How to Repair a Retaining Wall

How to Repair a Retaining Wall

1. Mark the Repair Area

   Identify the damaged section of the retaining wall and mark its width on the top of the wall. Step back and look at the wall. The removed block will form a V-shape or inverted pyramid. Adjust the width of the markers so that the "V" will encompass the damage, plus another two blocks on each side.

2. Prepare the Site Below the Wall

   Lay plastic sheeting in front of the retaining wall to protect a lawn or sidewalk, as well as to catch debris.

3. Prepare the Block Storage Area

   Clear a flat, dry area behind the retaining wall for storing the removed wall blocks.

   Tip

   Clear a large area. For every 10 retaining wall blocks, clear an area of about 10 feet by 3 feet.

4. Remove the Cap Blocks

   Remove the cap blocks, if any, by knocking them off with a small sledge. Cap blocks are usually adhered to the retaining wall blocks with landscape block adhesive.

5. Remove the Blocks

   Remove the retaining wall blocks, starting at the top. Progress down in a V-shape. Remove all blocks down to ground level.

6. Store the Blocks

   Store the wall blocks in the storage area behind the wall. Keep the blocks in order.

7. Remove the Backfill

   Dig out the backfill material, if any. Clean backfill can be saved and reused.

   Tip

   Do not reuse sand, pea gravel, dirt, or any other inadequate backfill. Reuse only clean 3/4-inch angular rock or similar.

8. Fix the Cause of the Wall Failure

   Fix the condition that caused the retaining wall to fail. If the wall base is unstable, it should be dug out and refilled with gravel and crushed stone. Tree and plant root growth may need to be cut back. Incorrect masonry products like cinderblocks should be replaced with retaining wall blocks.

9. Clean the Remaining Blocks

   Clean off the tops of the wall's remaining blocks with the broom or shop vacuum.

10. Rebuild the Wall Base

    If the wall base is inadequate, dig it down to 10 inches. Add 8 inches of drainage stone, followed by 2 inches of crushed stone.

11. Add the Blocks

    Rebuild the retaining wall. Level each block from front to back and from side to side. Level each completed course, too.

    Tip

    If using any new blocks, scrape off bumps left from manufacturing by sliding one block over the other. Be sure to preserve integrated lips and grooves meant for locking the stones.

12. Backfill With Each Course of Blocks

    Pour backfill behind the retaining wall after each course of blocks is complete. A 12-inch-width is the required amount of backfill for most retaining walls.

13. Tamp the Backfill

    Tamp each new level of backfill with the tamping tool. Tamp lightly to avoid disturbing the wall.

14. Cap the Wall (Optional)

    Add retaining wall cap stones to the top course of blocks if needed to match the rest of the wall. Apply several generous beads of landscape block adhesive to the top course of wall blocks. Next, rest the cap stones on top, staggering them over seams.

Tips for Repairing a Retaining Wall

• Keep the retaining wall blocks clean on top and on bottom for a better fit.
• Add 4-inch perforated drain tube to the base of the backfill for improved drainage.
• Replacement retaining wall blocks can be difficult to match, even when the sizes appear to be the same. Take a block with you when shopping for replacements.
• Keep a V-shape or inverted pyramid in mind—not a square or rectangle—when calculating the number of blocks to remove from the wall.

When to Call a Professional

Call a landscaping company to repair retaining walls higher than 4 feet. Make sure that the company has experience with installing and repairing hardscaping materials.