How to Build a Retaining Wall with Blocks

A retaining wall can redefine your landscape by allowing you to reclaim problematic slopes and create beautiful and functional terraced gardens. It’s easier than you might think to feel, level a patio area or create attractive planting beds when you know how to build a retaining wall with blocks. That said, constructing a retaining wall is an involved process that requires careful preparation and hard work. However, if you follow the steps below, you will find that the process is straightforward. Thus, this guide will provide simple steps on how to build a retaining wall with blocks:

Table of Contents

Before you start planning and preparation

The most critical stage of this project is proper planning. An anticipated plan can save time, avoid costly mistakes, and make sure the wall can solve the test of time.

Check local codes and utilities

Before you dig, you must make a critical call. You should dial 811 visit your local call before you dig service to have underground utility lines marked on your property. Hitting water, gas, or electrical lines can be deadly and expensive. In addition, please contact your local building department to see if a permit is required. Check with your building department to see whether a permit is required. Municipalities frequently require a permit for walls over a certain height, usually three to four feet. If your wall is taller, you will almost certainly need professional engineering to ensure that it is constructed and fortified.

Choose Your Site and Design

Walk your property and decide the best place for your wall. Consider the slope of the land, the finished product’s intent, and whether the wall will be straight or curved. Utilize stakes and string to outline the wall’s form, or lay it out in the garden using a garden hose. Consider the height of the wall. This factor will determine the type of block you require and whether you will need additional soil reinforcement. In general, most interlocking block producers recommend geogrid for blocks over three or four feet tall.

Gather Your Tools and Materials

Having everything on hand before you start makes the process much smoother. Here’s a list of what you’ll likely need:

Tools:

Shovel (round and flat)
Wheelbarrow
Tape measure
Stakes and string line
Level (a 4-foot level is ideal)
Rubber mallet
Hand tamper or plate compactor
Caulking gun for landscape adhesive
Chisel and hammer (for splitting blocks if needed)
Safety glasses and gloves

Materials:

Retaining wall blocks (calculate the quantity based on your wall’s dimensions)
Capstone blocks (for the top course)
Paver base or compactible gravel (for the foundation)
Coarse sand (for leveling)
Drainage stone (¾-inch clean gravel)
Perforated drain pipe and fabric sock
Backfill soil
Landscape adhesive

Building Your Retaining Wall Guide

You have the plan, and all materials prepared, now it is time to start building.

Step 1: Excavate the Trench

The foundation is the key to the structural integrity that is your wall. You need to dig a trench that the base material and course one of blocks in your wall sit in.

Trench Dimensions: The trench needs to be wide enough to fit a block and at least 6 inches of extra space, behind the block, for drainage stone. It should be deep enough to fit a 4- to 6-inch layer of compacted base material with half a block’s height left over. The buried block is the foundation of stability in your wall. It must be buried out of sight.
Digging: Using the stakes and string line as your guide, start digging. Remove all grass, roots, and the topsoil that accompanies them. Make sure the bottom of the trench is as close to level as you can get it. Use the shovel to clear out any remaining loose dirt.

Step 2: Prepare the Foundation Base

Without a level foundation, your wall will eventually shift or settle over time.

Add Base Material: Fill the trench with 4 to 6 inches of paver base or compactible gravel. Spread the base material throughout the length of the trench.
Compact the Base: This step is easy but essential. If this is a smaller project, use a hand tamper. For longer walls you might have to rent a plate compactor. Compacting the gravel in 2 to 3-inch layers ensures a strong, level base. Make sure it is level by working back and forth and from side to side. If it is adequately compacted, walking on it should not leave a footprint .
Leveling: To check level on both the front to back and side to side plains, use your 4-foot level. Add or remove base material as needed to make it perfect. For a final, perfect adjustment, add a thin layer: about 1 inch of coarse sand to the compacted gravel.

Step 3:Lay the First Course

The first course is the most important, and everything starts from it. Therefore, do not be in a hurry and try to make it as even as possible.

Placing the Blocks: After preparation, place the first block and put your level on it. Moreover, you should be sure that the element is positionated perfectly from front to back and from side to side.

Aligning the Course: Place the second block next to the first block so that they touch each other tightly. Repeat the procedure and always make sure that the level of both adjacent blocks is the same. Thus, you will connect the whole wall for the entire length and make all the necessary changes. When you put the first row of the block, follow the string line to do everything at the right height.

Backfill the Front: When the first row is ready, try to fill the trench in front of the blocks to fix their position.

Step 4: Drainage Installation

Proper drainage should be one of the priorities when it comes to a retaining wall. Failure of a wall occurs mainly due to water pressure, also known as the hydrostatic pressure.

Lay the drain pipe: Install a 4-inch perforated drain pipe under the first course of the blocks running across the wall’s length. Ensure that the perforations face downwards. Have the pipe be at a slight inclination to the bottom, approximately 1/8” per running foot to an open outlet at the wall’s end, where the water will flow away. The pipe should also have a fabric sock to prevent clogging with dirt. Add
drainage Stone: Fill behind the blocks with a minimum of 12-inch ¾-inch drainage stones. The stones will form a passage channel through which water will freely flow down to the drain pipe.

Step 5: Stack the Remaining Courses

When the base and drainage are done, lining the remainder of the blocks is pretty fast.

Stagger the Joints: Start the second course using a half box to achieve the staggering, running bond; the laid blocks should look like a brick wall. This arrangement helps spread the pressure and empower the wall. Most of the block formats come with half containers. Alternatively, you can purchase a chisel and hammer the block into half.
Set and Secure: Sweep any debris off the top of the previous course. Place the blocks, making sure to lock them into the course below them. Most modern blocks have a rear lip or a pin system that automatically creates the right setback. Settle the blocks firmly into the base with a rubber mallet.
Check for Level: Check that the course is level from front to back after every three or four blocks.
Backfill as You Go : Once every one or two courses, fill in the space behind the wall with more drainage stone. Also, add backfill soil behind the stone and compact it lightly. Do not compact with heavy machinery near the wall.

Step 6: Add Geogrid Reinforcement (If Needed)

For walls over 3-4 feet high, you will need to install geogrid.

Lay the Geogrid: Cut a piece of geogrid to the length specified by the engineer or block manufacturer (typically about 60-80% of the wall’s total height).
Position It: Lay the geogrid on top of a course of blocks, with the edge near the front of the blocks. Place the next course of blocks on top of it to lock it in place.
Stretch and Secure: Pull the geogrid taut behind the wall over the compacted backfill. Stake it down temporarily and cover it with more compacted backfill soil.

Step 7: Finish with the Capstones

This final course will give your wall a polished, professional appearance.

Surface preparation: Brush off the top of your last course of blocks, making sure it’s clean and dry.
Apply adhesive: Use a caulking gun to apply two generous beads of landscape adhesive to the top of the wall.
Set the caps: place the capstones firmly into place on the adhesive. You can sit them flush with the front of the wall, or you can have them overhanging slightly. Give them a gentle tap with a rubber mallet to hold them in place, and let the adhesive cure for at least 24 hours.

Final Words

Constructing a retaining wall with blocks is a considerable investment. The end product, on the other hand, becomes a strong, working, and appealing piece on your land. When you lay a strong foundation, appropriate drainage, and appropriate blocks. You will have a feature that will elevate your lawn. You may now put your hands on your waist and appreciate your masterpiece!