There are many ways to create permeable paths. You can use:
- manufactured permeable pavers,
- gravel, or
- plantable grid systems.
The first requirement is that path materials be permeable to air and water.Joints cannot be mortared, and you will need to limit soil compaction beneath the path to allow water to drain.
The other factor to consider is how the pathway will be used. How finished do you want the path to be? How flat? How accessible?
Gravel paths, at approximately $3 per square foot*, are on the inexpensive side. A gravel path is fairly simple to install. Any type of gravel will work, as long as it is not too small.
I would recommend gravel that is between 1/4 inch and 3 inches in size to ensure good water flow. It is important to prevent the gravel from mixing with the soil beneath it, or it will eventually become muddy.
You will want to install landscape fabric-also known as weed barrier-below the gravel. Landscape fabric is available at any big box store or retail nursery. You will also want some form of gravel retention (edging, bricks, railroad ties, etc.) on the sides of the path.
In the middle range of expense, you have permeable concrete pavers and turf-protection grid systems.Permeable concrete paving systems cost about $5 per square foot.
They are more complex than a gravel path to install, but simpler than working with raw stone. The permeable pavers interlock without mortar, and the concrete is mixed with aggregate to give the pavers a stone-like façade.
Turf-protection grid systems like EcoGrid supply a firm path base while allowing plants to grow on top of or through the structure. These systems can range from $3 to $6 per square foot in material cost, depending on the system and the plants you choose.
You could plant grass, sedums, delosperma, creeping thyme, even pachysandra and vinca. Stepping stones can be added to reduce stress on plants growing through the grid.
Grid systems are on par with concrete pavers in terms of installation complexity. (Depending on the project, they may be a little simpler to install.)
Slate and other types of stone
On the high end, costing $10 to $20 per square foot for materials, there are paths made with slate and other types of stone. You can use any hard, flat stone available, from granite to bluestone.
It's important that you don't mortar the joints, as mortar will obviously prevent water flow. It's also important not to let the path's base become compacted-an overly compacted base won't allow water to pass through. A 3/8-inch gravel base will have more air space and allow more water movement.
Paths made of real stone with a permeable base can be fairly complex to install.
Before you make a decision, be sure to research all aspects of installation, from cutting the stone, to choosing a firm (but still permeable) base, to maintaining the path over the long term.
* Price estimates in this article do not include labor costs.
For more information:
Read architect Polly Osborne's Q&A "We want to replace our small concrete patio with an inexpensive green material. Suggestions?"