How to Build a Mossy Dry Stone Patio
Chronicling my geological walk through time
By Brian Estill
I recently embarked on a project that I thought would take a week, but, instead, took several: laying a mossy dry stone patio. Replacing the ugly mud in my own backyard became quite the project. Here’s how I approached it.
When I began this project of building a mossy dry stone patio, the previous homeowners had already excavated the dirt and had fist-sized rock in the area. It was around 2 to 4 inches deep. I tried to excavate 2 more inches. However, that proved difficult without a machine. The dirt was compacted enough to hold the stone. You should excavate your area to 4 inches as best you can.
Order Dense Grade Aggregate (DGA) rock. Forget the sand. Ideally, you want a base of 2 inches of DGA to lay on. However, since creek stone is different widths, you don’t want to tamper the whole thing 2 inches at once, as I did. Set the stone by smacking it good with a rubber mallet.
Some of the stone will be lying in the hard dirt; most will not. The DGA acts sort of like a stone by itself. It compacts so tightly that when it is struck by the mallet it will become one with the rest of the material around it. Water still is allowed to pass through it, however.
Go to your nearest stone yard and select the stone. The bigger the stone, the better. Look for stone with fossils or other traits that give it character.
Fill up a 5-gallon bucket with the DGA, and pour it where you want to begin. Remember that walkways and patios aren’t level, and water is not your friend when it comes to most buildings. Water needs to flow downhill around a ¼ inch per foot.
Let’s talk about tools for a moment. You ought to have a hammer drill with the point chisel and flat 1-inch chisel, as well as a grinder with a 4-inch blade.
In case you’re new to stone cutting, allow me to give you a quick lesson. First, you make a valley. You do this with either the saw or point chisel. Next, you use a 1- or 2-inch flat chisel to tap on the valley (not hard just taps). Go around the entire stone tapping. Then, tap harder. When it breaks, it will be at that line.
A faster way to do this: Buy a Block Shear Stone Cutter, like I did. It’s expensive, but worth every penny, since you’re a Pro and will use it for years.
Say you’re laying stone tightly against the next stone. You have one that almost fits, but is too thin. What do you do then? Pour 2 or 3 inches of concrete into the hole before laying the skinny stone.
Reflect on what you have done. You have mastered how to shape the stones. The patio or walkway looks like a beautiful mosaic. To assure you keep that natural, dry creek stone look, see Step 7.
A master’s touch is the finishing step to build a mossy dry stone patio. I researched how to grow moss and I think you should, too. Collect moss in your area, scraping off any dirt. In between the stones of your walkway, place a mixture buttermilk (yes, buttermilk) and soiled moss. Squish it into the joints.
Around the high-low spots on your patio, use your point chisel to knock off the high points. You want easy transitions and natural flow on your patio or walkway. If you have a sand blaster, use that after knocking the high point off to give it a natural “erosion” look. A grinder with sand paper will work too, if you go slowly and don’t bare down too hard on the stone.
There is a geological element to my patio that is quite unique. The Kentucky state fossil is the Brachiopod. A Brachiopod is a shell-like mollusk that is 500 to 550 million years old.
Some species of the crinoid fossils, which are 350 million years old, continue as living fossils to this day. The asphalt is from 2017, so in nine steps from the asphalt to the deck, you’ll cross millions of years. Projects like building a mossy dry stone patio could be used as teaching tools for children to get them interested in earth sciences and the masonry trade. And, if we can inspire young minds, we have done much more than build a stone
Brian Estill is owner of Estill Masonry Artworks in Louisville, Ky., EstillMasonryArtworks.com.