Give your plain landscape a stunning makeover with a block retaining wall.
Product costs, availability and item numbers may vary online or by market.
Missing anything? Shop Online
The blocks for this project have a locking flange — which makes the installation easy. The interlocking blocks can be used to build walls up to 28 inches high. Follow the block manufacturer's instructions concerning wall height limits.
Plan your layout. Avoid having downspouts pointed at the retaining wall and, if it's against the house, keep soil and mulch well below the siding.
Your retaining wall design will determine how you mark the area. To mark a freeform layout, use a rope or hose to outline the shape. Then use a shovel to mark the outline. For straight lines, mark the entire bed area with stakes, string and marking paint. Mark curved corners by tying a string to a stake that's equidistant to the edge — creating a compass — and spraying the curves with marking paint.
To determine how many blocks you'll need per row, divide the total length of the wall by the length of the block. To see how many rows you'll need, divide the ideal wall height by the height of the block — account for the first row to be half-buried. See Planning for a Block Retaining Wall for more information on estimating project materials.
Before you buy materials or begin work, check local building codes and your homeowner's association regulations to see if there are any restrictions or requirements you need to follow. A permit may be mandatory in some areas.
Blocks can be heavy — wear a back support if necessary. You may want to enlist a helper to share the work. Consider having the material delivered.
Purchase 10% more blocks than your estimate. The excess should account for breakage, cutting blocks and replacements for future repairs.
With the layout marked, you can begin digging the trench. To bury the first row about halfway, dig the trench about 4 to 6 inches deep and 12 inches wide, or twice the width of the block.
Before beginning any excavation, call 811 to check for underground utilities.
If the trench slopes, you'll have to step up or down to keep the blocks level. Use a torpedo level to create steps so that each section of the wall remains level. You do not want the wall to run parallel to the slope.
Tamp down the dirt with a hand tamper and keep it level.
Fill the trench with about 3 inches of paver base, spread it with a rake, and tamp it down. Tamping the base provides a strong foundation. When it's all level, you can begin installing the blocks.
Wet the paver base if it's dry and dusty.
For row one, knock off the flanges with a hammer and chisel so the blocks will sit flat.
Wear safety glasses and work gloves when using a chisel on the blocks.
Beginning at the end with the lowest elevation, set the first block in place and check for level side-to-side and front-to-back.
Place the next block, making sure it's even with the first. Continue installing the first row, periodically checking for level.
A 6- to 9-inch torpedo level is useful for checking level of individual blocks or checking level front to back. A longer carpenter's or mason's level — 24 inches and up — is good for checking level over several blocks.
To level the rows and keep the blocks even, fill in under low blocks with paver base or tap down high blocks with a rubber mallet.
After installing each row, sweep dirt off the tops.
To start the second row you’ll have to cut a block to stagger the joints. Mark it, and cut it with a masonry blade.
Wear safety glasses, hearing protection and a safety mask / respirator when cutting block. Follow the saw and blade manufacturers' instructions for use and safety.
Put the cut block in place, keeping the flange tight against the first row. Check it for level.
After installing the next few rows, you'll need to add drainage directly behind the blocks. Lay down landscape fabric behind the wall, leaving enough excess to reach the top of the blocks.
Fill in directly behind the wall with gravel, then continue to build, by adding more rows.
For the last two rows of full blocks, apply concrete adhesive to the wall block tops, then set the next row of blocks in place.
If you're adding block caps, apply adhesive to the top row of block before placing the caps.
Fold the excess fabric back and fill in with soil and plants.