Learning to dig fence post holes in soft, sandy ground is hard enough – but doing it in rocky and rooty ground makes it much tougher. Rocks and roots present obstacles that will typically require hand digging to get around, so when digging with an auger, you’ll often need to bust out the shovel or digging bar to get the job done.
If you’re using an auger to dig fence post holes, then larger rocks can present a serious challenge. Smaller rocks are not an issue, as they’ll be picked up by the auger’s flutes, but larger ones can stop the auger right in its tracks.
When this happens, it pays to have a couple of hand-digging tools on hand. A spade, shovel, and heavy-duty digging/tamping bar will allow you to dig, pry or break up any large obstacles in your path.
Let’s take a closer look at the process of how to dig fence post holes in rocky ground, so you’ll be able to tackle even the toughest soil out there.
Tools & Materials Needed
- Digging/Tamping bar
- Post hole digger
- Spade and/or shovel
- Jackhammer (optional)
- Reciprocating saw (for large roots)
Digging Fence Post Holes in Rocky Ground – Guide
Digging fence post holes in rocky ground can be challenging, but is definitely doable. You’ll just need to prepare properly and have a few extra tools on hand. A digging/tamping bar which is a heavy 16-pound metal bar is one of the handiest tools for this job. These are ideal for breaking up or prying larger rocks free.
A post-hole digger is another handy tool for this, as it will allow you to manually dig through tough soil if your auger gets stuck.
Step 1: Remove the Top Layer of Soil
After you’ve mapped out the location of your post holes, you’ll want to remove the top layer of soil using a spade or shovel. The top layer should be relatively easy to remove when compared to the lower layers of soil, so you can remove it using a flat spade with relative ease.
Push the spade’s blade into the soil to cut through the sod and create the outline for your post hole. Pull the spade handle back to remove the sod, which you can hang on to until later for covering up the post hole at the end.
Step 2: Use Digging/Tamping Bar to Break Up Tough Soil
A digging/tamping bar will allow you to break up tough soil and rocks and turn it into relatively manageable soft soil. Once you have the perimeter of your soil established, there are a number of techniques you can use with the digging bar.
A good method of breaking up tough soil is to stand tall and using the chisel end of the tamping bar drive the weight of the bar into the ground as hard as you can. This is powerful enough to break through tough, clay-rich soil, and can even be used to break up and dislodge larger rocks.
You can also use your digging bar as a large lever to pry rocks loose. Hold it with the bottom portion lined up with the edge of your post hole and then pull on the digging bar to lever any rocks loose.
Large rocks may require you to use the digging bar to work around them, prying and breaking up the surrounding soil as you go. These larger rocks, when pried free, can actually remove more soil than you intended which will expand the perimeter of your post hole.
Step 3: Remove Large Rocks by Hand
When you’ve loosened up the soil and pried the larger rocks free, you can remove these larger rocks by hand. Smaller rocks can be left in place as they’re easy to remove using either an auger or a manual post-hole digger.
Step 4: Cut through any Large Sized Roots
Next, cut through any larger roots using a hand saw or a reciprocating saw. Cut them where they meet the edge of your post hole so they’re flush with the walls. These will present a serious obstacle to any auger or post-hole digger, so they’ll need to be removed manually.
Step 5: Repeat Until you Reach your Desired Depth
Depending on the depth of your fence post hole, you may need to repeat the above steps several times until you get down to your desired depth. When you have a significant amount of loose sand accumulated in your post hole, it becomes difficult to see what our doing, so remove the loose soil and then continue working.