Boulders and drystone retaining walls blend together seamlessly in this Biltmore Forest stonework project built by Hammerhead Stoneworks.
Biltmore Forest Stonework: Before and After
This pair of images show how this stonework project evolved. The boulders were already in place, but ineffective at slowing erosion on the bank above. Mulch and leaves were constantly washing into the driveway. We decided for aesthetic and cost-savings reasons to leave the largest boulders and build our retaining walls to meet them. Smaller boulders were removed to make way for the retaining walls.
Stonework Project Getting Started
This image shows the calm before the storm. There’s about 9,000 pounds of stone there, (more than we need, but there are other projects planned we will use the excess for.) This is a drystone wall. Note the black geo-textile drainage fabric laid over the exposed bank. This fabric allows water to pass through, but captures silt and other fine particles that would wash through the wall. Drystone retaining walls are more beautiful and more durable than a mortared wall installed in the same situation. In effect, the whole wall is a drain, allowing rainwater runoff to pass through. Hydrostatic pressure never builds up. Hydrostatic pressure is a powerful force and is responsible for pushing over so many of the older, mortared retaining walls that we see around Asheville.
This image shows us making progress on the lower wall. The string line is level across, though the wall shrinks and grows as the driveway rises and falls.
Stonework Project Details
We used a metamorphic stone called gneiss, quarried in Fletcher, North Carolina. It’s a native stone and looks just right used for landscaping walls like this one. All of the stone is laid in its bedded plane, meaning the stones are set laying the same way they were formed. Face bedding (standing up) a stone like this can result in major problems, as water can work its way into the stone and cause layers to delaminate and peel away. In the background you can see a rough old wall, a jumble of stones really, that will someday soon be replaced with a wall like this one.