Q: I just purchased a lovely 1927 home in the hills above East Oakland, Calif. The previous owner didn’t want to have anything to do with anything green outside, so she had two concrete patios built in the backyard — one even with the lower level of the house, which I will keep, and the second one, consisting of individual concrete slabs, a few steps below that, extending to the property line.
I would love to have a real garden back there, not just containers, and have had various suggestions from friends and contractors about how to make the lower patio into a garden. Because the backyard is on a slope, it’s been suggested that the lower patio is probably helping prevent erosion and that I may want to keep the concrete in place and build raised beds on it.
Does this sound reasonable, and if so, would it also make sense to break one of the slabs up a bit if I want to plant a tree or two? Or, should I try to find someone to break up and haul away all that concrete and start with bare dirt in the lower part of the yard?
A: We say keep the concrete and let your imagination be your guide. To us, the gray concrete is a blank canvas on which to paint a dream landscape. Keeping the patio makes sense from a soil erosion standpoint. It also provides some hardscape that you can transform into an outdoor living area.
Raised beds made of brick, wood or more concrete will work. If you opt for this, understand that you must provide plenty of drainage, either by drilling holes in the concrete within the perimeter of the beds or by providing holes in the sides of the beds. In either case it might be a challenge to get the beds to percolate. Water must be able to leave the beds to avoid drowning the roots of the plants.
Considering this, we would go down instead of up by designing a number of planting areas in the patio to allow for shrubs and ornamental trees. This solution has a couple of advantages. It uses the existing concrete in a new way. Also, it avoids the labor and expense of jackhammering the entire slab and hauling it away. Trust us when we say that will be expensive. Dump fees these days are figured by weight, not volume.
But the most important plus is you’ll be free to create a unique design.
Cutting out the planting beds is a do-it-yourself project. Rent a concrete saw and an electric jackhammer to do the heavy work. Depending on how much you want to sweat you can substitute a sledgehammer for the jackhammer. Use a 3-pound "single jack" hammer and cold chisel to dress the corners.
A concrete saw is basically a motorized diamond blade on wheels and is available at tool rental shops. A hose is connected to the saw to spray water on the blade, which keeps it cool during the cut. They’re relatively easy to operate and the rental shop can give you instructions. Make sure to follow safety precautions. Cutting concrete is dusty, noisy work so a mask, safety goggles and earplugs will be part of your wardrobe.
Begin by marking the concrete for the cuts. You’ll need a carpenter’s crayon and a chalk line. Snap the chalk line on the concrete. Once you get the designs laid out, mark the lines with the crayon. The crayon won’t disappear during the cutting process.
You’ll be restricted to straight lines with the saw. But, if you want, you can add curves later by forming them with bender board and pouring a little fresh concrete.
Break out the interior of the cut with the jackhammer or the sledge. Remove the pieces to expose the underlying soil. Remove the corners of the cuts with the single jack and cold chisel.
So, what to do with the concrete shards left over? Consider using them to build up the edges of the planters. Either lay them on edge buried in the soil on the perimeter of the cut or mortar them together to create a rustic design. If you don’t like the monotone concrete gray, staining the patio is also an option.
The final step is to amend the soil for planting. The local nursery can guide you through this process, as well as suggest plants for your garden.
In any case, let your imagination be your guide. Create a Zen-like sitting area with dwarf bamboo and flowering shrubs, or an edible herb garden, or both. The choice is yours.