Manufactured blocks, poured concrete and landscape timbers are all good choices for building sturdy and uniform retaining walls, but if you want anatural look that blends with thelandscape, fieldstones may be the solution. Although building walls with large boulders is best left tocontractors with cranes and loaders, a fieldstone wall is a DIY-friendly project. You’ll save money on materials as well as labor costs, which can be high because of the challenges in working with irregular stones.
Understanding how to build a basic fieldstone retaining wall is easy; the labor is not. Fieldstones are deceptively heavy (see “Heavyweights,”), and building a wall with them is exhausting work, but the results are worth the effort.
Planning and layout
The first step is to determine the location and height of the wall. There are a couple of ways to approach building a retaining wall into a sloped landscape (see “Wall Position”). You can build the wall at the base of the slope and backfill the space behind the wall, or you can cut into the slope and redistribute the soil to other areas.
Walls built from stacked fieldstones should not be higher than 3 ft. If you need to create a taller wall, it’s best to either build multiple shorter walls that form terraces or use manufactured retaining-wall blocks that are engineered to fit together.
You’ll need roughly 1 ton of 6- to 12-in.-dia. stones to create 20 sq. ft. of wall area. The easiest option is to buy the stones from a landscape or stone-supply yard and have them delivered. Fieldstones are typically priced by the ton, and it’s worth shopping around for the best price. I found prices in my area ranging from $50 to $90 per ton. You might think hauling the stones yourself would be the best deal, but some yards charge a higher price per pound when you pick individual stones for small loads. It’s often cheaper to pay for a large single load to be delivered.
If you live in a rural area or you know a landowner who has fieldstones on his property, you may have a more economical option: Many farmers will let you have the stones for free if you’ll haul them yourself. The downside is that it’s more difficult to accumulate a large number of similar-size stones, and you’ll likely need to make several trips unless you have access to a large dump truck.
Building the wall
As a general rule, it’s best to build a retaining wall on a 6-in.-deep bed of compacted gravel for drainage and stability. This approach is recommended for fieldstone walls, but it’s not mandatory: The structural integrity of a properly constructed fieldstone wall will not be affected by minor shifting, and changes will not be visually apparent because the wall already has an irregular appearance. However, a compacted-gravel base that extends a few inches in front of the wall will help to prevent vegetation from growing into gaps between the stones.
The base trench should be deep enough to conceal one-third to one-half of the first row of stones. Include the depth of the compacted-gravel base if it is part of your construction plan.
Dig the base trench along the wall layout line. The trench should be 6 to 8 in. wider than the stones’ diameter. Use a
4-ft. level to check that the bottom of the trench is level. You can also use a shorter level that is attached to a longer piece of lumber such as a straight 2x4. The bottom of the trench should be undisturbed soil — don’t add soil back into the trench.
Cover the trench and cutback slope with a double layer of landscape fabric. The fabric will be a barrier between the stones and the backfill as the wall goes up.
The next step is to start placing the stones. Don’t build with stones larger than 14 in. dia. unless you have a device such as a tractor or hand truck to help move them (see “Helpful Haulers,” ).
Place the first row of stones in the trench. Start with the largest stones for the bottom row and use smaller stones on the top rows. The closer the stones fit together, the stronger and more attractive the wall will be. Roll the stones over to look at all sides, and try to find stones with profiles that fit well together. Take your time; this is more art than science. Whenever possible, try to position a flat surface facing up to create a level base for the next row.
Once the first row is in place, fold the landscape fabric over the top of the stones and backfill with a few inches of gravel next to the fabric and soil for the rest of the fill. Backfill up to the top of the first row; then roll the fabric back onto the slope.
Place the second row of stones. Overlap the front three-quarters of the second row over the back three-quarters of the first row, creating a 25 percent setback. Overlap or bridge the seams between the stones on the previous row. Continue to place rows of stones and backfill until you reach the finished wall height. After placing the top row, trim the landscape fabric so that a few inches are exposed beyond the stones; then backfill up to the top of the wall.
Once the wall is in place, you can finish the surrounding landscape. If grass will be planted right next to the wall, lay a few inches of mulch over the front fill gravel in front of the bottom row. The gravel and mulch will act as a barrier to help keep grass from growing into the gaps in the wall and makes mowing easier. Keep the grass back from the rock face by cleaning out this space and adding fresh mulch every few years.
Plants that require little moisture, such as varieties of small sedum, are the perfect choice to fill any large gaps between rocks. Cut the landscape fabric between the rocks and tuck the plants into the soil. You can create specific locations for these plants by intentionally leaving small gaps between a few of the stones. Stagger the gaps several feet apart to maintain the wall’s structural integrity.
Choose low spreading plants to place along the top of the wall, such as Blue Rug Juniper, varieties of vinca, creeping sage or creeping thyme that will cascade over the wall. Once it’s complete, the wall will require little or no maintenance other than caring for the surrounding plantings.
Northern Tool and Equipment
(1,500-pound-capacity tree truck, No.143722)
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