One particular backyard we had the privilege of renovating featured a flagstone patio and fire pit extending out from the basement door. The patio was set in a wooded backyard with a seasonal stream just beyond the patio. The problem with this backyard however, was that the patio was the lowest point; it had no ability to drain and the result was perpetual soft ground and constant heaving of the flagstones. Having been asked to “fix it”, our solution involved the installation of two French drains on both sides of the patio that would then drain into the seasonal stream. Since the walk-out basement door was a fixed point of the patio, we couldn’t simply raise the elevation of the patio.
Hence, the French drains allowed us to keep the existing grade, but still drain the water out of the area. Having completed the French drains, we rebuilt the flagstone patio with a deeper rock base ensuring it was built on a layer of geotechnical fabric. This allowed the load to be spread more evenly over the softer subsoils, preventing them from protruding into the clean rock base and compromising its’ load-bearing ability. Geotechnical fabric is a component that is often overlooked in base construction. It may not seem like a big differentiator, but the difference can often be noticed within 12 months of an installation. We are happy to say that the installation has maintained its’ integrity for over three years and should continue to offer a functional backyard space for years to come!