Natural landscapes are captivating to nearly all people. What brings you to the outdoors? Perhaps being emersed in the beauty of the natural world provides us with a sense of wonder as we perceive the power of the landscape. Large trees and boulders among other natural formations are nearly unmovable by man. As homeowners, sometimes you want to bring that look and feel to your property. These features, as well, can serve in a practical way to reenforce the natural slopes of your property and help with erosion. If you don’t have a vision of how to achieve this, we can help you. One idea we recommend for clients is boulders or a boulder retaining wall for the following reasons:
- natural aesthetics
- retains soil/minimizes erosion
- adds character/unique structure
- locally sourced and available (less environmental impact)
- no glue or chemicals needed
- can prevent unwanted vehicle traffic
- fun and interesting way to highlight address
- use for sitting around outdoor living spaces
Once installed, the boulders may experience minor settling that happens within a year. In addition, if an area being retained is very steep (more than a 3ft tall wall), we wouldn’t suggest boulders to be installed without involving a structural engineer. Potential problems posed with retaining walls this height are from hydrostatic pressure build-up behind the wall and/or the way in which water flows can undermine the soil holding up a corner of a boulder.
Clients can be creative with the boulder arranging (we move and place), plant moss on the top of the boulders, or plant ferns/herbs/perennials around the boulders to highlight the natural beauty and give contrast to the structure.
It’s both an art and science. Specific goals are key with boulder installation. Depending on your goals, the size/color/type/arrangement of boulders will vary. It can be a fun process to pick boulders with a client (color preferences/unique bands in the rocks/funky shapes etc.). We as the professionals can help guide you to the balance and make sure your desires the needs of the project, and feasibility align with each other.
How we install and choose boulders:
For the first course of boulders, we usually set it on 6” compacted 21A base, and then start building the boulders up from there, as it minimizes the movement of the soil underneath. If you are concerned with dirt migrating in the gaps between boulders, we recommend installing about 1ft width of some sort of river rocks (we usually use mix color Delaware River rocks 1-3” sizes) behind the top of the wall, geotextile fabric, with 4” perforated pipe and 57 gravel to allow water to be captured behind the wall. This river rock buffer helps with less soil migration down-hill from the boulders.
We usually hand pick boulders per client/or per project. Each property has it’s own unique set of challenges. Access is a big part of choosing the right boulders for your property. We typically bring boulders from one of two different sources: light grey (Pennsylvania) PA boulders, and light bluish/color boulders that are sourced from Carrderrock Quarry in Bethesda Maryland and are called Carderrock boulders. We can either pickup boulders with our Bobcat Machine 595 to pickup the larger boulders, or our small Bobcat MT100 machine.