The Dos and Don’ts of Setting a Fence Post

It’s a bona fide do-it-yourself classic: Every summer without fail, legions of homeowners grab their toolbox and head outdoors to erect a wood fence. Putting up a fence is a substantial, satisfying project, and particularly if you’re relying on a kit, an eminently doable one. And if you’re fortunate enough to have level terrain to work with, there’s really just one tricky step—setting the posts. As they say, a fence is only as strong as its posts. If they fail, the rest of the fence will follow suit, so it’s crucial to devote special care to setting them properly. Anything less, and you run the risk of having to set the fence posts all over again in only a few years’ time. The good news? Setting a fence post doesn’t require uncommon skills or expensive tools, and doing it right doesn’t really take much longer than doing it the slapdash way. Whether your goal is privacy, a better-defined property line, or simply a beautiful addition to your yard, a fence can fit the bill. But to ensure pleasing, long-lasting results, you’ll need to keep a few select considerations in mind and avoid a handful of potential pitfalls. Read on for the full details.

DO Select the Right Type of Wood

Remember that different types of wood offer drastically different levels of long-term fence-post performance. Pressure-treated wood, which boasts both durability and affordability, ranks high among the top choices. Also commonly used—and considerably more expensive (although prices vary by region)—are beautiful, naturally resistant species like cedar, cypress, and redwood. All contain resins that forestall the harmful effects of pests and moisture. Other species, including spruce, oak, and pine, may be used with confidence only if treated beforehand with a brush-on preservative (look for copper naphthenate on the list of ingredients). Generally speaking, it’s wise to opt for darker, denser heartwood over younger, lighter-colored sapwood, because heartwood harbors better defenses, particularly against wood-boring insects. Finally, no matter what wood you select, be sure that you’re buying lumber labeled as suitable for in-ground applications.

DON’T Make Postholes Too Small

Building codes and ordinances in your area may stipulate a legal depth and diameter for fence-post holes. If not, conventional rules of thumb offer a reliable guide. Typically, in part to ensure that posts lodge below the frost line, experts call for a hole deep enough to submerge the bottom third of the post below ground. For a six-foot-tall post, therefore, you would dig a hole two feet deep. The ideal diameter, meanwhile, should measure three times the width of the post. So, for a standard 4×4, the ideal hole would span twelve inches across. It’s important to note that fence-post holes must be flat-walled and barrel-shaped, maintaining a consistent diameter from top to bottom. If you use a regular shovel, you’ll end up with a cone-shaped hole. Instead, make quicker and easier work of the task by opting for a posthole digger (available for rent at your local home center). Otherwise, use a clamshell digger, which will be slower going but equally effective, particularly if you’re working with rocky soil.

DO Employ a Base Gravel Layer

If a fence post fails without any sign of a pest infestation, it’s likely that the failure was caused by moisture that rotted the wood over time. To help slow such deterioration, add pea gravel or crushed stone to the bottom of the posthole. Once you have added gravel to a depth of three inches or so, use a piece of scrap lumber to tamp down the layer. Next, pour an additional three inches of gravel into the hole, tamping down a second time. This simple measure goes a long way toward helping rainwater drain freely into the subsoil. It works so well, in fact, that in mild climates, builders sometimes elect to set fence posts with gravel alone. While that approach makes sense in certain situations, for a lasting installation, experts are more likely to specify a combination of gravel (for drainage) and concrete (for much-needed stability). One type of concrete works particularly well in such applications—rapid-setting concrete like category favorite CTS Rapid Set Concrete Mix.

DON’T Ready the Wrong Amount

True to its name, rapid-setting concrete doesn’t delay. In fact, CTS Rapid Set Concrete Mix sets in only 15 minutes. That being the case, it’s only practical to plan your approach. First, consider the size of the posthole in relation to the concrete yield. A standard 60-pound bag of CTS Rapid Set Concrete Mix yields approximately 0.5 cubic feet, so depending on the volume of your hole, you may need to prepare multiple bags at once. Just be careful not to mix more concrete than you can put in place in 15 minutes, before it begins hardening. After you determine how much concrete to prepare, proceed to combine the mix with water, adhering to the precise ratio printed on the package. Continue mixing for two or three minutes until you’ve achieved a smooth, lump-free consistency. At this point, with the post set in place, you can begin filling the posthole with concrete. Pack the concrete to a level slightly above the surrounding soil. Here, to prevent pooling, trowel the concrete so that it slopes away from the post. Double-check that the post hasn’t fallen out of level, then let the concrete harden.

DO Apply Caulk to Each Fence Post

After only an hour, CTS Rapid Set Concrete Mix will have hardened completely. You might consider the job done, but to further safeguard the fence post against rot, there’s one more important detail to address. Begin by inspecting the area where the post juts out of the hole. Do you notice a seam? Left as is, this seam could invite water to become trapped in any slivers of space between the wood and the concrete. Over time this moisture could lead to rot—but this scenario isn’t inevitable. After all, there’s a simple means of sealing the opening—caulk. Be proactive: Once the concrete has hardened, go ahead and apply exterior acrylic latex caulk directly to the seam, all the way around the post. (Alternatively, you can use any silicone caulk that adheres to concrete.) Be forewarned that the accumulated effect of freeze-thaw cycles may cause the seam to widen, so you’ll probably need to recaulk every now and then.

DON’T Neglect to Do Due Diligence

Be responsible. Before getting underway with your project, consult with municipal officials to confirm that your planned fence doesn’t deviate from any specifications of relevant building codes or ordinances. Some localities enforce strict regulations. Also, as you would for any project that involves digging deep down in the dirt, dial 811 (or visit call811.com). Do this about a week before you plan to start the work, so the utility company will be able to come and mark the approximate location of any lines that run under your property before you begin digging. Make no mistake: Digging can be downright dangerous if you don’t know what lies a foot or two below the ground. As long as you give a wide berth to any buried lines, you should be perfectly safe. As for the posts themselves, a little regular scrutiny and maintenance will help ensure a long life for your fence. Inspect your posts at least once a year, ideally in spring or fall, and reapply paint or stain as necessary to protect the wood and keep your fence looking its best.

This article has been brought to you by CTS Cement | Rapid Set. Its facts and opinions are those of BobVila.com.