How to Build a Retaining Wall: Step-by-Step Guide for Landscape Blocks

Retaining walls tame slopes, prevent erosion, and create level planting areas. Dry-stack walls using interlocking concrete blocks are DIY-friendly and require no mortar, but are limited to about 3 feet high. Taller walls need engineering and mortar.

Preparation

Plan the wall's base width at half the wall height (e.g., 18-inch base for a 3-foot wall). Call 811 to mark utilities. Calculate materials: blocks, base gravel, sand, drain pipe, fabric, and adhesive. Have heavy materials delivered on a pallet to save labor.

Tools and Materials

• 2x4 (8 ft), 4-ft level
• Stakes, twine, batter boards
• Trenching spade, round-point shovel
• Rebar, torpedo level
• Construction adhesive
• Perforated drain pipe
• Hand tamper, rubber mallet

Installation

Excavate Trench

Mark layout with twine and batter boards. Dig a trench to manufacturer's depth (typically 6 inches). Add 1-2 inches of sand, tamp, and level. Lay landscape fabric along back and bottom, cover with gravel, and tamp.

First Course

Set the first block on the sand base, level side-to-side and front-to-back. Adjust with sand or mallet. Continue the course, checking alignment with a level across adjacent blocks. End with a full block—extend the trench slightly if needed.

Second Course

Verify the first course is perfectly level. Stagger joints by starting with a half-block if the first course ended with a full one. Place blocks with lips hanging over the previous course. Check level; shim with folded fabric or shingle pieces if needed.

Third Course

Continue staggering joints. At one end, leave a gap for a perforated drain pipe. Backfill behind the wall with gravel, lay the pipe (with fabric sock), cover with gravel, and fold fabric over.

Fourth Course & Capstones

Complete the wall to desired height (usually 3 feet). Backfill and tamp. Apply exterior-grade adhesive in a zigzag pattern and set capstones to cover gaps. Backfill behind the wall with excavated soil, tamp, and rake smooth.