Home Improvement Ideas Outdoor Structures Retaining Walls How to Build a Concrete Block Retaining Wall Add style and support to your yard with a concrete retaining wall. You can build one in just six steps. By Caitlin Sole Caitlin Sole Caitlin Sole is the senior home editor at BHG. She is a writer and editor with nearly a decade of interior design expertise. She has vast experience with digital media, including SEO, photo shoot production, video production, eCommerce content, print collaboration, and custom sales content. Learn about BHG's Editorial Process Updated on January 31, 2024 Trending Videos Close this video player Photo: Rob Cardillo Project Overview Total Time: 1 day, 6 hours Skill Level: Advanced Estimated Cost: $20 to $35 per sq. ft. Yield: Concrete block retaining wall Concrete block retaining walls are ideal for holding back the soil after digging into a slope for a pathway, patio, or landscaping project. Concrete block retaining walls are generally the same as freestanding block walls but with a few crucial differences. A retaining wall must provide a way to release the water that builds up in the slope behind it. Without a pressure-relief system, the weight of the water in the soil would crack or even buckle the wall. Weep holes, lengths of ¾-inch pipe inserted along the top of the first course, escort some of the water out. The other part of the system is a plastic drainpipe covered with gravel. As water accumulates behind the wall, it percolates through the gravel into the drainpipe, which carries it off safely. Concrete block retaining walls must be stronger than freestanding walls. Insert rebar in the footing when you pour it; this should be done every three blocks or at intervals specified by your local codes. As the last step, fill the cores around the rebar with mortar from the bottom to the top. Expect to spend 20-36 hours building a 3x10-foot concrete block retaining wall. Before you begin, you'll need to design the layout and pour the footing. Use This Slope Garden Plan to Add Color to a Hillside and Stop Erosion What You'll Need Equipment / Tools Measuring tape Brick set Small sledgehammer Chalkline Pencil Mason's trowel Level Mason's blocks Wheelbarrow Striking tool Story pole Shovel Materials Concrete blocks 2x4 stakes 2x8 lumber Mortar Gravel 4-inch perforated drainpipe Landscape fabric 3/4-inch pipe Instructions How to Build a Concrete Block Retaining Wall Abramowitz Creative Studios Build and Prep Footing Lay out the wall and excavate the slope and the footing trench. Build the footing and insert rebar into the wet concrete at intervals corresponding to the cores in the blocks. Prepare the footing, spread mortar, and build leads, sliding the block over the rebar as needed. How to Repair Brick or Block Walls—and Prevent More Damage Abramowitz Creative Studios Insert Weep Holes As you lay the second course of the concrete block retaining wall, insert weep holes (¾-inch pipe) into the mortar every third block. Chip off a small recess in the block and trowel a mortar bed for the pipe, sloping it slightly toward the front. Then, chip out a recess on the next block, butter the ears, and set the block. Abramowitz Creative Studios Scrape Off Excess Mortar Stop occasionally to check the mortar. When it begins to set up slightly, scrape off the excess with an upswing of the edge of the trowel. Do not plug the weep holes with excess mortar as you remove it. Abramowitz Creative Studios Lay Landscape Fabric After you've laid at least two courses, spread landscape fabric on the soil behind the base of the concrete block retaining wall, temporarily laying the excess over the grass on the slope. Lay rocks on the fabric to hold it while you work. Backfill the wall with gravel between the rear of the wall and the slope, laying perforated drainpipe on the gravel bed level with the top of the first course. Face the holes down. How to Use Landscape Fabric to Control Weeds Abramowitz Creative Studios Cover Drainpipe Shovel more gravel on top of the drainpipe. Backfill with additional gravel as you add courses to the wall. Fold the landscape fabric over the top of the gravel fill, and backfill with soil. Replace the sod. Abramowitz Creative Studios Fill with Mortar When you reach the finished height of the concrete-block retaining wall, fill those cores containing rebar to the top with mortar. Mix the fill mortar slightly wetter than what you'd use for joints. Smooth the top with a trowel. Spread additional mortar, and lay cap block to finish the wall. Landscaping Walls for Your Yard How to Build a Mortar-Free Wall with Interlocking Retaining Wall Blocks How to Build a Retaining Wall on a Slope How to Build a Landscape Wall and Keep it In Tip-Top Shape 11 Retaining Wall Ideas to Maximize Your Outdoor Space