Knowing how to construct a DIY retaining wall from scratch will save you important resources that you have to spend for an outside contractor. This tutorial will teach you how to build a tiered block DIY retaining wall. The height of each level is under one foot. This tutorial will allow you to practice these important steps on an easy slope, and increase your knowledge should you decide you want to tackle a higher retaining wall in the future.
Short retaining walls are ideal for the enthusiastic DIYer. With a low wall, you can avoid the common pitfalls of water drainage concerns, bulging, or collapsing walls.
DIY Retaining Wall Step-by-Step
We will consider the materials and knowledge you need for how to build a retaining wall with blocks. The general principles in this guide will work for retaining walls using other materials like bricks, natural stone, and railroad ties.
Before You Start Your Wall
- Permits – Before you gather the first tool or dig a trench, you need to check with the code enforcement in your area. Retaining walls impact other people in your area. There are often permits that you need to get regarding your plans. There will also be rules you need to follow before they will allow you to build a retaining wall.
- Utilities – Check with your utility companies to make sure that you will now dig or build over important lines that provide your home with services.
- Neighbors -It is best to talk with them to let them know your plans if building a retaining wall impacts your neighbor in a direct way. This is true even if building permits are not required for your retaining wall.
- Landscape – Consider the landscape of the area where you want to build the wall. Does it lend itself to a particular wall design or height?
- Foundation – You need to think about the type of soil that is in the area you want to build your wall. Light granular soils are the best because they allow for drainage. Organic and clay soils are heavier and retain water. You will need to replace the soil if it is too wet or soft to support a heavy structure like a wall.
Retaining Wall Planning
- Get a piece of grid paper and a pencil and sketch out the area where you are building the wall. Take note of any large immovable objects like trees or air conditioning units that you need to account for in your design.
- Measure the slope of your area and mark this on your paper plan. Begin at the lowest point and mark the grade changes in one foot increments up the slope.
- With the slope calculations determined, decide how many tiers you want to create as you build your block retaining wall. The number of tiers will determine the height of each level according to the slope.
- Decide on the cut and fill site for each tier. The cut site is where you cut into the ground and remove the soil you need to construct each level. The fill site is where you will need to fill behind each section to create the level ground behind the wall.
- Estimate and order the correct amount of retaining wall blocks for your project. Use this tutorial from Allan Block. This will help you understand how to work with their system to determine the amount of blocks you will need for your project. Retaining wall blocks range in size from 12-18 inches long and 4-6 inches high.
- Make sure you consider water drainage for your block retaining wall. For a small wall tiered wall, the gravel backfill should provide enough water drainage. You will need to take this into more consideration if you are planning a high retaining wall.
Gather Your Tools
- Safety glasses
- Plate compactor
- Rubber mallet
- Tape measure
- Gravel with pieces ranging ½-¾ inch
Building the Retaining Wall with Blocks
1. Clear the section of any grass and other plants to get down to the dirt level. Haul away the excess dirt as this cannot be used as fill dirt because of the excess roots and debris.
2. For tiered or step-up retaining wall, begin with a base course on the lowest section of wall.
3. Dig a base trench that is about 24 inches wide (600mm).
4. Determine the depth of the base trench by calculating the height of the tier. Dig the trench 6 inches down for each 1 foot of wall height. For this low wall, just a 6 inch deep trench was needed.
5. Fill the trench with small gravel. This will provide a strong foundation for the wall.
6. Compact the base of 2-3 inches of gravel with the compactor tool with at least two passes for maximum compaction. Check the level to make sure the foundation is level. A gravel base of this height allows you to sink half of the block into the trench to create a stronger foundation layer.
7. Excavate the next tier by digging out another trench. Determine how high and far back you should begin your digging based on the height of the wall of the first tier, the slope, and number of levels. Position stakes at the bottom and the top and tie a string in between to help with determining the slope.
8. Dig a trench that is 24 inches wide and 6 inches deep. Layer with gravel and compact twice to create a firm foundation. Check the level of the second trench.
9. Begin positioning the retaining wall blocks in the base on the bottom trench. Place the block against the front of the trench and side to side. As you work, check the level of the blocks to make sure they are level on the foundation. Use a rubber mallet to get each block level.
10. In the open space behind your course of blocks, pack a 2-3 inch layer of gravel. Compact the dirt behind the vertical layer of gravel. This is an important step to make sure your walls do not cave under pressure.
11. Once you have completed the base course in the lowest tier, move to the second tier and complete the base course. Once these courses are finished and level, you can begin the second course on both tiers.
12. Take a broom and sweep off the blocks to make sure no debris is caught between the blocks. Offset the seams of the first course of blocks with the second course of blocks making sure that the seams of each group of blocks are not aligned.
13. Position the depth of the second course of blocks back into the dirt just an inch or two away from the front of the first course. This provides a way for the wall to handle the pressure of the dirt behind it without pushing forward over time.
14. Check the level of the second course. Adjust as needed with a rubber mallet or more gravel. Add gravel behind the second course and compact the dirt behind the gravel.
15. Excavate the third and fourth tier and repeat the steps for laying the courses.
16. Dig side trenches into the hill if you want perpendicular blocks to connect the tiers. Use the same trench size and methods for filling, tamping, and leveling to create a stable base for the blocks.
Types of Blocks for Retaining Walls
Block retaining walls are just one of the many types of retaining wall materials available. Retaining wall blocks are one of the most common materials for DIYers. Compared to other materials, these blocks are less expensive, easy to use, and come in a variety of sizes, shapes, and colors. There are three main types of retaining wall blocks: standard concrete blocks, split faced blocks, and retaining wall system units.
- Standard Concrete Blocks – These are the most basic type of concrete block. They are strong, durable, and inexpensive. These blocks work well to provide a stronger base for outdoor walls with stone facades or wood. Standard concrete blocks have two identical openings that you can fill with concrete for extra reinforcement. Many building codes require extra reinforcement for retaining walls over 4 feet high. Concrete blocks are an excellent choice because of their strength and low cost.
- Split Faced Block – Split faced block is a concrete block that features a custom texture on one side. This provides a side to create a more attractive wall. This eliminates the need for an expensive veneer like stone or brick. Split faced blocks come in several different colors and unique textures so that you can customize your wall to your preferences.
- Retaining Wall Systems Unit – Retaining wall systems are one of the most popular options for DIYers. These systems are designed to create a structural wall unit with a stone-like face. Different wall systems from companies like Allan Block and Versa-Lok fit together in their own way. Each group customizes their own blocks to provide customers with different options regarding color, texture, and size.