How to Rebuild a Concrete Block Retaining Wall | Ask This Old House

Ask This Old House mason Mark McCullough rebuilds a retaining wall that was stacked with the wrong material.
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Time: 2-3 days
Cost: $4000
Skill Level: Moderate
Tools List for Rebuilding a Concrete Block Retaining Wall:
Shovels []
Wheelbarrow []
Tamper []
Rubber mallet []
Level []
Wet saw []
Shopping List:
Tarp []
Gravel []
Concrete blocks []
Channel connectors
Fabric liner []
Perforated plastic pipe []
Construction adhesive []
Steps:
1. Remove any plants lining the retaining wall with a shovel. Dig deep to give the plants a strong root ball.
2. Transfer plants temporarily to a tarp for safekeeping.
3. Remove the pieces of the old wall.
4. Dig a few inches back and deep along the location of the old wall.
5. Lay a thick base of gravel along the trench. Pack it down tight with a tamper.
6. Lay the first course of blocks about halfway deep in the trench. Lay one block every six feet or so along the length of the wall, level those to one another, and then fill in the rest of the wall. Use the rubber mallet to secure the blocks in place.
7. Lay a fabric liner along the back and base of the wall.
8. Backfill behind the first course with more gravel.
9. Lay the next course of blocks. Line up the channels using the channel connectors. Be sure to not overlap face joints.
10. Lay the perforated plastic pipe behind the wall and backfill with gravel.
11. Install the next course of blocks the same as the second. Backfill with gravel. Repeat until the wall is at the desired height. Some blocks may need to be cut with a wet saw to ensure an even fit on each course.
12. To secure the top cap for the blocks, add construction adhesive to the top course of blocks. Then add the cap pieces. Even it out with the rubber mallet.
13. Return any plants back to the wall if needed.
Resources:
Mark used Mini Creta 6” landscape blocks in the color sandlewood, manufactured by Techo Bloc (/).
To join the top cap to the blocks, he used Gorilla Construction Adhesive, manufactured by Gorilla Glue [] (/).
Everything else he used, including shovels, landscape fabric, and gravel can be found at home centers, landscape and masonry supply stores.
Expert assistance for this project was provided by MJM Masonry (/).
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How to Rebuild a Concrete Block Retaining Wall | Ask This Old House
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