Be sure you’re not going to dig through a utility line as you start your project. In the United States, call 811 to see which utility lines are on your property. Your local building codes may also specify how deep the footing needs to go. Typically, you need to make your footing twice as deep as the thickness of the wall.

To ensure you’re digging in a straight line, snap a chalk line onto the ground to create your base shape.

Make sure that the 2x4s are flush with the top of the hole that you dug. That way, the concrete won’t spill out of the top.

For a large retaining wall, consider renting or hiring a concrete mixing truck to come and pour the concrete for you.

Type M mortar is the strongest mortar mix out there, so it’s ideal for this project. Use a drill and a mortar mix drill bit to make this process easier. Try not to mix more mortar than you can use. Mortar dries out quickly, and any extra mortar you have will need to be thrown away. Wear protective glasses, gloves, a ventilated mask, and long jeans. [8] X Expert Source Gerber Ortiz-VegaMasonry Specialist & Founder, GO Masonry LLC Expert Interview. 10 March 2020.

You may notice that the mortar falls off your trowel quickly, which can be frustrating. To keep it contained, scoop mortar up with your trowel, then tap the flat side of the trowel onto a flat surface. The remaining mortar will be thin and stick to the trowel until you’re ready to apply it.

Use your string to make sure your corner block is level and in a straight line.

Apply mortar at the end of the block before you place the block adjacent to it.

Tap the blocks for any alignment adjustments while the mortar is still wet. Do not try to move a block after the concrete has set, since that could make your wall unstable.

Keep the mortar on the sides of the blocks so that it doesn’t fall into the hollow center. It won’t hurt your retaining wall, but it will just waste your mortar.

Use a level every 2 to 3 layers to ensure your wall is flat. If not, remove bricks from the uneven layer and try again.

For best results, move across each joint 2 times, and keep your tool wet. There are several different joints to choose from, but the concave joint is the easiest to do for beginners.

Mortar mix can take up to 28 days to reach its full cured strength.