Building a Flagstone Patio

A gardening client asked me to build her a flagstone patio this July to help prevent her three Cairn Terriers and a Chihuahua from carrying mud into the house. Sixteen little paws were doing a number on their lawn and the grass refused to survive.

I had just finished laying a flagstone walkway for another woman and seemed to be on a rock and roll. I taught my grandson how to lay stone  on the last job and this time I was going to teach the handyman.

The first step was to lay out and measure the site so we could order materials. We needed one pallet of flagstone to cover 220 square feet, 3 tons of fine drainage gravel 4 inches deep, a 40 foot x 6 foot roll of heavy weed barrier cloth, 10 forty# bags of pea gravel to fill the joints, and one gallon of Gravel Lok to seal the gravel in place.

I suggested using the polymer to seal the joints so no loose pebbles would hurt bare feet or paws and no weeds will grow in the cracks.

Gravel Lok Joint Details

We went looking for the right pallet of rock at landscape nurseries and a brick and rock layers yard. I would have preferred 1 1/2 – 2 inch thick slabs but we ended up with 1+ inch pieces. The thicker pieces are stronger and handle weight better with less potential for cracking. With a good base they should be fine, especially since there  be no equipment driving over them.

Leveling the site using flat shovels and then tapering the grade away from the house was time consuming. We started with a level taped to a 2×4 and progressed to a line level on crisscrossing strings. This step is important to keep rainwater from flooding the basement.

Once we were satisfied with the grade we shoveled in 3 inches of the fine gravel. This provides drainage as well as a solid base for the flat rocks. We rented a gasoline powered tamper to settle it all in and prevent air pockets. The layer of landscape fabric was laid on top and held down with the last inch of gravel. A thunderstorm rolled in and the whole area got covered with 6 ml plastic, held down with rocks along the edges.

The slabs of rock had to be laid on edge in the yard so the size and shape of each one was visible. Look at the space, look at the rocks, look at the space, measure, pick the most suitable. One edge was straight, up against a raised concrete pad, so the straightest pieces went there. There were a good many big pieces with a nice curved edge and they went for the outside edges. Then we filled the middle, chipping off some difficult angles as needed. It is like putting together a giant jigsaw puzzle, except it takes two people to move each rock.

We leveled each rock (slightly down hill), dropping them on their cushion of fine gravel, picking them up to check for air pockets, resetting them…Adjusted each to lay flush with it’s neighbor, reset it…Stomped on them and tried to rock them. Reset them…It is tedious work down on your knees but satisfying when you finally get it right.

Once all the rocks were laid in, I vacuumed out the loose gravel between the stones so that the pea gravel would fill the entire gap between each one. Then I washed the pea gravel a bag at a time by swishing it around with water in the wheelbarrow and scooping it up with a plastic sieve and spreading it out on landscape fabric to drain and dry. It was hot in the afternoons so it dried fast.

Draining the Pea Gravel

The next step was to mix in the liquid GravelLok with the pea gravel in a plastic mortar pan and start troweling it in the joints. After the first batch I decided to lay painters tape on all the edges to keep the polymer from dripping on the rocks and then having to quickly wipe it off with Acetone. It was much cleaner and faster with the tape.

Painters Tape on Rock Edges

The gravel mixture was pressed in to each joint and it solidified quickly. You can sweep or blow off the patio and hose it off without worrying about dislodging the joint material, which is quite nice.

Finished Patio

I think the project turned out well and the dogs love it too.

-Wendy lee, writing at Edgewisewoods, Gardens and Critters