Fences on Concrete: Drilling vs. Deck Mounting

When you need to install  aluminum fences or a vinyl fences on a concrete surface, you have two installation options, drilling vs deck mountings. Which one will work best for your needs? Outside of the sprawling urban jungles of New York City, Los Angeles, and a few patches in between, most of the United States is blessed with plenty of green space. It makes you wonder why anyone would even consider putting a fence on concrete. However, it is not an uncommon request. Why is this? One of the most common applications for fencing on concrete is to fence off concrete driveways.

When to Put Fences on Concrete

Most long driveways could be more easily fenced by setting the posts in the ground just outside of the concrete, but many homes in cities or suburban areas have property lines ending at the edge of their concrete driveway. These shorter fences are used as a marker of the property line and to keep neighbors from parking too far over and blocking your driveway. They can also keep pets, children, and their associated toys in their proper yards. Other situations call for fencing over concrete as well. Another example is if you build a concrete pool deck for your backyard and want to fence it in. This is an excellent idea, and it keeps you and any wandering children or animals safe from being injured or drowned in your pool when you are not there to supervise. This would be another excellent reason to put fencing on concrete. Regardless of your reason, there are two methods of putting fencing on concrete: core drilling and deck mounting.

What is Core Drilling?

A core drill is a particular drill that removes a cylinder of material, such as concrete. It is similar to a hole saw. When these drills are used for concrete, they are usually called Diamond Core Drills, because their drilling end contains diamond segments. Diamond Core Drills are quite expensive to purchase, but you can rent them for much more reasonable prices. Once the core is drilled, you need to use a sponge to soak up any excess water left behind by the water-cooled drill. Then you can install the fencepost in place. The core drilling method places posts firmly in the concrete which allows for maximum stability for your fence and is recommended by most fencing suppliers.

What is Deck Mounting?

There are several variations for deck mounting your fence posts to concrete. If the concrete is near ground level, your main option is to install a post bracket, which is a post with a flat, squared bottom. The square has four small holes to drive concrete screws through with a hammer drill. This method is slightly less work and does not involve the expense of renting a Diamond Core Drill, but it is far less secure. In some cases, when the concrete slab is five or six inches above the ground level, you may be able to use concrete screws to attach a fence bracket to the side of the concrete instead of the top. This gives you more area inside your fence, but it is not any more secure. It is less secure because your support is divided between 4 thin concrete screws instead of the single post. There are multiple points of failure in the deck mounting option. The concrete screws can break. The deck bracket can break. The post itself can break (although this is not likely). All of these options can occur even if the concrete itself does not crack. The most common failure is for the concrete screws to wear away at the concrete around them and come loose.

Which is better?

Fence suppliers recommend using the core drilling method over deck mounting every time. It is a bit more expensive, but it provides you with far more security. With a single piece of metal in the concrete (the post) there are only two significant points of failure. Either the post can break (unlikely) or the concrete around it can be loosened up. However, even if the concrete around it breaks up, the fence will still be held in place by the inserted post. This problem can be easily remedied by reporting a small amount of cement into the post hole or even packing it with gravel or sand. If you are considering putting a fence over concrete on your property, you need to know that you have options available. However, due to safety and security of your fence, some options are better than others. Aluminum and vinyl fences work well in concrete, but wooden fences are not recommended for this task. Because wood swells and shrinks with heat and humidity, while concrete does not, wooden fences will tear themselves loose over time as they sit in concrete. Additionally, while core drilling and deck mounts are both valid options for installing your fence, core drilling is the better option. Core drilling will keep your fence investment safe and secure for years to come.
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