Q: The stone walkway at the side and back of my home is several years past hazardous. The pavers are no longer flat, caused in part by elderly tree roots. At the side of my house, the pavers are sturdier, but they also need to be made secure. Drainage issues appear to contribute to the overall issue. I’m in need of a solution from a landscaper, and it needs to result in a pathway that’s safe.
A: You have a choice of solutions, ranging from a relatively inexpensive, do-it-yourself path that will probably require regular, ongoing maintenance to a considerably more expensive, professionally installed option that should just need simple upkeep, such as keeping the path free of slippery moss.
Whatever the solution, though, be sure to address the drainage issue and a safe way to navigate the change in elevation where your lot slopes. Your new path also needs to take the tree roots into account.
In one picture you sent, a gutter downspout ends about a foot above the soil. During a rainstorm, water is probably cascading out like a waterfall, making erosion even more likely than if the water flowed out at ground level. And the exposed tree roots and the mud splashed onto the brick of your house hint that quite a bit of water may be running down the slope.
At a minimum, you should connect the downspout and any other uphill downspouts to a pipe that empties the water downhill, beyond the path. But make sure your runoff doesn’t create a problem for a downhill neighbor.
If there is a lot of surface water, you might need a more complex drainage solution. Get advice from a couple of landscapers. It’s possible, though, that simply covering the exposed tree roots and the slope with up to eight inches of mulch — not soil — will reduce the erosion significantly. Adding soil would stress your tree or trees by blocking the oxygen needed by their fine roots near the surface, said Ruth Williams, a certified arborist for Davey Resource Group, which provides a variety of tree-related services nationwide. But mulch is porous enough to let oxygen through.
If your lot is steep, you might need to install something horizontally across the slope to keep the mulch from slipping, such as straw wattles, which look like thick snakes of straw wrapped in mesh. A 25-foot wattle that’s nine inches in diameter costs about $150 at home improvement stores.
In designing your new path, pay particular attention to including steps with a consistent height difference, so people don’t trip or stumble. For outdoor steps, there is a handy formula to ensure that they’re safe. The depth of the tread plus twice the riser height should equal 26 to 27 inches. It’s awkward to walk down a slope where steps rise by just the thickness of pavers. A rise of four inches, which implies treads 18 inches deep, is easier. Outdoor steps with a rise of 5.5 inches to seven inches are generally most comfortable. That range implies treads 15 to 12 inches deep.
Asked to suggest an option that homeowners could do themselves, Doug Del Gandio, owner of Four Seasons Landscaping in Damascus, Maryland, said that a general rule of thumb is “the easier the install, the more maintenance the walkway is going to be.”
If you want to rebuild the path on your own, the easiest solution would be to install a thick base of crushed gravel — after you fix the drainage issues. Add edging to keep the gravel in place. You could then set the pavers you already have on that, or go with gravel alone. As the pavers heave or settle over time, or as tree roots poke through the gravel, you would need to add gravel to keep the path level.
If you opt for a professional job, Del Gandio recommends installing a stone walkway over a concrete base, which would cost about $40 a square foot. This type of path would just need sweeping, hosing or power-washing to keep it free of leaves, moss and other debris.
Where tree roots are growing underneath a path, Williams recommends installing a gravel path or building a deck-style elevated wooden walkway supported by piers set into the ground. Steps would be easy to incorporate in an elevated walkway.
When a concrete path or a concrete base is built where tree roots are an issue, people sometimes cut the roots first as a way of preventing future damage. But that often doesn’t work, Williams said. Unless the tree dies, which is always a risk when roots are cut, it will send out new roots, generally in the same direction, she said.
Instead, if you’re sold on installing concrete, either alone or as a base for stone, Williams recommends adding crushed stone over the roots, as a base for the concrete. You can then add mulch to make the surface level. Or, where a path is fairly level, Williams recommends installing a product called TripStop at joints in the concrete. Made of extruded PVC plastic, TripStop acts as a hinge, keeping concrete sections aligned even as they are pushed up unevenly by roots from below.
Where mud is caked onto the brick, consider spreading pea gravel between the path and your house. Gravel breaks up the fall of raindrops and keeps mud from splashing up. Planting ground cover also works, but it takes time for the plants to fill in.