Build a Retaining Wall

Gravity is patient. A retaining wall that looks solid in June can be leaning by October if the ground beneath it settles or water builds up behind it. The wall itself is the easy part — stacking blocks is satisfying, visible work. The real craft is in what you do before the first block goes down: excavating a level trench, laying crushed stone, and planning for drainage. A well-built retaining wall should look like it's been there forever, holding the slope without strain. Most residential retaining walls use concrete blocks designed to interlock and step back slightly with each course. The key is thinking like water. Rain will find its way behind your wall, so you need gravel backfill and perforated pipe to move it away before it builds pressure. Get the base right, keep courses level, and give water a path out. The wall will hold for decades.

1. Mark and Excavate Clean. Stake out the wall location and stretch a string line to mark the front face. Excavate a trench 6 inches deep and 12 inches wider than your block depth. The trench must be level side to side, but can step down with the slope front to back. Remove all organic material and roots.
2. Build a Solid Base. Fill the trench with 6 inches of crushed stone or ¾-inch gravel. Compact it thoroughly with a hand tamper or plate compactor, working in 2-inch layers. Check for level across the width — this base determines whether your entire wall will be straight. The stone should be firm enough that your boot heel barely leaves a mark.
3. Set Perfect First Course. Place the first row of blocks on the compacted base, checking level in both directions with every block. Use a rubber mallet to tap blocks down into the gravel until level. This course determines everything above it, so take your time. Brush off any debris before setting the next block — even a pebble throws off alignment.
4. Offset Every Joint. Add subsequent courses, offsetting vertical joints like a brick pattern — each block should span the joint below. Most retaining wall blocks have a lip or setback feature that creates a backward lean as you stack. Sweep each course clean before setting the next. Check level every two courses and make minor adjustments by adding or removing base gravel behind blocks.
5. Channel Water Away. Once you reach final height, place perforated drain pipe along the base of the wall, with holes facing down. The pipe should slope to drain at the wall ends or through weep holes. Backfill behind the wall with crushed gravel, not soil, for at least 12 inches. This gravel layer is your drainage zone — it lets water flow down to the pipe instead of building pressure on the wall.
6. Cap and Compact. Install capstones on the top course using construction adhesive to bond them permanently. Let adhesive cure per manufacturer instructions. Once caps are set, backfill the remaining space behind the gravel zone with excavated soil, sloping it away from the wall. Compact soil lightly to prevent settling.
7. Stabilize and Plant. Cover the soil behind the wall with landscape fabric to prevent erosion, then add topsoil or mulch. Grade the area behind the wall so water flows away from the top of the wall, not toward it. Plant ground cover or install sod to stabilize the slope within a few weeks.