If you’ve ever stood across from a residential building after a heavy winter storm, staring at drift after drift of snow piled high against the eaves, you know two things: that snow isn’t just pretty—it’s heavy, and those drifts on roofs don’t just go away on their own. For 12 years, I’ve worked as a snow fence supplier, traveling from small mountain towns in Idaho to snowy suburbs in upstate New York, talking to homeowners, general contractors, and roofers who’ve dealt with the worst of winter’s impact on building structures. One question I get asked more than any other is this: Do snow fences actually change how snow accumulates on roofs? Snow Fence
The short answer is yes—but the how, why, and when is where it gets complicated. It’s not just about slapping a fence up and watching drifts form; it’s about understanding wind dynamics, snow properties, and how different fence designs interact with the weather patterns that move snow around. Over the years, I’ve tested and installed hundreds of snow fence systems, talked to civil engineers who specialize in snow load research, and learned from local veterans who’ve relied on these fences for generations. Today, I want to break down what we actually know about snow fences and roof snow accumulation, share what works, what doesn’t, and why choosing the right fence for a specific building makes all the difference.
Let’s start with the basics of how snow moves and accumulates on roofs. Most people don’t realize that nearly 90% of snow that falls in windy conditions doesn’t land straight down—it’s transported horizontally by wind, especially in areas with consistent winter gusts. Light, dry powder snow can be picked up and carried hundreds of feet at wind speeds above 10 mph, while wet, heavy snow moves much less, but still slides or drifts when wind is strong. On a roof, wind patterns change dramatically from the ground up: wind accelerates as it passes over a building’s roof edge, creating a small vortex right above the eave and slowing down as it reaches the roof ridge. That’s where snow tends to accumulate the most—along the eaves, the ridge, and on any overhangs—because that’s where wind speed drops enough to let snow fall out of the air and pile up.
Uncontrolled snow accumulation on roofs isn’t just a seasonal nuisance. The American Society of Civil Engineers (ASCE) estimates that a single square foot of wet snow weighs up to 20 pounds, compared to just 3 pounds for dry powder. A standard 2,000-square-foot roof can easily hold 20,000 to 40,000 pounds of snow during a heavy winter, and when that snow is unevenly distributed, it creates stress on roof trusses, gutters, and even the building’s foundation. We’ve all seen the news stories about collapsed roofs after a major snowstorm, and most of those cases aren’t just about too much snow—it’s about it being piled in the wrong places. That’s where snow fences come in.
Snow fences work by disrupting wind flow. When wind hits a fence, it splits into two streams: one that goes over the fence and one that goes under, creating a wake zone immediately behind the fence where wind speed drops by 50% or more. That slowdown is exactly what makes snow fall out of the air—instead of being carried past the fence, snow gets deposited in that protected zone. The key here is where you place that fence relative to a roof. If you install a snow fence far enough away from the roof edge, it will catch snow before it ever reaches the building, diverting drifts to an area that’s not on the roof. But if you place it too close, or if the fence is the wrong height, it can actually funnel snow directly onto the roof ridge—something we’ve seen happen more times than I can count when a roofer picks a cheap, flimsy fence without considering wind speed.
I learned this lesson early on in my career, back in 2011, when a general contractor in northern Vermont called me panicking. He’d installed 4-foot-tall wooden snow fences along the edge of a new housing development, just 10 feet from each roof’s eave. When we got the first big storm, we went out to check, and instead of drifts piling up in the yards, every roof had 2 to 3 feet of snow piled along the ridge. The wind had hit the fences, accelerated a bit over them, and then dumped all that snow directly onto the highest point of the roof. That day, I realized that snow fence design isn’t one-size-fits-all, and placement is just as important as height.
Since then, we’ve worked with civil engineers to test different fence designs and placement guidelines. The core principle we follow now is called the “10:1 rule” for roof snow fences: for every foot of roof height, you need to place the fence 10 feet away from the roof’s edge, measured along the ground. So for a building with a 10-foot wall, the fence should go 100 feet from the building—close enough to catch wind-carried snow before it reaches the roof, far enough away to avoid funneling it onto the roof ridge. That rule has held up in every climate I’ve worked in, from Minnesota to Colorado.
But not all snow fences are equal. There are three main types of snow fences we work with, and each has a different effect on roof snow accumulation. First, there are timber fences: solid wooden posts with wire mesh stretched between them, usually 6 to 8 feet tall. These are the most effective for high wind areas, because they create a very consistent wake zone and disrupt wind flow more evenly. Second, there are polymer mesh fences: lightweight, UV-stabilized mesh that comes in panels, usually 4 to 6 feet tall. These are cheaper than timber, but they don’t last as long (they’ll break down after about 10 years, compared to 30 for timber) and work best in areas with wind speeds under 20 mph. Third, there are portable snow fences, made of plastic or fabric, that are used for temporary installations, like at construction sites. These work well for single seasons, but they tend to sag in heavy snow, which reduces their ability to disrupt wind.
The biggest mistake I see customers make is choosing the wrong fence height. A fence that’s too short won’t create a large enough wake zone to catch all the wind-carried snow, so snow will still make its way to the roof. A fence that’s too tall can create larger vortices, which might dump snow too far back from the building, but in some cases, can also pull more snow toward the roof edge. Our standard recommendation for residential buildings is a 6-foot timber fence, because it balances coverage and wind disruption for most climates. For commercial buildings with steeper roofs or higher wind speeds, we usually suggest 8-foot fences, because taller fences create a larger protected zone.
Another factor that affects snow accumulation is snow density, which varies a lot by location. In places like Montana or Alberta, where winter snow is dry and light (often called “powder”), snow is carried much farther by wind, so snow fences need to be placed a bit farther from the building, and be taller, to catch all that moving snow. In areas like the Pacific Northwest, where snow is wet and heavy, wind-carried snow moves less, so shorter fences placed closer to the building work just as well. We had a customer in Seattle a few years ago who tried a 6-foot fence 50 feet from his roof, and it worked perfectly—because the wet snow only moved about half as far as the dry powder we see in Idaho. That’s why we always ask customers to tell us about their local winter weather, average wind speeds, and what kind of snow they usually get, before we recommend a fence.
It’s also important to note that snow fences aren’t a perfect solution for every roof. If your roof has a very low slope (less than 3:12, meaning it rises 3 feet for every 12 feet of horizontal length), snow is less likely to slide off on its own, and snow fences can help prevent large drifts from forming, as long as they’re placed correctly. If your roof has a steep slope (over 12:12), snow will naturally slide off in smaller loads, so snow fences are less critical, but they can still help prevent ice dams, which form when melted snow refreezes along the eave. Ice dams are a huge problem—they can cause water damage to ceilings, walls, and insulation, and snow fences reduce the amount of snow that melts on the roof, which in turn reduces ice dam formation.
Wait, let’s get back to the science to make sure we’re not just talking from experience—there’s research to back all this up. A 2021 study from the University of Alaska Fairbanks’ Geophysical Institute tested snow fence systems in interior Alaska over three winters, measuring snow accumulation on roofs both with and without fences. The study found that when fences were placed at the correct 10:1 distance from the building, roof snow loads were reduced by an average of 40% compared to roofs without fences. When fences were placed too close or too short, roof snow loads actually increased by up to 25%, confirming what we’d seen in Vermont a decade earlier. Another study from the National Institute of Building Sciences looked at ice dam prevention and found that properly installed snow fences reduced ice dam occurrences by 65% in residential buildings, because they cut down on the amount of snow that sits on the roof long enough to melt.
Over the years, we’ve also learned about maintenance, which is just as important as installation. A snow fence that’s covered in fallen leaves, or has sagging mesh from snow loading, won’t work. We recommend inspecting fences every fall, before the first snow, to tighten any loose posts or replace damaged mesh. In areas with high humidity, timber fences can rot if they’re not pressure-treated, so we always use ACQ-treated wood, which is resistant to rot and insects. For polymer fences, we recommend choosing panels with a high tensile strength, so they don’t tear in strong winds.
I know it’s tempting to try to save money by using a cheap fence from a big-box store, but in my experience, that’s a false economy. I’ve heard too many stories of homeowners who bought a $100 portable plastic fence, only to have it blow away in the first storm, or sag so bad by mid-winter that it stopped working, leading to thousands of dollars in roof repair. A good snow fence is an investment in your building’s longevity. A properly installed timber snow fence costs between $3 and $5 per linear foot, including installation, and will last 30 years or more—compared to repairing a roof, which can cost $8,000 to $15,000 for a standard home.
At the end of the day, snow fences don’t eliminate snow on roofs entirely—some snow will still fall on the roof, no matter what. But what they do is change the way snow accumulates, reducing uneven drifts that put stress on roof structures, and cutting down on ice dams that cause water damage. The key is working with someone who understands the science, and who will tailor the fence to your specific location, not just sell you a one-size-fits-all product.
If you’re a homeowner planning for this winter, or a general contractor working on a project in a snowy climate, I’d encourage you to reach out to talk through your needs. We don’t just sell fences—we work with you to figure out the right height, design, and placement for your building, based on your local wind and snow conditions. Whether you’re dealing with a small residential roof or a large commercial building, we can help you find a snow fence system that works for you, and lasts for years to come.
Heavy Duty Snow Fence References
American Society of Civil Engineers (ASCE). 2016. Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE 7-16).
University of Alaska Fairbanks Geophysical Institute. 2021. Snow Fence Efficacy for Reducing Roof Snow Loads in Interior Alaska.
National Institute of Building Sciences. 2020. Ice Dam Mitigation Strategies for Cold Climate Buildings.
U.S. Department of Agriculture Forest Service. 2018. Snow Management Practices for Rural and Urban Structures.
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