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Thursday, August 10, 2017

The Best Fencing for Cold Climates Remains Solid in Wind, Rain, and Snow

When my parents got their first home the backyard wasn’t fenced in, and being a young couple who’d just bought their first home, they decided to save money by building a fence themselves. It went up in the spring, and it worked great all through the summer and into the fall. One December morning my dad got up, let the dog out, and watched her cheerfully run over the fallen fence into the neighbor’s yard and then into the street beyond. It took a good part of the morning to bring her back inside. Obviously a fence that falls down isn’t the best fencing for dogs that jump, dig or run.

My dad, never the most diligent man at the best of times, had predictably taken shortcuts building the fence. Instead of bothering to check the frost line where we lived, he’d settled for burying the posts two feet deep and calling it a day. As the cold weather came, the moisture in the soil froze, causing it to expand and push the posts out of their holes (this is a process called frost heaving, or jacking). Deep into winter, a strong wind came up and the whole fence--along with its loose posts--went down. My father’s experience begs the question: what exactly is the best fencing for cold climates, and how should it be installed so that it stands up to tough winters?

Cold Climates Bring Challenges for Fences

 The basic idea behind frost heaving is that, because water expands when it freezes, the water in soil exerts an upward thrust on things buried in it--like fence posts and deck footings--as it solidifies. There are different solutions to this issue, but the most common recommendation is to ensure your posts or footers go at least a couple feet beneath the frost line. You can call your local city permitting office to find out how deep that is in your area. Now, even if you dig that deep, some frost heaving may occur—especially with posts sunk in the ground—as the frost acts on the part of the post above the frost line. The surest solution is to pour concrete footers below the frost line that are wider at their base than at their top. This way, the expanding frost helps to lock them in place rather than work them loose. But the challenges that winter brings to your fencing don’t stop once you get above ground level. Winter can affect the fencing material you use, causing it to break down or become fragile.

Winter affects wood mainly because it changes the humidity content of the air (air tends to be much drier in winter than summer), causing wood to shrink. Periods of wet followed by periods of dry weather can also cause cycles of shrinking and expanding that will push fasteners like nails and screws out of the fence, and can cause boards and rails to come loose. Some materials, like vinyl fencing, are made of a material that doesn’t absorb water. Yet, as temperatures drop plastics enter a glassy state and become more brittle, making them prone to snapping upon sudden impacts (like slipping on frozen ground and trying to catch yourself on the fence). This makes PVC a less-than-perfect choice for fencing in a cold clime.

What Material Makes the Best Fencing for Cold Climates?

 So what fencing material does do well in cold weather? From a purely structural standpoint, metals are the best material for cold weather fencing. The molecular structure of metals doesn’t absorb water, so they’re not as vulnerable to moisture-based swelling and shrinking. That’s not to say that water can’t work its way inside a metal fence, or that metal doesn’t contract. But water simply doesn’t saturate metals in the same way it does wood. There are a couple of fencing options that take advantage of this:

  • Wood fences with metal posts have wooden pickets that are subject to the same water absorption and other problems as your average wooden fence. But by not depending on wooden posts to hold them up, the structure of these fences is sounder and lasts longer. A wood fence with metal posts should stay up through at least a few winters.
  • Steel fences are steel through and through, with steel top rails, pickets, and posts. These are the fences that people are thinking of when they talk about a wrought iron fence. No parts of steel fences are prone to water absorption, but water can collect in joints and around fittings. It is very rare that expansion or contraction problems affect these fittings, but it can happen. Typically, steel fences have spaced pickets that allow strong winds through, making them good fences for windy areas such as the Great Plains and the coasts.
  • Aluminum fences share many of the same properties as steel ones. They, too, are built with an eye toward the “wrought iron” look. These fences, however, are a lot lighter than their steel counterparts, and easier to install. There is a tradeoff in strength, though. Depending on the quality of the fence, aluminum fences can be more prone to denting and bending than steel is. A more critical winter issue is galvanic corrosion, in which a high salt environment (like an area near a salted road in winter) creates a reaction between the steel fittings and the aluminum fence, causing the aluminum to corrode.

These fences are built to withstand many of the challenges of winter weather, at least structurally. Aesthetically, there may be other issues. While a wooden fence on metal posts can stay up through winter, its handsome youth will likely be short-lived. The wood fibers of the pickets are forced apart by repeated expansion and contraction throughout the winter, forming areas where mold and rot can take hold. On lower-quality metal fences, the protective coating may crack and flake off as the metal contracts and expands with the temperatures, leaving the bare metal vulnerable to rust.

Fences That Look Good Through More Than One Winter

 Due to the issues that wood, vinyl, and aluminum fencing have in cold weather, steel is generally the choice that will stand up best to winter year after year. Steel does need more than a thin coat of paint to do that, though, and not all steel fences are created equal. There are several types of coatings that preserve steel from rusting away, and it is best to understand a little about them before you go looking for a steel fence:

  • Pre-galvanization: Most steel that is meant for outdoor use is pre-galvanized right at the steel mill. This coat is a thin layer of zinc applied to the stock metal. You can actually see an example of this on most chain link fence posts. The mottled pattern you see on these posts is actually crystallized zinc. This pre-galvanization layer protects the metal from moisture which could cause rust, but it is very thin and can be easily scratched off. Cutting and welding in fabrication will actually remove the galvanization around the cuts and welds.
  • Hot-Dipped Galvanization: This method involves adding a post-fabrication coat of zinc. In this process an entire piece, once assembled, is then dipped in molten zinc to coat it. This type of galvanization is much thicker than the pre-galvanization coating that is usually applied straight from the mill, and it lasts longer. It is the industry-wide standard for small hardware such as outdoor screws and bolts. It is a sacrificial coating, meaning that as long as some zinc remains on the steel, the zinc will corrode instead of the steel. HDG is a rugged coating and works well on heavy-duty objects, but for something like a fence, the corrosion of the thick layer of zinc as it is ‘sacrificed’ can affect the paint or powder coating on top of the metal, causing unattractive white patches to form.
  • Electrophoretic deposition: Also called an e-coat, this is an alternative to hot-dipped galvanization which uses a non-metallic coating. Effectively, it is a method of coating that relies on the e-coat particles having an opposing charge to the piece being coated. These particles are attracted to the metal due to this opposite charge and form a thin, uniform layer over it. E-coating creates a smooth, extremely durable, moisture-proof and non-sacrificial layer that can be safely coated with a paint or powder coat without any danger of galvanic corrosion. For this reason, the automotive industry uses this method of rustproofing on the underbellies of cars. The fact that e-coatings are designed to protect against road salt and other corrosive materials makes e-coated fences perfect for coastal areas.

All of these coating systems are aimed more at rustproofing than they are at appearances, which means that once these coatings are applied, your fencing will need to be coated with an aesthetically appealing coat. Now, it is possible to paint over any of these coatings with traditional paint, but this generally doesn’t work into the joints very well. Even with a primer coat, the odds are pretty good that the paint will still end up peeling off sooner or later. A better option is powder coating, which is applied as a layer of powder and then baked on to the metal. This forms a uniform layer that can vary in thickness as desired and tends to last quite a bit longer than traditional paint on most surfaces.

The long and short of all this is that the best fencing option for cold climates is e-coated steel that’s been powder coated. Without the heavy galvanization layer, the fence won’t end up with zinc coming through the paint, and the powder coat will stay smooth and beautiful no matter what. This combination, though, can be hard to find. Most fencing features only pre-galvanization to protect it from moisture, sometimes with a powder coating on top, through which moisture usually makes its way eventually. Almost no one uses e-coatings to really rust-proof a fence and keep it looking nice.

One of the few companies that do this is Fortress Building Products, with their line of thoughtfully and thoroughly engineered building products. Fortress orders pre-galvanized steel to make its fencing, adds a zinc precoat, and, once it is assembled, e-coats the fence panels before applying a layer of high-quality powder coat. These multiple coatings, and especially the unique e-coat, help ward off galvanic corrosion and corrosion due to atmospheric moisture, keeping their steel fence systems looking nice winter after winter even in the coldest climate.



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