drill point types

The right screw length makes a big difference. Short screws won’t grip well enough, while long ones might damage what’s underneath. A good rule is to have at least one inch of screw go into the material you’re fastening to.

Different panels need different lengths:

• Standing seam: 1″ pancake heads for fastening clips
• ½” Corrugated panels: Minimum 1.5″ screws when fastening to the high point
• ⅞” Corrugated panels: Minimum 2″ screws when fastening to the high point
• R-Panel/7.2 Panel: 1″ screws when fastening to the low point

Pick your drill points based on what you’re drilling into:

• Self-drilling screws work without pre-drilling in most cases
• Self-tapping screws need a pilot hole and work great over existing roofs
• Self-piercing screws cut through thicker materials better

Color matching for aesthetic finish

Visible fasteners should match your roof’s color to look professional. Manufacturers make screws in colors that match standard metal roofing panels. Colored heads merge naturally with your roofing material and look great.

You’ll find plenty of color choices, with some makers offering more than 20 standard colors to match common metal roofing shades. This detail matters a lot for how exposed fastener systems look.

Thread count and head style

A screw’s thread count (threads per inch or TPI) shows how well it grips. For instance, a #12-24 screw has a #12 diameter and 24 threads per inch.

Common thread patterns include:

• #9 & #10: Best for metal-to-wood applications
• #12: Perfect for metal-to-metal applications
• #14: Great for areas with heavy snow loads

Head styles change based on what you need:

• Hex washer heads give you a strong bearing surface and are most popular
• Pancake heads work great in concealed fastener systems
• Truss heads offer large, low-profile designs for specific uses
• Flat heads sit flush with surfaces for a clean look

These details help you pick metal roofing screws that work best for your project’s specific needs.

Types of Metal Roofing Screws Explained

Metal roofing projects need the right fasteners, and today’s market offers several distinct types. Each type works best for specific uses and brings unique advantages to different installations.

Metal to wood roofing screws

Metal to wood roofing screws attach metal panels straight to wooden surfaces using coarse threads that grip exceptionally well. You’ll find these fasteners in #9 and #10 diameters with sharp points that go through both metal and wood without pre-drilling. Their EPDM (rubber) washers create waterproof seals even at angles. These screws use special transition threads that switch from fine to coarse, which creates a stronger hold in different wood materials.

Some specialty options stand out. ZXL Woodbinders use ZAMAC 5 Zinc-Aluminum alloy heads to protect against red rust for life. Eclipse Woodbinders feature low-profile round heads and T25 6-lobe recess, perfect for sidewall projects where protruding fasteners might hurt animals.

Metal to metal roofing screws

These fasteners connect metal roofing sheets to steel purlins or frames. The screws have finer threads and self-drilling tips, so you won’t need to pre-drill. They come in #12 standard size and #14 oversized “rescue screws” to replace loose fasteners.

Different models drill through various steel thicknesses. Standard versions work with steel up to .210″ thick, while heavy-duty ones can handle steel up to .500″ thick. Many have cupped heads that lock in the EPDM washer, keeping seals waterproof during temperature changes.

Trim and lap screws

Stitch screws, as they’re commonly known, join overlapping metal panels, flashing, gutters, and trim. These screws run shorter (¾” to ⅞”) than regular roofing screws and use tapered threads that grip firmly in corrugated panel ribs.

You need these screws to seal panel overlaps properly and stop water from getting in at connection points. Many brands make lap screws in colors that match their standard fasteners for a clean look.

Self-drilling (Tek) screws

Teks® fasteners changed metal roofing installation by drilling, tapping, and fastening all at once. These screws save time since they don’t need pre-drilling. Their drill points come in different sizes – #1 works for light gauge steel while #5 handles structural steel up to 12.5mm thick.

Heavy gauge steel screws

Heavy gauge screws tackle structural jobs with larger diameters (#12-24, #14, and #17) and special drill points that work with steel up to .500″ thick. These screws use a specific thread-to-point ratio to maximize pull-out strength in tough jobs like attaching metal deck to structural steel or bar joists. They’re built to last with advanced protection against corrosion, using either ZAMAC alloy heads or special coatings that survive 1000-hour salt spray tests.

Installation Best Practices for Metal Roofing Screws

Metal roofing screws need precise installation. Your roof can develop leaks, structural problems, and fail prematurely even if you select perfect fasteners but install them incorrectly.

Correct screw placement on metal roof

The panel profile determines where to place screws. You should install fasteners on the crown/crest corrugation instead of valleys for corrugated metal roofing. This prevents water and debris from collecting in low spots. Screws placed on the ribs stay away from standing water and create a better weather seal.

R-Panel, 7.2 Panel, and Western Rib profiles need five panel screws and one lap screw per screw line in the panel low. The manufacturer’s recommendations should guide your installation since incorrect placement voids warranties.

Screw pattern for metal roofing

Wind conditions determine screw patterns. Mild wind areas need fasteners on alternate ribs at end/external purlins and every second rib at middle/internal purlins. High wind zones require screws on each rib of external purlins, and you might need to cut spacing in half to add strength.

Most installers place screw lines 24″ on center, though spacing ranges from 18″ to 36″ O.C. based on structural needs. The first step is to create consistent screw lines across panel width that distribute load evenly and look good.

How many screws per sheet of metal roofing

A standard 100-square-foot sheet needs about 80 screws. You can calculate total screw requirements by multiplying roof square footage by 80%. You also need extra fasteners for trim and sidelap:

• 1-2 screws per lineal foot of trim/flashing
• 2-4 screws per lineal foot of panel sidelap

Avoiding over-tightening and washer damage

Over-tightening ranks among the worst installation mistakes. When properly installed, the rubber washer should spread to the edge of the metal cap but not beyond it. A loose screw allows the washer to spin after installation.

A screw gun with adjustable clutch and depth sensing works best—not an impact driver that often causes screw failures. The manufacturer’s specs usually call for 30-40 inch pounds of torque.

Choosing the right screw length

Your screws should penetrate at least one inch into the substrate material. Different panels need specific screw lengths:

• Standing seam: 1″ pancake heads for clip fastening
• ½” Corrugated: Minimum 1.5″ screws when fastening to the high point
• ⅞” Corrugated: Minimum 2″ screws when fastening to the high point
• R-Panel/7.2 Panel: 1″ screws when fastening to the low point

Longer screws create more torsional strain while driving, which sometimes causes them to break during installation.

Preventing Common Issues and Ensuring Durability

Metal roofing systems last longer when you prevent problems early. Yes, it is possible for premium systems to fail ahead of time without proper maintenance and careful attention.

Avoiding galvanic corrosion

Galvanic corrosion happens when different metals touch each other with moisture present. This electrochemical process slowly eats away the less noble metal where connections meet. You can prevent this destructive reaction by:

• Choosing metal roofing screws that match your panel composition
• Adding non-conductive coatings like bituminous primers between different metals
• Keeping copper fasteners away from aluminum or zinc-coated panels
• Stopping runoff from nobler metals onto less noble ones

Even tiny amounts of copper from treated wood or graphite from pencil marks can start corrosion on aluminum panels.

Replacing old or failed screws

Select fasteners one size wider than the original when you replace metal roofing screws. This creates new threads in existing holes. Stainless steel bimetal varieties work best as replacement screws in previously rusted areas.

Inspecting for loose or backed-out fasteners

Temperature changes make roof panels expand and contract, which loosens fasteners over time. You should check visually each year for protruding screws or damaged washers. The screw needs immediate tightening if you can turn its washer with your fingers.

Using high-quality sealing washers

EPDM rubber washers backed with stainless steel deliver the best waterproofing results. A correctly installed washer should reach the metal cap’s edge without bulging past it. Three common installation mistakes damage these essential components: excessive compression from over-driving, incomplete seating from under-driving, and angled installation.

Summing all up

Metal roofing screws make up just a small part of your roofing investment. But their effect on system performance is huge. This piece shows how these tiny components determine if your metal roof will last its promised 40-70 years or fail early.

The right fasteners for your panel system, substrate material, and environment will pay off in the long run. Quality screws with proper coatings and compatible materials cut down maintenance costs and work reliably for decades. On top of that, proper installation techniques – especially when you have to consider screw placement, pattern, quantity, and torque – stop the most common roof failures.

Premium fasteners cost just pennies more per screw than simple ones. This small investment cuts the risk of pricey repairs, structural damage, and early replacement by a lot. Smart property owners see quality fasteners as vital protection against future problems, not just an extra expense.

Note that even the best-made screws will fail if they’re not installed right. Using the right tools, avoiding over-tightening, and following manufacturer’s guidelines are just as important as picking the right fastener type.

Regular checks are your best defense against problems. Fasteners tend to loosen as temperatures change and materials expand and contract. Finding and fixing these issues early stops small problems from turning into major structural damage.

Metal roofing systems are tough, weather-resistant, and long-lasting – but only when every part, especially fasteners, meets quality standards. These small but mighty components make up less than 1% of total costs. Yet they ended up deciding if your roof investment gives you decades of protection or gets pricey to replace too soon.

Here are some FAQs about the metal roofing screws:

What kind of screws to use for metal roofing?

For metal roofing, you should use specialized metal roofing screws that are designed to withstand outdoor conditions. These sheet metal roofing screws typically feature neoprene washers to create watertight seals and sharp points for easy penetration. Metal to wood roofing screws are specifically designed when attaching metal panels directly to wooden substrates.

What is the correct way to screw down metal roofing?

The correct way to install metal roofing screws involves placing them in the flat portion of the metal panels, not the ribs. You should drive sheet metal roofing screws straight and perpendicular to the surface to ensure proper sealing. When determining how many screws per sheet of metal roofing, follow manufacturer guidelines which typically specify spacing every 12-24 inches along supports.

What are roofing screws called?

Roofing screws for metal installations are commonly called metal roofing screws or sheet metal roofing screws. These fasteners are specifically designed with washers and special threads for roofing applications. Metal to wood roofing screws refer to the variety used when attaching metal panels directly to wooden decking or purlins.

Do metal roofs leak at the screws?

Properly installed metal roofing screws with intact washers should not leak, as the neoprene gaskets create watertight seals. The key is using the correct how many screws for metal roofing spacing and ensuring screws aren’t over-tightened. Metal to wood roofing screws with damaged or missing washers are the most common source of potential leaks in metal roof systems.

How tight should screws be on a metal roof?

Metal roofing screws should be tightened just enough to compress the neoprene washer slightly without over-compressing it. Sheet metal roofing screws that are too tight can damage the washer and compromise the waterproof seal. When installing how many screws per sheet of metal roofing, use a drill with adjustable torque to achieve consistent, proper tightness across all fasteners.

Can I screw metal roofing directly on plywood?

Yes, you can attach metal roofing directly to plywood using special metal to wood roofing screws designed for this purpose. The key is using the correct how many screws for metal roofing spacing – typically every 12-18 inches along supports. Sheet metal roofing screws with sharp points and coarse threads work best for direct plywood attachment without pre-drilling.