How to Build a Retaining Wall Along a Sidewalk

Mark out the intended location for your wall with wooden stakes and string to guide you during construction.

Dig a trench along the guideline 4 inches deep and 1/2 inch wider than the width of the concrete blocks you have chosen. Position the trench 1/2 to 1 inch back from the sidewalk so that your digging does not interfere with the sidewalk pavers.

Tamp down the soil in the trench with a hand tamper, using a level to make the soil as flat and even as possible; the support must be flat in order for the wall to be level; otherwise the wall may lean toward or away from the sidewalk, threatening its structural integrity.

Add a 2-inch layer of leveling sand to the trench and tamp this down, checking levelness as you go; the sand allows excess rainwater to run out from under the wall and supplies a secure but soft base for the blocks.

Set your first block in place at one end of the trench. Face the tongue of the block upwards to connect with the next row of blocks. Submerge the block halfway under the soil line and down into the trench; depending on the size of your blocks, it may be fully submerged.

Set a level on top of the first block to ensure it sits flat. Tap its high point down with the back of your hammer or a rubber mallet until it sits flat, if necessary.

Lay the next stone immediately abutting the first and check it with a level. Continue to lay this first row of stones in the trench and ensure that each stone is completely level.

Measure to the center of the first block for the second row and draw a line around the center of the block. Score this line with a brick chisel and hammer all the way around the surface of the block. Position the chisel perpendicular to the scored line and firmly strike the back of the chisel to cut the block in half.

Set the first half-block of the second row so that the tongue and groove lines up with the joint on the block below. Cutting the block first ensures that the joints are staggered for better hold. Check the level as you install each brick in the second row, until it is complete. Continue adding blocks in rows, staggering alternate rows, as necessary to achieve the desired height.

Line the cavity and the back of the wall with landscape fabric. Fill in the area with gravel, as far back as 6 inches from the back of the wall if possible to assist with drainage and provide support for the wall.

Fill in the back of the wall above the layer of gravel with regular soil or decorative mulch.