How to Repair a Retaining Wall

Retaining walls hold back immense pressure on slopes. Waterlogged soil, an unstable wall base, or poor backfill can further cause retaining walls to bow, lean, or blow out. Repairing a retaining wall is simple, though labor-intensive. As long as the blocks are in good condition, they can be reused.

When to Repair a Retaining Wall

Repair a retaining wall when the ground is dry and well-drained. If possible, wait until spring or summer to repair the wall.

Permits and Codes

If the retaining wall is above a certain height, a building permit may be required. Depending on your community, the height may range from 3 feet to 5 feet. Always check with your local building and permitting department.

Safety Considerations

Be careful when handling the retaining wall blocks. Larger blocks weigh about 60 pounds, with some blocks as heavy as 80 pounds. Wear eye protection.

Equipment / Tools

Bubble level
Shovel
Caulking gun
Tamping tool
Wheelbarrow
Broom
Shop vacuum
Sledgehammer
Eye protection

Materials

3/4-inch clear drainage rock
Fine crushed stone
Concrete retaining wall blocks (if needed)
Concrete wall cap stone (if needed)
Masonry block adhesive
6-mil plastic sheeting

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.
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.
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.
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.
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.
Store the Blocks

Store the wall blocks in the storage area behind the wall. Keep the blocks in order.
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.
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.
Clean the Remaining Blocks

Clean off the tops of the wall’s remaining blocks with the broom or shop vacuum.
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.
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.
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.
Tamp the Backfill

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

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