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Build a Block Retaining Wall

Materials List
Retaining Wall Blocks
Landscape Fabric
Gravel (optional)
Tools List (click item to shop)
3 lb. Drilling Hammer
Carpenter's Level
Mason's Line
Flat-Pointed Shovel
Hand Tamper
Safety Glasses
Back Support
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Building a Dry Stone Wall

IMPORTANT: Read this before you start


Do you want to level a steep slope on your property or enclose an area for a decorative garden? Building a concrete block retaining wall is easier than you may think.

The concrete blocks used in this project interlock and require no mortar for constructing a pleasant, stepped slope. Each block has a lip that locks it to the previous row. Aside from the weight, these blocks are as easy to assemble as children’s blocks. They are designed specifically to build relatively low walls up to 30” tall. For taller wall construction, you’ll need to prepare for drainage, reinforcement and stability.

Skill Level & Time To Complete
• Beginner -
• Intermediate -
• Advanced -

Helpful Tips
When calculating how many blocks you’ll need for your wall, remember that they are basically one foot long.

Curves require more blocks than straight runs.

When you have your blocks delivered, don’t have the pallets set on your driveway. The load is extremely heavy, and can cause damage.

1. Begin by measuring out your prospective wall, using stakes and mason’s line to mark off the key points. Or, you can use a garden hose to mark off the perimeter.
2. The key to a successful concrete block retaining wall is to start with a level foundation course of blocks. The foundation course must be below ground level so that the soil will hold it firmly in place. Starting at the lowest point, use a flat-pointed shovel to dig a trench. The dimensions of the trench will vary depending on the size of your block.
3. Tamp the trench with a hand tamper to compact the underlying soil.
4. If your property slopes, you may have to dig your foundation trench in a series of steps equal to the height of the blocks. Then, as you continue with construction, build up the lower sections with block until the stepped areas accept successive courses of blocks in a level wall.
5. Once you have a sound foundation trench, you can begin laying block, checking regularly for level. First pour a one inch layer of sand underneath the foundation course to provide a more solid base. The sand will make leveling easier and improves drainage.
6. Set the first block in place and tap it with the butt end of your drilling hammer if not level. If your property is relatively flat, continue laying the foundation course, making sure that all blocks are level with each other and below ground. If the ground slopes build up the lower sections with block.
7. Once the entire foundation course is installed, set one block in position at each end. The lip of each should fit against the back of the foundation course block. Check the level of the foundation course before you start the second course. If necessary, adjust the retaining wall blocks until the foundation course is completely level.
8. Cut one block in half for the start of the second course to ensure that the first and second courses are staggered. Set the rest of the second course blocks in place and then fill the trench around the foundation course with soil.
9. Continue placing blocks, making sure each course is staggered over the previous one.
10. To prevent the soil from seeping through the spaces between the blocks, line the cavity behind the wall with porous landscape fabric. Start at the base of the cavity and unroll the fabric until it overlaps the top course of block. Cut the fabric and continue along the length of the wall until the entire cavity is lined.
11. Backfill the cavity with soil. If the wall is 2 1/2' or higher, fill the area closest to the block with gravel. You should have gravel to a width of about 6" from the block. The rest of the cavity can be filled with soil. This will facilitate drainage.
12. Trim the excess landscape fabric. You can top off the terraces with decorative stone or mulch.
13. And there you have it…a decorative wall that will help define and accent your property. Your concrete block retaining wall is as aesthetically pleasing as it is useful.



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