If you’ve ever browsed a hardware store’s fastener aisle on a rainy Saturday, chances are you’ve walked past a stack of washers and not given them a second thought. I’m a supplier of washers—steel, stainless, nylon, the works—and for years, I’ve heard the same question come up from contractors, DIYers, and even small industrial teams: “Can these washers even hold up outside?” It’s a fair question. Outdoor applications expose every part of a build to something most indoor projects never see: salt spray, UV rays, fluctuating temperatures, rain, and dirt that gets ground into every seam. So let’s break this down, no stuffy engineering jargon, just the real-world stuff I see come through my warehouse every day. Washers
First, let’s start with what a washer actually does, because understanding its job makes it easier to see why outdoor use can go wrong. A washer’s two core purposes are: to distribute the load of a bolt or nut so it doesn’t pull through wood, plastic, or thin metal, and to act as a barrier between two materials to prevent galvanic corrosion. Galvanic corrosion, for anyone who’s not deep into fastener specs, is when two different metals touch in the presence of moisture—they start to eat each other alive, like two bullies picking on the weakest one. A washer acts as the middleman here, stopping that contact. But for that middleman to work outside, it has to hold up to the same harsh conditions as the rest of the project.
That’s where the biggest mistake people make: grabbing the cheapest steel washer from the hardware bin and slapping it on a deck or a fence post. Plain carbon steel washers are fine for a indoor shelf bracket or a lawnmower’s carburetor, but leave one on a coastal deck or a fence post that gets rained on weekly, and you’ll be replacing it before the first winter. Carbon steel rusts. Rust expands, prying apart the wood it’s meant to fasten, and the rust itself eats through the fastener it’s paired with, too. I once had a contractor come into my shop, panicking, because he’d installed a $10,000 outdoor deck using standard steel washers. Six months later, the washers had rusted so bad the deck boards were starting to separate. He ended up replacing every single washer—costing him more in labor than the initial savings on cheap parts.
So what washers actually work for outdoor applications? Let’s go through the common types I supply, and where each belongs, because not all outdoor jobs are the same.
Stainless steel washers are the workhorse here. Specifically, 304 and 316 grades. 304 is the most common, good for general outdoor use—deck rails, fence posts, backyard shed doors—where moisture is occasional, not constant. It resists rust and galvanic corrosion as long as it’s not touching something like aluminum, but if you’re on the coast? 304 might not cut it. Saltwater is a harsh enemy. I saw a customer last year use 304 stainless washers on a dock piling in Florida. By the end of the first year, the salt spray had pitted the washers so badly they lost their load-bearing capacity. That’s when 316 stainless comes in. It’s alloyed with molybdenum, which makes it resistant to chloride corrosion—perfect for coastal docks, boat lifts, or any application within a mile of the ocean. It’s a bit more expensive, but I always tell customers: a $0.10 washer that lasts 10 years is way better than a $0.02 washer that needs replacing every two.
Then there’s nylon washers. These are non-metallic, so they eliminate galvanic corrosion entirely, which makes them great for pairing with aluminum, a metal that reacts badly with steel. I use nylon washers a lot for outdoor window frames, RV slides, or any project where two different metals are in constant contact. Nylon doesn’t rust, it’s resistant to mild UV exposure (though you don’t want to leave it in direct sun 24/7 for years), and it won’t scratch soft materials like aluminum siding. The catch? Nylon breaks down in extreme heat. If you’re building a deck around a wood-burning fire pit, don’t use nylon washers—they’ll melt. Stick to stainless there.
Another type people overlook is zinc-plated washers. Wait, don’t write that off—if you use the right zinc coating, they can work for mild outdoor use. The key here is “hot-dip galvanized” vs. the cheap electroplated stuff. Electroplated zinc is a thin coating that scratches off the first time you tighten a bolt, leaving the steel underneath exposed to rust. Hot-dip galvanized washers are dipped in molten zinc, creating a thick, durable coating that lasts much longer in rain and mild humidity. I sell a lot of hot-dip galvanized washers for chain-link fence installations, where the budget is tight but the job needs to hold up. Just make sure you pair them with a fastener that’s also galvanized—same as with stainless, mixing galvanized and uncoated steel will cause corrosion.
Now, let’s talk about the applications where washers absolutely can be used outdoors, but with some caveats. Let’s start with residential projects: backyard decks, garden fences, outdoor tool sheds, patio furniture. For these, 304 stainless or hot-dip galvanized washers are standard. I recommend checking the fastener’s rating, too—if the bolt you’re using is rated for outdoor use, make sure the washer matches that rating. For example, a deck bolt that’s “pressure-treated wood rated” will pair with a washer that can handle the preservative chemicals in the wood, which can be corrosive too. Pressure-treated lumber has come a long way, but old habits die hard—still, don’t use cheap steel washers there.
Then there’s commercial and industrial outdoor applications: warehouse loading dock doors, agricultural equipment, playground equipment, road guardrails. These are the jobs where I see people pushing washers to their limits. Playground equipment is a big one—kids are hard on hardware, and rain + dirt + constant use means washers need to hold up. I supply 316 stainless for commercial playgrounds, because not only does it resist rust, but it’s smooth, so it won’t catch on clothes or skin. Agricultural equipment, on the other hand, is exposed to fertilizer chemicals, mud, and constant temperature swings. Hot-dip galvanized washers are popular here, but a lot of farmers also use 316 for parts that are near water or salt, like irrigation lines.
But here’s where it gets tricky: some outdoor projects should not use certain washers. Let’s list the no-gos. First, plain carbon steel washers, as I mentioned earlier—they will rust, plain and simple, no matter how much you paint over them. The paint will chip, the rust will come through, and you’ll end up with a failed fastener. Second, uncoated aluminum washers. Aluminum is soft, so it compresses over time, losing its load-bearing ability. It also corrodes in contact with moisture, and when it corrodes, it creates a white powder that eats away at the fastener. Third, low-quality nylon washers. Some discount nylon washers break down after a few years of UV exposure, getting brittle and cracking. Always look for washers that are rated for outdoor UV resistance—you’ll see that on the packaging, usually as “UV-stabilized nylon.”
I get a lot of questions about whether you can reuse washers outdoors. The short answer is: don’t. Once a washer has been installed outside, it’s already been exposed to moisture, UV, and dirt. Even if it looks fine, the load-bearing capacity is compromised. I’ve had customers try to reuse old washers from a fence they took down, only to have the new fence fail a year later because the old washers had already corroded. It’s just not worth the risk.
Another common myth: “Any stainless washer works for outdoor use.” No, grades matter. 304 vs. 316 is a difference of life expectancy by years, especially in harsh environments. I had a builder come in last month who had used 304 washers on a project in South Carolina, near the coast. He’d noticed pitting, so he swapped to 316, and the same project three years later had zero issues. It’s not that 304 is bad—it’s just not built for salt spray, humidity, and constant coastal conditions.
Now, let’s talk about real-world examples, because that’s what matters. Last year, I worked with a marina owner in Georgia who needed to repair his boat slips. He’d been using cheap washers before, and every two years, he had to replace the bolts and washers. I supplied him with 316 stainless fender washers (larger diameter, to distribute load better) paired with 316 stainless bolts. A year later, he called me to say it was the only repair job he’d done that didn’t need touching up. He ended up ordering another 5,000 washers for his other slips.
On the flip side, I had a homeowner last summer who tried to save $20 on washers for his backyard fence. He used standard steel washers, and by the end of the first winter, the washers had rusted so badly the fence posts were leaning. He had to tear the whole fence down and redo it with stainless washers, costing him three times the initial savings. That’s the kind of mistake I see all the time, and it’s why I always stress to customers: the washer isn’t an afterthought, it’s a critical part of the outdoor build.
So, can washers be used in outdoor applications? Absolutely—if you pick the right type, match it to the environment, and don’t cut corners. The key is to treat your washers like the important fastener component they are, not an afterthought grab from the hardware bin. Whether you’re building a small backyard deck or a large industrial dock, the right washer will make your project last longer, save you money in repairs, and keep everything safe.
If you’re working on an outdoor project and aren’t sure which washer is right for your needs, don’t guess. Reach out to discuss your specific application, environment, and load requirements. We’re here to help you pick the perfect washer for the job, no jargon, no hassle.
Hex Nut References
ASM International. (2006). Corrosion: Understanding the Basics. ASM International.
ASTM International. (2018). Standard Specification for Washers, Steel, Mechanical. ASTM F436-18.
National Association of Home Builders. (2020). Outdoor Fastener and Material Guide. NAHB Research Center.
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