How to Build a Retaining Wall
Construct a durable concrete block retaining wall with a level gravel foundation, embedded base course, integrated drainage pipe, and securely glued capstones.
- Read the tools, materials, safety notes, and steps below for free.
- Tap Start Camera Coach when you want hands-free voice help.
- Allow camera and microphone. Point your phone at the work; the coach watches your progress and tells you the next step.
🧰 Required Tools & Equipment
- ✓ Shovel
- ✓ Torpedo level
- ✓ 4-foot level
- ✓ Hand tamper
- ✓ Rubber mallet
- ✓ Caulk gun
- ✓ Wheelbarrow
📦 Materials & Supplies
- ✓ Interlocking retaining wall blocks
- ✓ Crushed leveling gravel (paver base)
- ✓ Drainage aggregate (crushed 3/4-inch angular stone)
- ✓ Perforated 4-inch drain pipe
- ✓ Non-woven landscape filter fabric
- ✓ Concrete retaining wall adhesive
- ✓ Retaining wall cap stones
⚠️ Safety Checkpoints & Warnings
- • Call 811 or local utility locator before digging to ensure no buried lines cross the trench path.
- • Wear steel-toe boots and leather work gloves to prevent crush and pinch injuries from dense concrete units.
- • Maintain proper lifting form by bending at the knees and keeping blocks close to your center of gravity.
📋 Step-by-Step Guide (6 Steps)
Excavate the Base Trench
Dig a trench along your marked layout line roughly twice the width of a wall block. Make the depth equal to 4 to 6 inches for the gravel base plus an additional 1 to 2 inches to bury the bottom portion of the base block course. Clear out all loose soil and square off the bottom.
- • A flat-bottomed, straight-sided trench clear of loose dirt and roots.
- • Trench depth uniformly matches the target base depth along the entire layout line.
- • Digging too shallow and leaving the base course resting above finished ground level.
- • Creating a V-shaped trench instead of flat, horizontal bottom.
Add and Compact the Gravel Base
Pour crushed paver base into the trench in 2-inch layers. Moisten the gravel lightly with water and pound it repeatedly with the hand tamper until fully solid. Check the compacted surface with a 4-foot level in all directions before adding subsequent layers up to a 4-6 inch total depth.
- • Tightly packed, grey gravel bed across the full trench width.
- • Level bubble perfectly centered when 4-foot level is placed along and across the base.
- • Pouring 6 inches of gravel at once without compacting in progressive thin lifts.
- • Compacting dry gravel, which fails to bind properly.
Lay and Level the Base Course
Place the first block at the lowest end of the trench. Use a torpedo level to check that the block is level front-to-back and side-to-side, tapping high corners with a rubber mallet. Set adjacent blocks tightly edge-to-edge, checking level across multiple blocks with the 4-foot level.
- • Base course of blocks aligned tightly end-to-end with no gaps.
- • Level vial bubbles dead-center both along individual blocks and across multiple block tops.
- • Accepting a 'close enough' slightly tilted block on the base layer.
- • Leaving sand or gravel grit on top of blocks before checking level.
Install Landscape Fabric and Drain Pipe
Drape non-woven landscape filter fabric across the back of the base course, extending it up the excavated dirt embankment with excess fabric draped over the top. Place a 4-inch perforated drain pipe directly behind the base blocks with the holes facing downward. Pour angular crushed gravel directly over the pipe.
- • Black or grey fabric lining the soil wall behind the blocks.
- • Perforated pipe resting flat at the base behind the wall, surrounded by clean angular stone.
- • Placing the drain pipe holes pointing upward, preventing ground water from entering low.
- • Omitting filter fabric, causing backfilled soil to clog the drainage rock over time.
Stack Consecutive Courses with Offset Seams
Sweep the top surface of the lower course completely clean of dirt and debris. Place the next course of blocks so that vertical joints are offset (staggered like running bond brickwork) from the layer below. Backfill the space behind the blocks with crushed drainage stone after each course is placed.
- • Vertical seams centered over the middle of the blocks directly underneath.
- • Clean aggregate gravel filled flush behind each newly laid course.
- • Aligning vertical seams directly on top of one another, which compromises structural strength.
- • Backfilling with clay or native soil instead of free-draining angular stone.
Adhere Cap Stones and Complete Backfill
Fold the top flap of landscape fabric forward over the top of the gravel backfill layer. Sweep the top row of wall blocks clean and apply two thick beads of concrete adhesive. Set the cap stones firmly into the glue, align their overhang evenly along the front edge, and cover the folded fabric with native topsoil.
- • Uniform cap stone overhang along the entire top edge of the wall.
- • Fabric completely enclosing the gravel drainage column beneath a layer of topsoil.
- • Applying adhesive on dirty, dusty block tops, which prevents bonding.
- • Letting cap stones set out of alignment before the adhesive cures.
Credit: inspired by an original tutorial by Lowe's Home Improvement — watch the original on YouTube.
Don’t have everything?
- No Hand tamper? Flat scrap 4x4 timber post end weighted with downforce
- No Rubber mallet? Standard claw hammer striking against a scrap block of wood