How to Build a Retaining Wall
Construct a durable gravity retaining wall by excavating a level trench, establishing a compacted gravel base, laying interlocking blocks, and setting up proper drainage.
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🧰 Required Tools & Equipment
- ✓ Shovel
- ✓ 4-foot spirit level
- ✓ Torpedo level
- ✓ Hand tamper
- ✓ Rubber deadblow mallet
- ✓ String line and stakes
- ✓ Caulk gun
📦 Materials & Supplies
- ✓ Interlocking retaining wall blocks
- ✓ Retaining wall capstones
- ✓ Crushed stone base material (road base)
- ✓ 3/4-inch angular drainage gravel
- ✓ Perforated drain pipe with sock
- ✓ Exterior concrete/landscape adhesive
⚠️ Safety Checkpoints & Warnings
- • Call local utility marking service (e.g., 811) before breaking ground to avoid buried power/gas lines.
- • Wear heavy-duty work gloves and steel-toe boots; lift heavy masonry blocks using legs, not back.
- • Wear safety glasses and a dust mask when sweeping stone dust or cutting/chiseling blocks.
📋 Step-by-Step Guide (6 Steps)
Mark and Excavate the Trench
Drive stakes and pull a taut string line along the planned front face of the wall. Dig a flat trench roughly twice the width of your blocks and deep enough to accommodate 4 to 6 inches of compacted gravel plus the depth of one fully buried block. Clear all loose organic topsoil and roots from the trench floor.
- • A straight, clean-edged trench running parallel to the taut string line.
- • Trench bottom is carved down into firm subsoil without loose leaves, roots, or pooling mud.
- • Digging too shallow and failing to bury the entire bottom course of blocks.
- • Excavating on a slope without stepping the trench vertically.
Install and Compact the Base Layer
Add 2 to 3 inches of crushed stone base material across the length of the trench. Pound the gravel thoroughly with the hand tamper until fully solid and unyielding underfoot. Add another layer until the base is 4 to 6 inches thick, checking continuously with the 4-foot level.
- • A flat, tightly packed gray aggregate surface along the entire trench length.
- • The 4-foot level shows the gravel pad is dead level in both directions.
- • Using rounded pea gravel or sand instead of angular crushed stone.
- • Failing to compact in thin lifts, resulting in settling later.
Set and Level the Base Course
Place the first retaining block at the lowest end of the trench, aligning the front face with your guide string. Use the torpedo level to check front-to-back and side-to-side level, tapping the block with the rubber mallet until true. Lay adjacent blocks tight against each other, leveling each one individually and across the whole row.
- • First row of blocks sits flush and aligned to the string line with tight joints.
- • Spirit level lays across three or more blocks simultaneously with the bubble centered.
- • Rushing the first course; any tilt or height variation will multiply with every higher tier.
- • Striking blocks with a steel hammer, chipping or cracking concrete faces.
Lay Perforated Pipe and Add Drainage Gravel
Place the perforated drainage pipe directly behind the first course of blocks with holes pointing downward, extending past the wall ends for daylight drainage. Backfill directly behind the blocks with 3/4-inch angular drainage gravel to a width of at least 8 to 12 inches. Tamp the backfill lightly to eliminate air voids.
- • Drain pipe lies nestled in clean angular rock behind the base course.
- • Gravel fills the void behind the blocks flush with the top of the first course.
- • Pointing pipe perforations upward, which prevents ground water from entering until water levels rise high.
- • Backfilling directly with native clay or topsoil instead of free-draining rock.
Stack Successive Block Courses
Sweep block tops clean of all gravel and debris before setting the next tier. Position the second course so vertical joints are staggered halfway over the blocks below (running bond pattern), engaging the rear locking lip or pins. Continue stacking courses, adding and tamping drainage gravel behind the wall after every single layer.
- • Vertical seams stagger symmetrically in a running bond brick pattern.
- • Wall exhibits a slight, uniform step-back (batter) toward the retained slope.
- • Aligning vertical joints directly on top of each other, creating weak fracture lines.
- • Letting grit stay on block surfaces, causing upper layers to teeter and wobble.
Secure Capstones with Adhesive
Dry-fit all capstones along the top of the final course to confirm spacing and overhang before applying glue. Lift each capstone, apply two thick zig-zag beads of landscape block adhesive to the underlying blocks, and press the cap firmly into position. Backfill the remaining gap behind the top course with native soil over a layer of filter fabric.
- • Capstones form an even, aligned coping layer with consistent front lip overhang.
- • Caps do not slide or rock when pressed by hand.
- • Applying adhesive on damp, frosty, or dirty block tops which prevents bonding.
- • Failing to dry-fit caps, resulting in an awkward small cut piece at the visible end.
Credit: inspired by an original tutorial by Home RenoVision DIY — watch the original on YouTube.
Don’t have everything?
- No Hand tamper? Heavy scrap 4x4 timber post used vertically to pound base flat
- No Rubber deadblow mallet? Standard hammer striking a scrap wood block placed over the stone