Around the House: Build a Retaining Wall

Retaining walls are widely used by consumers and contractors alike in the quest to improve a particular landscape. They come in a variety of materials (brick, stone, rock, concrete, wood and steel) and colors, and are durable enough to fight the effects of weather, soil erosion and even insect invasion.

The following installation tips will help you transform useless land into a wonderful combination of colorful flowerbeds or green gardens. Retaining walls also give support to sloping land and can add the touch of beauty you might be looking for.

Step 1
Dig the trench as deep and wide as the manufacturer recommends, making note of recommendations regarding the frost line in your area. Use a mason’s line as a guide to make sure the wall is being built straight.

Step 2
Line the trench with landscape fabric. Unroll a piece of landscape fabric and lay it on the floor where you will build the simple wall. Allow enough to fold back over the trench area, plus an additional 3 inches, and cut to this length.

Step 3
Lay the first course of blocks. Cover the landscape fabric with 2 to 3 inches of gravel and tamp it. Lay the first course in line with the mason’s line. If the blocks are set lip-up, leveling them and laying later courses is easier. Check for level and add or remove gravel as necessary.

Step 4
Lay a second course of blocks with their lips pointing down over the back of the wall. Check again to make sure they are level and make any needed adjustments. Lay a third course of blocks the same way, leaving an exit point for a drainpipe at one end of the wall.

Step 5
Before starting to build corners and sidewalls, add gravel for the drainpipe behind the placed blocks. Slope the gravel 1 inch every 4 feet, checking with a 4-foot level set on a board with a 1-inch spacer under the downhill end.

Step 6
Lay the drainpipe on the gravel. Run the drainpipe to the point where it can exit the ground. Backfill with gravel behind the wall until the drainpipe is covered. Tamp the gravel firmly.

Step 7
Split the blocks for corners. For a 90-degree corner or the end of a straight run, you’ll need to cut blocks. Score a full block with a circular saw and a masonry blade, then split the block at the scored line by striking it with a brick chisel and 3-pound sledgehammer.

Step 8
Build the corners. Place the half blocks on alternate sides of the corner so they overlap. Chisel the lip off a block if it interferes with construction, then secure the block with a bead of construction adhesive.

Step 9
Alternate half and full blocks at the end of a straight run. Place the half block so the cut edge is on the outside end of the course. Continue building the wall, adding gravel and tamping after every few courses.

Step 10
A course or two below the top of the wall fold the landscape fabric back over the gravel and trim off any excess. To help secure the top course of blocks, apply construction adhesive using a caulking gun and lay the top course. Press down firmly on each block.

Step 11
Backfill with soil behind and front of the wall and tamp the soil firmly.

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