Digging fence post holes calls for controlling the dimension and aligning the posts so a fence is properly placed and not askew. It requires certain tools, a way to exact measurement, patience and fortitude. Let’s take a look at the types of diggers and tools for the job, some of which you may already have.
The Tools for the Task
At a minimum, you will need these four tools:
- A post hole digger, also called a clamshell digger
- Tamper-end digging bar
- Tile spade
For safety purposes, here is a list of more items you might consider:
- Work boots
- Safety glasses
- Dust mask
- Hearing protection *
*For powered diggers, you may opt for hearing protection. Remember, if you have to raise your voice to be heard over the noise of anything, you should be wearing hearing protection. Irreversible hearing loss does not really show up until years after the damage is done. Be wise and protect it while you can.
Here is a further list of items that you will be glad you thought of including:
- 2-lb. sledgehammer
- Tape measure
- String or thin rope
- 1 in. x 2 in. x 8 ft. furring strip board (very inexpensive)
- Water pitcher or bucket
- Gravel or construction aggregate
The Right Post Hole Digger for the Job
For the different types of diggers, you will see from their descriptions that each one has specific applications from the simple manual, one-man operation to the fully powered mechanical option. The digger is possibly the most important part of building your fence.
Post holes must maintain their integrity of strength to be sure your fence is aligned and remains stable and secure. The diameter must be tailored to the size of stock you use as your posts. A 4 x 4 post needs about a 6-inch diameter hole that goes straight down. For this reason, you cannot just come at it with a shovel for that would be too wide a hole and very difficult to try to dig out.
Read on to learn more about the different types of diggers:
This is the typical tool most people are familiar with for digging holes for fence posts, mailboxes, flagpoles, birdhouses or other such posts that only need small diameter holes.
As you can see, they are designed like a pair of tongs with curved blades securely fastened to each handle and sturdy grips at the other ends. The secret to keeping this tool effective is in sharpening the business end of the blades. You plunge this baby into the earth. Sharp blades help immensely by cutting down on your hard labor.
Our best pick for manual post hole digger is the AMES 2701600. This tool features a measuring stick ingrained right into the handle, oversized grips that are cushioned to protect your hands and strong hardwood handles.
Another option is to go for the Bully Tools 92382 14-Gauge 5.5-Inch Post Hole Digger with Fiberglass Handles. The extra strength in these handles can give one a greater sense of power.
Manual diggers are the least expensive compared to the other mechanical models described here. If you keep your blades sharp and follow some basic rules as to wearing gloves, how you position your body and how you use the manual digger, you can accomplish more without wearing yourself out. More on that later.
Gas-powered post hole diggers are useful for boring larger holes when time is of the essence. This machine has a gasoline-fueled powerhead similar to what you find on some lawn mowers. This handheld auger has the kind of energy meant to turn larger augers to excavate soil, hard-packed clay and rocks while loosening the material for easy removal from the hole.
The caution with these engines is their power. They are powerful enough to overcome the handler’s strength, which can lead a gas-powered post hole digger to become buried in the ground. Obstructions such as rocks and roots can be enough for the auger to catch forcing it to come off course and even come out of the grip of the operator.
Handlers must keep the auger straight while guiding it down the hole it is creating. Once the auger gets dug into the ground, it can be difficult to extract it in order to right the auger’s orientation to resume digging.
Gas-powered diggers can use variable width blades. Wider blades bore wider holes, however, what you gain in power and width, you loose in depth. Most gas augers do not bore much deeper than a 3-foot hole, which can be sufficient for typical yard work.
Our best pick for gas power is the Southland SEA438 One Man Earth Auger with 43cc, 2 Cycle, Full Crankshaft Engine. It features a manual recoil easy start fuel delivery system so it starts with an easy pull. The wide detachable ergonomic butterfly handles provide better balance for one-person handling. The maximum depth is only 2.5-feet, though.
Unlike gas-powered augers, electric post hole diggers work on electricity or battery power packs. With a cord, you are limited to its reach, of course. With a battery, you are limited by how long the juice lasts. Either way, you have the similar option of variable width augers but with a little less weight than gas-fueled powerheads.
Your advantages further include none of the exhaust fumes, less noise, a bit more convenience and far less maintenance than what is required for gas-powered augers. Electric augers are useful for smaller yards or for holes that are within reach of the source of electricity.
Our best pick for an electric auger is the XtremepowerUS 1500W Industrial Electric Post Hole Digger Fence Plant Soil Dig Powerhead. Its motor delivers 90 ft-lb torque with 2,700 RPM impact rated speed with super comfortable, anti-skid, vibration-proof, ergonomic handles. It also has a safety lock feature to avoid accidental triggering.
For use on farms, ranches and by commercial contractors for extreme agricultural, industrial and commercial applications, hydraulic drive motors are the best option for extensive work that may be far afield. Compatible with flow rates of 10 – 30 GPM and hydraulic pressure up to 3,000 psi, mount kits allow for front end and skid steer loader applications.
Mount brackets are used to provide a swivel design for keeping the auger vertical during operation, Augers are available in sizes ranging from 6- to 36-inch diameters based on the model chosen.
Setting the Fence Posts
When it comes to filling the hole, you have choices today. You can go with the same dirt you pulled out of the hole, gravel, concrete or the latest invention, foam.
Using Dirt or Gravel
The option of gravel works best in heavier soil. It won’t work in sandy or loamy soil. The best method is to pour about five inches of crushed gravel into the hole once you have the post balanced. Then you tamp that down around the post before adding another five inches and repeating the process. You continue until you have reached the top of the hole. You can leave a little space around the top if you plan to grow grass around the post.
There are some considerations with concrete. You must be careful with the mix and make sure it is not too wet. You can either pour in some concrete first and then place and plumb the post, or you could pour in some gravel or aggregate and tamp it down, then place the post.
Concrete absorbs water. For this reason, it is best to use treated stock for the posts as this will help reduce the risk of rot. I personally do not advice using the quick method of filling the hole with dry, quick-set concrete powder and then just pouring the water over the top. In most cases, the water hardly gets absorbed all the way through. It is too much of a risk for all your hard work to waste it on this ill-advised short cut.
In the modern-day world of invention of which we could always use more, I suggest you might consider foam. The reason I am not shy about recommending high-density foam to set your fence posts is because utilities use this to set their poles. That said, consider the building codes. The compressive strength of foam is only about four percent of what concrete supplies.
The foam comes packaged in separate compartments of the bag and is activated when you bust the barrier and agitate the two separate parts together for at least 30 seconds. You must be prepared, though, as after that you must immediately deliver the goods.
The foam is still liquid at this stage and gets poured into the hole all around the post. It will expand to 15 times greater than its original mass in a matter of seconds. Another advantage is foam acts as a water barrier since it encapsulates the base of the wood post underground. The biggest drawback with foam is the cost. That $17.60 bag of expanding foam has to compete with a $6.00 bag of concrete.
Step-By-Step Guide for How to Dig a Perfect Fence Post Hole
First things first. This guide is meant to give you the high-points of how to dig a perfect fence post hole. You can make this process your own since you will be exerting the effort. The suggestions here are those that will hopefully leave you in good stead for conserving your energy and proving to be useful for expediting this function.
Step 1: Determine the Location of Your Post Holes
Before you even break ground, determine the location of your holes. Whether you start out with an estimation or go all out with the tape measure, string lines and marking off the center points of the intended post holes, your very next effort is to contact the local utilities.
Anytime you are penetrating the ground more than a few inches, you must first learn if there are any underground lines you must avoid. It would not do to haphazardly disrupt the local power lines for several reasons, not the least of which is your safety.
The next thing you want to check are the local building codes. It would do you no good to go through all the effort only to have to start over and do it again to correct any infractions. Yes, it seems like a bother but certainly far less than doing the work twice.
Step 2: Marking Off the Centers of the Holes
You can use a stake, a nail or a screw to mark the centers of the post holes. Spray paint or tape are good for marking a big “X” across the center of the hole. This is essentially the foundation of your fence. Keeping things aligned will give your fence the symmetry you are after.
Using the sledgehammer, sink the stakes upon which to attach a string line. This line can be used as a representation of the outside of the posts as they line up. In that sense, it will be the distance from the center to the outside of the post. For example, if you are using 4×4 posts, the center of the hole will be just under 2-inches from the string. More on this later.
Step 3: Initiate Digging Out the Center of the Post Hole
Carefully digging the topsoil with the shovel, you can establish a pilot hole by carving out a round divot or plug. You are creating the guide for yourself to follow with other tools to stay centered.
I know it is tempting to just go for it and use the shovel to dig out the hole. You are not digging a hole so much as you are preparing a stable shaft that will support your post for now and throughout the time it serves to hold up your fence. Your aim here is to maintain the integrity of the surrounding earth.
Step 4: Make Your Work Easier Using a Tile Shovel
This guide focuses on using the manual post hole digger. It helps to understand why this tool is not referenced as a shovel. It makes logical sense that one would think this tool should work as an efficient shovel, and it does in its way.
You can help yourself in the labor-intensive use of the digger by loosening the hard soil, clay or sand. The tile shovel is narrow for a good reason. It is possibly the best tool to help keep your hole plumb. It works as both a guide and as a shovel but notice, this is a long narrow shovel.
Even if you tried to use it like a traditional rounded shovel, it is impossible to dig in and try to pick up a shovel full of dirt. You just don’t have the room you need to make that move. You are better off thinking of it as a chisel, if you will.
Striking into the earth, you have a very small space upon which you can press your foot. So, don’t frustrate yourself. Take this process in steps. Loosen the soil using the tile shovel to help substantiate the shaft. It is typically the minimum width of a post hole, whether that is for a fence post, a mailbox, a flagpole or other posts.
Step 5: Use the Post Hole Digger to Remove the Fill
Once you have started the hole on center and loosened the soil, you can then start using the post hole digger to remove the soil. The digger works by holding the handles closed together and thrusting the points of the clamshell down into the soil. Working the digger back and forth, even turning it around and thrusting it in again can gain the advantage of grabbing more soil.
To scoop the earth out, you first separate the handles, which closes the clamshell around the loose soil. Then, pulling straight up, you can swing the digger around and deposit the dirt onto a tarp or into a wheelbarrow if you need to protect the lawn surrounding the holes.
A word of advice: Start with your feet apart about shoulder length, then be prepared to use your knees for movement and lifting. Also, your digger can be marked with measurements if it is not already provided on the handles to easily track your progress. If your soil is hard, you can add some water and allow it to settle into the earth. When you come back to it, you will find the soil easier to penetrate.
Finally, when working in loamy soil, you will find the post hole digger is inefficient at lifting out the sand as most of it slips out of the clamshell. Do not be above using your shop-grade vacuum to suck out the sand as you are descending into the hole. If you remove the filter, you should find it has more power.
Step 6: Interchange Use of Tools
The manual digger will continue usefully to remove dirt until you experience certain obstacles, such as roots and rocks. Both the tile shovel and the digger, when kept sharp for the work, may be able to dislodge and remove these. Otherwise, the digging bar is fashioned with a chisel end as well as the tamper at the other end.
Given its weight, it makes quick work of chomping through roots and even breaking rocks. Interchanging between these basic tools will reduce the physical struggle rather than sapping all your strength being limited to lesser tools for the challenge. You can also turn to a reciprocating saw when roots are too large to whack off with these tools. Just be prepared for any blow back from the motor as you could get it in the face. This is where your safety gear comes in handy.
Step 7: Tamping the Soil When You Reach Your Depth
Once you are reaching the depth of the hole that is half as deep as the fence is high, consider an additional 6-inches if you plan to use a gravel base. Whichever you decide, tamp down the bottom of the hole with the tamper end of the digging bar. This preparation will get your setting off to the right start.
Post hole diggers effectively have a maximum depth of roughly ¾ of their handle length. This means a five-foot pair is going to get you 3 1/2 -feet deep.
Some points to ponder: Check the local zoning for the frost line. Posts set in climates where it snows can cause the posts to be squeezed and thrust above the ground much as toothpaste gets squeezed out of the tube. Plan to dig a bell-shaped hope at least 6-inches deeper than the frost line. You can expect in these climate zones that a post hole for a 6-foot-high fence will have a minimum 9-inch diameter x 36-inch-deep hole. At the end, the hole should be down from grade or the ground surface by about 5- to 6-inches. You could say this is breathing room. You can back fill with dirt.
Step 8: Placing Your Posts
With your base prepared, you can set your posts. You are best served to plumb the posts using your plum line and level. The line when returned to its position should just be touching the outside of the post. You can use this line as a guide for placement. Using the furring strips, you can cross-brace the posts if you don’t have someone to hold them for you.
Step 9: Cementing Your Posts in Place
You cannot go an inch in your research to learn about setting a post in concrete without seeing everywhere the use of a quick-setting concrete mix poured dry into the hole then topped off with water. Voila!
I know it is even recommended by manufacturers of the stuff, but I do not advise this at all. The water tends not to reach the lower portions and the fit ends up being a crumbly liability. This method decreases the finished strength by as much as 80 percent. In time, the fence can lean or even fall over.
Let me just say, if you are going to use concrete, take the time to mix it first in your wheelbarrow. That said, I must add the caveat that you do not make the mix too wet. We are not making soup. You want it more the consistency of damp sand. Less water in this case is proper for set up. Too much water in concrete makes for a weak set up.
Start with six inches of gravel around the bottom of the post once it is set and plumb. Then add your concrete. If you can at all, angle the concrete at the base of the pole so that water drains away from the post rather than pools, you eliminate the risk of rot.
Step 10: Clean Up
I realize this is obvious, but I did want to make it to 10, and this is a good opportunity to remind you to take care of your tools. If you keep you post hole digger and your tile shovel sharp, you will always have an easier time using them. It is my contention why most people think digging post holes is the worst likely is due to inferior tools.
When you are prepared for a challenging project, such as digging fence post holes, having the right tools for the job makes it less of a struggle. Plan ahead for your layout, and check with the local authorities for building code compliance and utility lines.
Gather the appropriate tools and equipment to perform the task. If you have a helper, that makes things easier, but you can manage this task by yourself if you use this guide to help keep your mind on the significant fine points.
For grand projects, you might consider renting a power auger instead of using a manual post hole digger. Just keep in mind these machines are limited in the depths to which they can excavate. Also, you can exhaust yourself easily with a heavier machine if you don’t have someone you can partner with to keep the auger plumb and to haul out the soil.
For the most ambitious projects, the hydraulic auger makes this work look so simple it can make you cry. However, you must consider the relative expense.
To help illustrate the process, here are some videos that demonstrate how to use a post hole digger, the choice of concrete versus foam and why fence posts rot.