Types of Washers and When to Use Them
Washers may be small, but they do a big job. They help spread load, protect surfaces, reduce loosening, and improve the performance of bolts, screws, and nuts. Whether you’re building a deck, anchoring steel, assembling equipment, or handling general repairs, choosing the right washer helps create a cleaner, stronger connection.
What Is a Washer?
A washer is a thin plate, usually round, with a hole in the center, used with a fastener. It sits between the fastener head or nut and the material being fastened. Washers help distribute pressure, reduce surface damage, and improve hold.
Common Types of Washers
Flat Washers
Flat washers are the most common type. They spread the load of a bolt, screw, or nut across a larger surface area. This helps prevent the fastener from digging into wood, metal, plastic, or other materials.
Best for: General fastening, wood connections, metal assemblies, and surface protection.
Fender Washers
Fender washers have a larger outside diameter than standard flat washers. That extra width spreads force over a wider area, making them useful when fastening thin sheet metal, oversized holes, or softer materials.
Best for: Sheet metal, automotive work, repairs, and applications where extra bearing surface is needed.
Split Lock Washers
Lock washers are designed to help resist loosening caused by vibration or movement. Split lock washers are one of the most recognizable styles, with a cut and slight twist that adds tension under the fastener.
Best for: Machinery, equipment, metal assemblies, and applications exposed to vibration.
Structural Washers
Structural washers are heavy-duty washers used with structural bolts in steel construction. They are thicker and stronger than standard washers, helping support high-load connections.
Best for: Steel framing, structural bolting, and heavy-duty construction.
Finishing Washers
Finishing washers are designed to improve the appearance of exposed fasteners. They often have a countersunk shape that allows flat head or oval head screws to sit neatly in place.
Best for: Trim, cabinetry, furniture, and visible fastener applications.
Sealing Washers
Sealing washers include a rubber, neoprene, or EPDM component that helps create a weather-resistant seal. These are commonly used in roofing, siding, and outdoor fastening applications where water intrusion is a concern.
Best for: Metal roofing, siding, exterior panels, and weather-exposed fasteners.
Square Washers
Square washers offer more surface coverage than many round washers and are often used in wood construction. Their shape helps resist pull-through and can provide a stable bearing surface.
Best for: Timber connections, post and beam projects, and heavy wood construction.
How to Choose the Right Washer
Start with the application. For everyday fastening, a flat washer is often enough. For vibration, use a lock washer or another locking method recommended for the assembly. For soft materials or oversized holes, use a fender washer. For outdoor or wet applications, choose a washer material or coating that matches the environment.
Material matters, too. Zinc-plated washers are common for indoor or light-duty use. Hot-dip galvanized washers are better suited for many exterior applications. Stainless steel washers are often used where corrosion resistance is critical, especially in wet or harsh environments.
Washer Size Matters
A washer should match the fastener diameter. The hole needs to fit around the bolt or screw without being too loose, while the outside diameter should provide enough bearing surface for the material. Using the wrong washer size can reduce holding power or damage the work surface.
Final Thoughts
The right washer helps your fastener do its job. It spreads load, protects materials, improves appearance, and can help prevent loosening or leaks. For contractors, builders, and DIYers, keeping the right washer types on hand can make installations cleaner, safer, and more reliable.
Fasteners Plus carries a wide selection of washers and compatible fasteners for construction, repair, and industrial applications. Explore our washer options to find the right fit for your next project.
