If your garden has a hillside or slope, chances are you’ve had some challenges with it. Maybe the space is difficult to mow, or perhaps the soil just washes away with the rain. Rather than thinking of that slope as a problem, look at it as an opportunity! With a little bit of work, you can build a hillside terrace or retaining wall that can transform that troublesome slope into unique and attractive garden possibilities. Even establishing a few flat gardening levels or steps on a gentle slope will provide access and visual interest – and may even help reduce excess runoff that causes erosion. (That said, if you’re dealing with a very steep incline, unstable soil, drainage problems or uneven terrain, consult an engineer before attempting any renovation. Permits might also be required. Always check and comply with local codes.)
Turn that steep slope into a garden showcase by terracing and planting it with trailing beauties and clusters of tall bulbs.
Photo Credit: ©2001 Dolezal Publishing/Robert Dolezal
The steepness of your slope will really determine what kind of hillside terracing or retaining wall structures you’ll need. If you have a gentle slope, installing a low terrace or short retaining wall can be a great do-it-yourself project.
Although you shouldn’t buy any materials until after you determine the number, height and width of your terraces, begin by thinking about what kind of material you’d like to use for your project. It’s a good idea to stick with material that matches your garden theme. If you’ve got a natural theme, for example, go with natural materials like stone or wood.
Next determine where exactly your hillside terraces should go and how many you’ll need. (Generally, the steeper the slope, the more terraces you’ll need.) Measure changes in elevation on your site by driving a short stake at the highest point of the slope and a tall stake at its lowest point. Attach string flush with the ground to the short stake, pull it down the slope, and attach it to the tall stake. Use a line level on the string to make its attachment point even with that of the short stake. The vertical length of the tall stake, from its intersection with the ground to the point where the string is tied, is the rise – the change in elevation over the slope. The horizontal length of the string – from the short to the tall stake – is the run. A series of such measurements may be necessary on long or steep sites.
To fit your terraces to the slope, decide the height of each terrace. Then divide that height into the total rise to find the number of terraces you’ll need to install. Alternatively, divide the number of terraces you want into the rise to determine the height of each terrace. Either way, the distance between terraces is found by dividing their number into the run. (You can always make adjustments as you construct the project.)
Once you know what kind of material you’d like to use and have your measurements, consult with your local home improvement store or garden center to determine the amount of material, sand and aggregate you’ll need to finish your project. Then before you begin construction, clear the site of turfgrass and other vegetation. You’re now ready to build.
The following step-by-step guideline illustrates the construction of a dry-stacked stone island terrace built from fieldstone on a flat site. A similar approach can be used for a hillside terrace. So gather a line level, shovel, stakes, string and tamping tool, and follow the basic steps shown in the pictures and described in their captions. Once your terraces are installed, you can backfill them with rich soil and plant them up into a showcase of beauty that you can enjoy – from the ground up.
Installing Terrace
Installing Terrace - Step 1
Mark your hillside terrace’s location with stakes. Fasten a string between stakes to mark the final height, then verify the string is level. Excavate a trench 8-12 inches deep along the run of the terrace using a trenching shovel. Reserve the excavated soil as backfill for your finished terrace.
Photo Credit: ©2001 Dolezal Publishing/John M. Rickard
Installing Terrace - Step 2
Compact the base soil of the trench using a tamping tool until the base is firm. Add a 4-6 inch layer of sand to the trench bottom. (Sand helps you precisely level the first course of stones of the terrace.)
Photo Credit: ©2001 Dolezal Publishing/John M. Rickard
Installing Terrace - Step 3
Set and level the first course of stones, using a carpenter’s liquid level for accuracy.
Photo Credit: ©2001 Dolezal Publishing/John M. Rickard
Installing Terrace - Step 4
Stack additional courses of fieldstone one-over-two, covering all joint spaces and stepping back each course 1-2 inches from the face. (It’s easier to set and precisely level two end stones, then fill the space between them to the level, than it is to work from one end to the other.)
Photo Credit: ©2001 Dolezal Publishing/John M. Rickard
Installing Terrace - Step 5
Add aggregate immediately behind the finished terrace to stabilize it and provide a path for water to drain. Fill the rest of the terrace with topsoil mixed with excavated soil from the trench. Add more topsoil before planting, as your hillside terrace will settle and compact for several weeks after being filled.
Photo Credit: ©2001 Dolezal Publishing/Robert Dolezal
