A retaining wall holds back earth. While this goal is significant, it should not be the only design consideration. More important, a retaining wall must be designed to allow a passage for water to drain away from the wall. We strongly suggest you hire a professional engineer or landscape contractor specializing in retaining walls to design and build a reliable wall more than 3 feet high.
Any number of retaining wall design options may be just what your landscape needs. For instance, a stone retaining wall that cuts into a slope frees space unsuitable for a patio or walkway. A wall that cuts into a level lawn and forms a sunken garden room creates a microclimate that extends the growing season. Or a series of low terraces can be used to create level playing fields in a once-sloped backyard.
As a major focal point in the landscape, a retaining wall should be attractive and suit the setting. Keep in mind that the overall size of the completed wall will affect the impact of its presence. A series of low terraces will work in much the same way as one massive retaining wall to tame a slope but will look completely different.
A wide range of stone works well for retaining walls, from hefty boulders holding back a hillside to distinctive stone veneer mortared to reliable concrete block. If you're interested in the look of stone but not its price, consider the options available with stone-look interlocking concrete blocks. Learn more about shopping for landscape stone here.
Retaining walls also can be constructed out of wood. Wood does not offer the longevity that stone does, but its unique texture is appealing to some homeowners. Learn more about building a wood retaining wall here.
Never underestimate the engineering required to build a retaining wall. The lay of the lands and soil type have heavy bearing on a wall and must be considered. Building a low retaining wall to form a raised planting bed at the foot of a gentle slope is much different than building a 4-foot-wall to hold back the cut left after excavating a driveway through a steep hill. You'll need professional advice and assistance, as well as a building permit, to build a retaining wall higher than 3 feet. A low wall can be accomplished by most do-it-yourselfers.
Any retaining wall includes a varied selection of stone sizes, with the most substantial ones at the base and smaller stones filling in behind the wall's face. A dry-stacked retaining wall must be built so each course, or horizontal layer of stone, staggers backward into the slope. Staggering adds strength and will keep the wall from bowing or collapsing. The bank behind the wall should be cut away to angle back—bottom to top—minimizing any pressure it might place on the wall. Perforated drainpipe, laid in gravel behind the wall's base, will help carry water away. For stability, each course of the wall will be set back slightly so the wall angles back at least 6 inches for a 3-foot-high wall.