10 Common Roofing Screw Mistakes That Can Ruin Your Project (And How to Avoid Them)

Roofing screws may seem like a small detail in the massive task of building or maintaining a roof, but they often determine whether your project lasts decades or fails within a few years. Time and again, builders, contractors, and even DIY homeowners make the same mistakes with roofing fasteners—sometimes without even realizing it. These mistakes can lead to leaks, rust stains, sheet cracks, or worse, roof failure during storms.

The truth is, a screw isn’t “just a screw.” Different materials, coatings, lengths, and installation methods all matter. For example, a screw that works fine on timber may completely fail when used on steel purlins. Similarly, a cheap washer may cause a hidden leak that damages insulation or ceilings over time.

In this guide, we’ll uncover the 10 most common roofing screw mistakes that could ruin your project—and show you how to avoid them. Whether you’re a contractor looking to deliver long-lasting quality or a homeowner who wants peace of mind, this article will give you the clarity you need to build with confidence.

Mistake 1 – Over-Tightening Screws

One of the most common mistakes in roofing projects is over-tightening screws. Many installers assume that the tighter the screw, the stronger the hold. In reality, it’s the opposite. When screws are over-driven into roofing sheets, two major issues occur:

Cracked Sheets – Fiber cement or polycarbonate sheets are particularly vulnerable. Extra pressure from over-tightening creates micro-cracks around the hole, which expand over time due to thermal movement. Eventually, the sheet can fail completely.
Damaged Washers – EPDM washers are designed to sit snugly under the screw head, creating a watertight seal. But when a screw is forced down too tightly, the washer flattens or tears, losing its sealing ability. This leads to hidden leaks that might only become visible months later.

The correct way to fasten roofing screws is to ensure they’re flush, not buried. The washer should be compressed just enough to create a seal but not distorted. Using a drill with adjustable torque settings is the best way to achieve consistency across hundreds of screws in a project.

✅ Pro Tip: Always stop driving once the washer starts to compress—don’t wait until it looks crushed.

Mistake 2 – Using the Wrong Screw Type for the Material

Not all screws are created equal — and using the wrong type for your roofing material is a recipe for disaster. Many contractors make the mistake of using generic wood screws or nails on metal, fiber cement, or polycarbonate sheets. While it might save money upfront, the long-term consequences are costly.

For example:

Metal Sheets require self-drilling metal screws with hardened points to pierce steel purlins cleanly. A wood screw will simply spin or snap.
Polycarbonate Sheets expand and contract under heat. Ordinary screws without wings don’t allow for this movement, causing cracks around the holes.
Fiber Cement Sheets need wafer head screws designed for brittle materials. Regular screws can crush the sheet edge and reduce load-bearing capacity.

When the wrong screw is used, sheets may loosen, crack, or corrode prematurely. Worse, the roof’s structural safety is compromised. The cost of re-installation and replacing damaged sheets far outweighs the small saving from using “cheap” or unsuitable fasteners.

✅ Pro Tip: Always match the screw type to both the sheet material and the frame type (steel, timber, or concrete). This ensures long-term performance and fewer call-backs.

Mistake 3 – Ignoring Corrosion Protection

One of the biggest mistakes in roofing projects is overlooking corrosion resistance when selecting screws. Fasteners are constantly exposed to rain, humidity, temperature changes, and sometimes even coastal salt spray. If the screws aren’t properly coated or made from durable materials, rust sets in quickly.

This rust doesn’t just look ugly — it weakens the screws’ grip, stains the roof sheets, and eventually leads to leaks or structural failures. For instance, using plain galvanized screws on coastal projects often results in reddish-brown streaks within a year. Once corrosion starts, replacing hundreds (or thousands) of screws is both costly and labor-intensive.

To avoid this, professionals rely on:

Ruspert-coated screws for general construction.
Multi-layer Rust Shield coatings for extended life in industrial or humid zones.
Stainless steel screws in highly corrosive environments like coastal or chemical plants.

✅ Pro Tip: Always check the AS3566-2002 corrosion class rating (Class 3 or Class 4) when purchasing roofing screws. This ensures your fasteners can withstand the environment they’re installed in.

By prioritizing corrosion protection, you’re not just preventing rust — you’re extending the lifespan of the entire roof system.

Mistake 4 – Under-Driving Screws

While over-tightening is a known issue, another common mistake is the opposite — under-driving screws. This happens when screws are not driven deep enough to properly compress the washer against the roofing sheet.

The consequences are serious:

Washers remain loose, leaving tiny gaps that allow water penetration.
Roof sheets may vibrate or lift during strong winds, leading to premature wear or even sheet displacement.
Loose screws create uneven pressure points, increasing the risk of cracks around holes.

Why it happens:

Using drills with insufficient torque or improper clutch settings.
Workers rushing installation and not checking flush alignment.
Incorrect bit sizes leading to reduced grip.

How to avoid it:

Always use a calibrated screw gun with proper torque settings.
Perform a quick visual check row by row — properly driven screws should sit flush, with the washer slightly compressed but not distorted.
For large projects, assign a supervisor to inspect fastening quality regularly.

✅ Pro Tip: Training workers to recognize the subtle difference between a “snug fit” and a “loose fit” can drastically reduce under-driving errors.

Mistake 5 – Using the Wrong Washer Type

Washers may seem like a small part of a roofing screw, but choosing the wrong type is one of the biggest mistakes contractors make. Many low-quality screws come with PVC or low-grade rubber washers that harden, crack, or shrink under sunlight and weather exposure.

When this happens:

Water seeps in through the screw hole, causing hidden leaks.
Washers lose flexibility, which leads to loose fastening over time.
Rust stains may appear around the screw holes, ruining the building’s appearance.

Common mistake: Using cheap black neoprene washers instead of high-quality EPDM washers. While both look similar, EPDM is engineered to withstand UV, heat, and rain without cracking.

How to avoid it:

Always check washer material when buying screws — ask for EPDM-certified washers like DEKS TrueBlue.
Ensure washer size matches the sheet type (e.g., 19mm for general roofing, 26mm for polycarbonate).
Never reuse old washers, even if they “look fine” — their sealing ability reduces with age.

✅ Pro Tip: A high-quality screw with a poor washer is just as bad as a cheap screw. Think of washers as the roof’s first defense against leaks.

Mistake 6 – Using Screws of the Wrong Length

Another common mistake in roofing projects is choosing screws that are too short or too long for the material and structure. At first glance, it might not seem critical, but screw length directly affects holding strength and long-term durability.

Too short screws: They fail to penetrate deep enough into the purlin or timber, causing weak fastening. In strong winds, sheets may lift or even fly off.
Too long screws: They may punch through the underside of the frame, wasting effort, reducing grip efficiency, and sometimes damaging structural elements.

Why this happens: Many contractors use a “one-size-fits-all” approach instead of matching screw length to sheet thickness + purlin depth.

How to avoid it:

For metal-to-steel, choose screws with the right drill capacity (e.g., up to 4.5mm, 8mm, or 12mm thick steel).
For metal-to-wood, ensure at least 25mm bite into timber.
Always consider the thickness of roofing sheets plus insulation or underlayment before selecting screw length.

✅ Pro Tip: Refer to manufacturer charts or installation guides to determine the correct screw size. At Roofix, each screw type is clearly marked with its recommended applications to avoid guesswork.

Mistake 7 – Mixing Metals (Bimetallic Corrosion Risk)

One of the less obvious—but most damaging—mistakes in roofing projects is using screws made from a different metal than the roof sheet. This creates a problem called bimetallic corrosion.

When two dissimilar metals (for example, galvanized screws with aluminum sheets) come into contact with water, they form a chemical reaction that accelerates rust. The result?

Screws corrode much faster than expected.
Ugly rust streaks stain the entire roof.
Over time, the weakened fasteners fail, leading to leaks or even sheet detachment.

Why this happens: Contractors sometimes assume “metal is metal,” but not all metals are compatible. In roofing, material choice matters as much as size and coating.

How to avoid it:

Always match screw coating/metal with the roofing sheet material.
Use multi-layer coated screws (like Roofix Rust Shield) that protect against galvanic reaction.
For coastal or industrial environments, upgrade to Class 3 or Class 4 corrosion-resistant screws.

✅ Pro Tip: Even a small batch of incompatible screws can compromise the entire project. Consistency across all fasteners is the key to long-term performance.

Mistake 8 – Using Too Few Screws or Incorrect Spacing

Trying to save money by reducing the number of screws—or spacing them too far apart—is one of the biggest mistakes in roofing projects. At first, everything may look fine, but when strong winds, heavy rains, or storms hit, the sheets can:

Start flapping or vibrating, causing leaks.
Lift completely, leading to dangerous situations.
Put extra stress on the screws that are installed, making them fail faster.

Why this happens: Many contractors assume the manufacturer’s recommended screw count is “overkill.” But in reality, these calculations are based on wind load, sheet size, and structure design. Cutting corners here can lead to expensive repairs later.

How to avoid it:

Follow the recommended screw spacing for your specific sheet and building type.
Use more screws around the roof edges and ridges, where wind pressure is highest.
Always consult technical guidelines or ask your supplier for spacing charts.

✅ Pro Tip: Think of screws as the seatbelts of your roof—using fewer than required is a gamble you don’t want to take.

Mistake 9 – Ignoring Washer Quality

Washers may look like a small part of the fastener, but they are the first line of defense against leaks. Many roofing failures start not with the screw, but with a cheap, low-quality washer that cracks, hardens, or shrinks under the sun. Once this happens, rainwater seeps around the screw hole, slowly damaging insulation, ceilings, and sometimes even electrical systems.

Why this happens:

Many low-cost fasteners come with inferior rubber washers.
Exposure to UV rays and temperature changes causes them to lose flexibility.
Contractors often overlook washer quality because they focus only on the screw material.

How to avoid it:

Always choose screws with high-grade EPDM washers (like DEKS TrueBlue). These stay flexible and watertight for decades.
Avoid using PVC or neoprene washers—they deteriorate much faster.
Check that the washer size matches the screw head for a proper seal.

✅ Pro Tip: A premium washer can be the difference between a leak-free roof and costly water damage. Don’t cut corners here.

Mistake 10 – Choosing the Wrong Screw Type for the Job

Not all screws are created equal, and using the wrong type is one of the biggest mistakes contractors make. A screw that works perfectly for timber may fail miserably on steel. Similarly, a screw designed for thin sheets might shear when used on heavy PEB structures.

Common wrong choices:

Using wood screws for metal-to-metal applications.
Using light-duty self-drilling screws on thick hot-rolled beams.
Using standard screws on polycarbonate sheets instead of wing-tip screws.
Using non-coated screws in coastal or humid environments.

Why it matters:
Each screw is engineered for a specific application—wrong type = weak hold, cracks, rust, or even full roof failure.

How to avoid it:

Match screw type to material: self-drilling for steel, wood screws for timber, wing-tip for polycarbonate.
Consider coating (Rust Shield, Ruspert, Zinc) based on your environment.
Follow manufacturer’s recommendations for sheet thickness and load requirements.

✅ Pro Tip: Always think of screws as part of the roofing system—not just hardware. Choosing correctly ensures performance, durability, and safety.

Conclusion – Build Stronger Roofs, Avoid Costly Mistakes

Roofing projects succeed or fail not just because of the sheets or frames you choose, but because of the tiny screws that hold everything together. As we’ve seen, mistakes like over-tightening, under-driving, skipping washers, or choosing the wrong screw type can lead to leaks, cracks, rust, and even roof failure.

By paying attention to the details of fastening—from selecting the right screw type and coating, to proper spacing, installation technique, and quality washers—you ensure that your roof performs the way it should: strong, leak-free, and built to last.

At Roofix, we’ve seen these mistakes play out on real projects, and that’s why our screws are engineered with precision, durability, and compliance with international standards. Whether you’re working on a residential home, industrial shed, or PEB structure, choosing Roofix fasteners means avoiding costly errors and ensuring peace of mind.

👉 Don’t let small mistakes ruin big projects—choose the right screws with Roofix.

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