6 Best Rust-Proof Washers For Attaching Metal Roofing To Sheds

A leaking shed roof can ruin a season’s worth of expensive animal feed or rust out high-end garden tools in weeks. While the metal panels get all the attention, the small washers at every fastener point are the true gatekeepers of a dry interior. Selecting the right rust-proof washer ensures that your storage space remains a functional asset rather than a moisture-trap liability.

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Bolt Dropper Stainless EPDM Washers: Best Overall

These washers combine a high-quality 304 stainless steel backing with a thick EPDM rubber seal. The stainless steel provides exceptional resistance to the elements, preventing the unsightly rust streaks that often plague agricultural buildings. Because 304 stainless is non-reactive with most metal roofing panels, you avoid the galvanic corrosion that occurs when mismatched metals meet.

The EPDM rubber is specifically formulated to withstand the intense UV radiation found on top of a shed. Unlike standard rubber, EPDM won’t become brittle or crack after a single summer of direct sunlight. This ensures the seal remains flexible, moving with the metal as it expands and contracts through the changing seasons.

For a hobby farmer looking for a “one and done” solution, these are the gold standard. They offer the best balance of longevity, ease of installation, and chemical resistance. Buy these if you want the highest level of protection and never want to climb back on that roof to fix a leak again.

Hillman Neoprene Bonded Washers: Most Versatile

Hillman offers a reliable bonded washer that works across a variety of fastener types, making them a staple in many farm workshops. The neoprene seal is slightly softer than EPDM, which allows it to conform easily to minor imperfections in the metal sheeting. This makes them particularly useful when retrofitting older sheds where the panels might have slight dings or waves.

The galvanized steel backing provides a strong physical foundation that resists bending under pressure. While galvanized steel isn’t quite as corrosion-resistant as stainless, it is perfectly suited for most inland environments. These washers are frequently used for both roofing and side-wall applications on outbuildings.

These are the workhorse washers of the small-scale farm. They perform consistently across different climates and project types without requiring a massive investment. Reach for these when you need a dependable, multi-purpose washer that handles both new construction and quick repairs with ease.

Teks Galvanized Steel Sealing Washers: Best Value

Teks provides a cost-effective solution for those covering large square footages on a tight budget. These washers feature a heavy-duty zinc coating that protects the steel from moisture and oxidation. While they may require more frequent inspection than stainless options, they offer significant savings when building a large hay barn or machine shed.

The sealing element is designed to compress evenly, creating a watertight barrier around the screw shank. This design prevents water from “wicking” down the threads and rotting the wooden purlins or trusses underneath. In many agricultural settings, these provide all the protection necessary for a fraction of the cost.

Value doesn’t have to mean compromising on quality for standard farm applications. These washers meet the structural requirements for most metal roofing systems while keeping project costs manageable. These are the clear choice for the budget-conscious builder tackling a large outbuilding in a moderate climate.

Prime-Line Stainless Neoprene Washers: Extra Durable

When a structure is located in a harsh environment, such as a coastal area or near a compost site, standard hardware often fails. Prime-Line addresses this with a thick stainless steel shell that resists both physical deformation and chemical attack. The extra thickness in the metal backing prevents the washer from “cupping” or turning inside out if a gust of wind catches the roof.

The neoprene layer is bonded securely to the metal, ensuring it won’t peel away during the friction of installation. This bond is crucial for maintaining a seal over decades rather than years. The durability of these washers makes them a favorite for structures housing livestock, where humidity and ammonia levels can be higher than average.

These are built to withstand abuse that would destroy lesser fasteners. They provide peace of mind in high-wind zones where the roof is under constant mechanical stress. Invest in these for structures exposed to harsh chemicals or extreme weather where standard hardware simply won’t survive.

Simpson Strong-Tie EPDM Washers: Heavy Duty Pick

Simpson Strong-Tie is synonymous with structural integrity, and their roofing washers are no exception. These are engineered to handle higher torque loads, which is essential when securing heavy-gauge metal panels. The EPDM seal is wider than many competitors, providing a larger footprint to distribute the clamping force.

This wider footprint is a massive advantage when working with thin-gauge metal that might otherwise tear or “dimple” under the pressure of a screw. By spreading the load, these washers help maintain the structural profile of the roofing ribs. This ensures that water sheds off the roof as designed rather than pooling around the fastener.

For the farmer building a permanent structure intended to last a lifetime, these offer unmatched security. They bridge the gap between simple hardware and structural engineering components. Choose these for structural barns or equipment sheds where fastener failure or metal tearing is simply not an option.

SupaDrive Silicone Sealing Washers: Best for Heat

In regions with extreme summer temperatures, standard rubber and EPDM can eventually “bake” and lose their elasticity. SupaDrive utilizes silicone for the sealing element, which has a much higher thermal threshold than traditional materials. This prevents the washer from melting or sticking to the roof panel during the hottest parts of the day.

Silicone also remains remarkably flexible in freezing temperatures, which prevents the seal from snapping during a winter thaw-freeze cycle. This stability across temperature extremes makes these ideal for mountainous regions or desert climates. The material is also naturally hydrophobic, meaning it actively repels water away from the hole.

If your shed sits in a location with no shade and high sun exposure, these are the specialized tool you need. They outperform organic rubbers in the specific area of thermal degradation. Select these if your shed sits in direct, unrelenting sun or experiences massive seasonal temperature swings.

How to Choose the Right Rust-Proof Washer Material

Choosing the right material begins with understanding your local environment and the metal of your roofing. If you are using aluminum roofing, you must use stainless steel washers to prevent a chemical reaction between the metals. For standard galvanized steel roofing, you can use either galvanized or stainless washers, though stainless will always offer a longer lifespan.

The sealing material is just as important as the metal backing. EPDM is the industry standard for most roofing applications because it handles UV rays and ozone better than standard rubber. Neoprene is an excellent alternative for general use, especially if the washer might come into contact with oils or fuels near a tractor shed.

• 304 Stainless Steel: Best for general corrosion resistance and longevity.
• 316 Stainless Steel: Necessary for coastal environments with salt spray.
• Galvanized Steel: Practical and cost-effective for dry, inland climates.
• EPDM Rubber: The best all-around choice for UV and weather resistance.

Consider the longevity of the roof panels themselves when picking your washers. If you have invested in high-end, 40-year painted panels, it makes little sense to use 10-year galvanized washers. Match the lifespan of your fasteners to the lifespan of your roofing material to avoid premature maintenance cycles.

Sizing Your Washers Correctly to Prevent Shed Leaks

A washer that is too small will not cover the hole drilled for the fastener, leading to immediate leaks. Conversely, a washer that is too large can become a “catch-all” for debris, holding moisture against the screw head. Most shed roofing uses #10 or #12 screws, which typically require a 1/2-inch or 9/16-inch outside diameter washer.

Check the diameter of the screw head before purchasing your washers. The metal backing of the washer should be slightly larger than the head of the screw to ensure the pressure is distributed onto the rubber seal. If the screw head is larger than the metal backing, it will simply crush the rubber without providing a proper seal.

Always account for the “squish factor” when sizing. When a washer is tightened, the rubber or EPDM will expand outward. You want a size that, when fully compressed, covers the entry point completely without bulging out so far that the rubber loses its structural bond with the metal backing.

How to Avoid Overtightening Metal Roofing Screws

Overtightening is the most common mistake made during shed construction. When a screw is driven too deep, the washer “cups” upward, and the rubber seal is forced out from the sides. This creates a concave area around the screw that actually traps water, leading to rust and leaks directly over the hole.

The goal is to tighten the fastener until the rubber seal is compressed just to the edge of the metal backing. You should see a slight, uniform bulge of rubber around the perimeter, but the metal backing should remain flat. If the rubber starts to look like a pancake or begins to split, you have gone too far.

Using a drill with an adjustable clutch is the best way to ensure consistency across the entire roof. Start with a lower torque setting and increase it until the washers are seating correctly. This prevents the “hit or miss” results that come from manual tightening or high-impact drivers that can easily strip the wood underneath.

When to Inspect and Replace Aged Roofing Washers

Roofing washers are the “tires” of your shed; they are the only part of the roof designed to wear out over time. It is wise to perform a visual inspection every two years, or after any major hail storm. Look for visible cracks in the rubber, washers that have “spun” loose, or any signs of rust streaks originating from the screw head.

If you can see light through the fastener holes from inside the shed, the washers have likely failed. Another sign of failure is “chalking,” where the EPDM or neoprene turns into a white powder when touched. This indicates the UV inhibitors have been exhausted and the seal is no longer watertight.

Replacing a single washer is a simple task that involves backing out the screw, sliding on a new washer, and re-seating it. However, if more than 10% of the washers on a roof show signs of cracking, it is usually more efficient to replace them all at once. This proactive approach prevents the structural rot that occurs when small leaks go unnoticed for several seasons.

Taking the time to select and maintain the right washers is a hallmark of a well-managed farm. These small components protect your equipment, your livestock feed, and the structural integrity of your buildings. By matching the right material to your specific climate, you ensure that your shed remains a dry, productive space for decades to come.