Metal Roof Leaks Around Screws – How To Identify And Fix Fastener
Metal roof leaks at the fasteners are usually caused by over-driven screws, degraded EPDM washers, or thermal expansion that widens the screw hole over time.
To fix these leaks, replace the failing fastener with an “oversized” metal roofing screw and ensure the new washer is compressed just enough to form a watertight seal without bulging.
Finding a puddle in your workshop or garage after a heavy rain is a frustrating experience for any DIYer. You spent time and money building a solid structure, but now moisture is threatening your tools and lumber. Dealing with metal roof leaks around screws can feel like a never-ending battle against the elements if you don’t know the root cause.
I promise that by the end of this guide, you will have the confidence to identify exactly why your roof is weeping and how to stop it for good. We are going to cover the mechanics of fastener failure, the specific tools you need for a permanent fix, and the pro-level techniques that keep high-end builds dry.
We will walk through a complete inspection process, explain the difference between various washer materials, and execute a step-by-step repair. Whether you are maintaining a small garden shed or a large pole barn, these strategies will protect your investment and keep your workspace bone-dry.
Common Causes of Metal Roof Leaks Around Screws
Metal roofs are incredibly durable, but they are also dynamic structures that move constantly. The primary reason we see metal roof leaks around screws is the natural cycle of expansion and contraction. As the sun beats down, the metal panels heat up and expand, then they cool and shrink at night.
This movement puts immense stress on the fasteners that hold the panels to the wood purlins or metal framing. Over several seasons, this “sawing” action can slightly enlarge the hole in the metal panel. Once the hole is larger than the gasket, water finds a direct path into your building.
Another common culprit is improper installation torque. If a screw is driven too tightly, the rubber washer will mushroom or crack, losing its ability to seal. Conversely, an under-driven screw leaves a gap where water can migrate under the head via capillary action.
The Role of the EPDM Washer
Most modern roofing screws utilize an EPDM (Ethylene Propylene Diene Monomer) washer. Unlike old-school neoprene, EPDM is designed to withstand intense UV exposure and extreme temperature swings without becoming brittle.
When these washers reach the end of their lifespan—typically 10 to 15 years—they begin to shrink and pull away from the metal surface. Once the seal is broken, even a light mist can lead to a drip. Identifying a degraded washer is the first step in your repair journey.
Impact of Backed-Out Screws
Sometimes, the wood purlins underneath the metal panels will shrink as they dry out over the years. This shrinkage can actually “spit” the screw back out just a fraction of an inch. Even a 1/16th-inch gap is enough to allow significant water intrusion during a wind-driven rainstorm.
Identifying Metal Roof Leaks Around Screws
Before you climb up on the roof, you need to be sure where the water is coming from. Water is sneaky; it often enters at one point and travels down a purlin or the underside of a rib before it finally drips. This can make the leak appear to be in a different spot than the actual fastener failure.
Start your investigation inside the building during a rainstorm if possible. Use a high-lumen flashlight to track the path of the water. Look for drip patterns or rust stains around the points where the screws penetrate the roof deck or purlins.
If the roof is dry, look for “tracking” marks. These are dust or mineral deposits left behind by evaporated water. Once you have a general area identified, it is time to move to the exterior for a closer look at the fasteners.
Visual Inspection from the Roof
Safety is your first priority when working on a metal roof. Always use a fall protection harness and wear soft-soled shoes with excellent grip. Avoid working on a wet roof, as metal becomes incredibly slick with even a small amount of moisture.
Walk the rows of screws in the suspect area and look for any washers that appear “squished” or off-center. If you see a screw head that isn’t sitting flush against the metal, you have likely found your leak. Pay close attention to the screws located in the valleys of the metal profile, as these handle the most water runoff.
The “Wiggle” Test
Sometimes a screw looks fine but has lost its “bite” in the wood below. Using a nut driver, gently check the tension on the screw. If it spins freely or feels loose, the wood substrate may be stripped or rotted. This requires a different fix than simply tightening the fastener.
Essential Tools and Materials for the Repair
To address metal roof leaks around screws, you need more than just a standard screwdriver. Using the right materials ensures that you won’t be back up on the roof in six months doing the same job again.
- Impact Driver or Drill: A cordless impact driver is best for removing and driving roofing screws with precision.
- Magnetic Nut Driver: Most roofing screws use a 1/4-inch or 5/16th-inch hex head. A magnetic tip prevents you from dropping screws on the ground.
- Oversized Roofing Screws: These are often called “replacement screws” or “XL fasteners.” They have a slightly larger diameter thread to grip into stripped wood holes.
- Polyurethane Sealant: Avoid standard 100% silicone. Use a high-quality polyurethane sealant specifically rated for metal roofing.
- Wire Brush and Rags: For cleaning the area around the leak to ensure proper sealant adhesion.
Using oversized fasteners is the secret weapon for DIYers. If a standard #9 screw has stripped the wood, stepping up to a #12 or #14 replacement screw will provide the mechanical tension needed to compress the new washer effectively.
Step-by-Step Guide to Fixing Metal Roof Leaks Around Screws
Now that you have your tools and have identified the problem areas, it is time to perform the repair. This process is straightforward, but attention to detail is what separates a temporary patch from a permanent solution.
Step 1: Removing the Old Fastener
Back out the leaking screw slowly. Inspect the screw as it comes out. If the threads are covered in wood pulp or moisture, it indicates that the purlin underneath might be damp. If the screw is rusted through, the leak has likely been happening for a long time.
Step 2: Cleaning the Surface
You cannot get a good seal on a dirty roof. Use a small wire brush or a stiff nylon brush to remove any rust, lichen, or old sealant from around the hole. Wipe the area with a clean rag and a bit of isopropyl alcohol to remove any oily residue.
Step 3: Preparing the Hole
If the hole in the metal panel has become significantly elongated, you may want to apply a small bead of polyurethane sealant directly into the hole before inserting the new screw. This provides a “secondary” gasket inside the wood purlin itself.
Step 4: Installing the New “Oversized” Screw
Place the new oversized screw into the hole. Drive it in steadily until the EPDM washer touches the metal. Here is the critical part: Stop driving once the washer is compressed to the edge of the screw head. You want the washer to be firm, but not bulging out past the metal cap.
Step 5: Final Inspection
Check the seal by trying to rotate the washer with your fingers. It should be tight enough that it doesn’t move. If you are dealing with a particularly stubborn leak, you can apply a small “cap” of sealant over the head of the screw, though this is usually unnecessary if the washer is seated correctly.
Alternative Methods: When Screws Aren’t the Only Issue
Sometimes, you might find that metal roof leaks around screws are actually symptoms of a larger problem, like poor flashing or clogged gutters. If you replace the screws and the leak persists, look at the overlapping seams of the metal panels.
Capillary action can pull water “uphill” between two overlapping sheets of metal if there isn’t enough pitch or if the butyl tape between the seams has failed. In these cases, you may need to add stitch screws to the ribs to pull the panels tighter together.
Using Repair Tapes
For emergency repairs during a storm, specialized butyl-backed flashing tapes can be a lifesaver. These tapes bond incredibly well to metal and can cover a leaking screw head instantly. However, these should be considered temporary fixes until you can install a mechanical fastener.
Preventing Future Leaks Through Maintenance
The best way to handle metal roof leaks around screws is to prevent them from happening in the first place. A quick annual inspection can save you thousands of dollars in structural repairs down the road.
Every spring, take a walk around your roof (or use binoculars from the ground). Look for “shiners”—screws that have backed out and are reflecting light differently than the others. Catching a backed-out screw before the next big rainstorm is the hallmark of a proactive homeowner.
Keep your roof clear of debris. Leaves and pine needles trap moisture against the screw heads, accelerating the corrosion of the washers. A clean roof dries faster and lasts longer.
Frequently Asked Questions About Metal Roof Leaks Around Screws
Why do metal roof leaks around screws happen even on new roofs?
On new roofs, leaks are almost always due to installation errors. This includes over-driving screws (cracking the washer), under-driving screws (leaving a gap), or driving screws at an angle so the washer doesn’t sit flush against the metal panel.
Can I just use caulk to stop metal roof leaks around screws?
While you can use caulk as a temporary fix, it is not a permanent solution. The expansion and contraction of the metal will eventually break the bond of the caulk. Replacing the fastener with a new EPDM washer is the only way to ensure a long-term seal.
What is the difference between Neoprene and EPDM washers?
Neoprene was the standard for years, but it tends to dry out and crack when exposed to UV rays. EPDM is a synthetic rubber that remains flexible and UV-resistant for much longer, making it the superior choice for roofing applications.
How do I know if my roof purlins are rotted?
If you install a new, oversized screw and it still won’t “bite” or tighten down, the wood underneath is likely rotted. In this case, you may need to install a small block of wood (sistering) from the underside or shift the screw location slightly and patch the old hole.
Protecting Your Workshop for the Long Haul
Mastering the repair of metal roof leaks around screws is an essential skill for any DIYer who manages their own property. It transforms a stressful situation into a simple afternoon project, ensuring that your tools, projects, and substructure remain protected from water damage.
Remember that a metal roof is a living system that breathes and moves with the temperature. By using high-quality EPDM washers, choosing the right oversized fasteners, and respecting the proper torque settings, you create a seal that can withstand the harshest weather.
Don’t wait for the next major storm to test your roof’s integrity. Grab your ladder, perform a quick inspection, and swap out those aging fasteners today. Your workshop—and everything inside it—will thank you for the effort.
