A retaining wall is a landscaping element that helps us to beautify our yards despite our terrain. Your personal property may not be suited for your landscaping needs.
Therefore, retaining walls can help you flatten the area or create beautiful beds and terraces. Also retaining walls are perfect to help you promote good drainage on hilly landscapes without soil erosion.
What is a Retaining Wall?
A retaining wall is a structure that holds soil in place behind the wall and stops the erosion of the material inside the wall. Most retaining walls are built on a slope where the change in elevation would be too steep to prevent the soil erosion on its own.
Retaining walls are all around, though many of us do not notice. You can find them in parks, city centers, sports arenas, and many personal yard spaces. Retaining walls have two main functions: to level sloped land and to prevent soil erosion.
A retaining wall is vital in the construction of terraced landscaping, sunken patios, and the creation of flat areas on hillside landscapes.
Retaining Wall Materials
There are many kinds of materials for building retaining walls. Each has benefits and drawbacks and you should consider each kind to see what would work best for you.
Wall Block Retaining Wall
Retaining wall blocks are designed for the specific purpose of use in the creation of small to mid sized retaining walls. There are both residential and structural retaining wall blocks.
The residential blocks are designed for walls in a home landscape. Manufacturers provide them in a range of colors and sizes to suit many different landscaping styles. If you want to make retaining walls taller than 3-4 feet, you should use structural retaining wall blocks rather than residential.
Concrete Block Retaining Wall
Concrete blocks are one of the most cost-effective choices for retaining wall construction. However, this is not an attractive option. Thus, many people will use concrete blocks to provide the structure of the wall and use stone as a facing on the wall for decorative purposes. Others use concrete blocks as the facing of the wall. Interlocking concrete blocks will form a tight and stable retaining wall.
Natural Stone Retaining Wall
Many people love the look and style of natural stone retaining walls. If you like this look and money is no object, consider natural stone like limestone, sandstone, granite, and fieldstone to build a retaining wall.
Wood Retaining Wall
Another cost-effective choice is to use wood. While wood is not as long-lasting as stone or concrete blocks, it does create a natural look that many prefer. Wood works very well in areas like gardens for raised beds.
There are many wood options, and you should consider their look and lifespan to determine if a wood will work for you. Some common choices include cedar, redwood, pressure treatment lumber, and Douglas fir. People have used railroad ties in the past, but these contain toxic chemicals that leach into the soil and are better avoided.
Sheet Pile Retaining Wall
Most sheet pile walls are built for construction purposes rather than residential purposes to hold backfill material for the time that construction is progressing. Most sheet pile walls are built using thin material like steel fabricated into interlocking sheet piles that builders have driven into the ground and laid in a consecutive vertical manner.
Brick Retaining Wall
Bricks make for an attractive retaining wall, though a single layer of bricks is not enough to build retaining walls that will stand the test of time. If you want to use brick, you must construct a block core wall or use bricks as the facing on another material such as concrete blocks.
Poured Concrete Retaining Wall
Poured concrete is a cost-effective choice, but it does require some skill to get this method right. The risks of using poured concrete include cracking and bulging. If a crack appears in the wall because the formulation of the concrete is inaccurate or because there is not proper drainage, it is difficult to correct.
In addition, if the forms are not accurate, bulging will happen in the wall and decrease its attractiveness.
Retaining Wall Cost
The total cost of a retaining wall depends on the building materials you use and the retaining wall labor cost. The costs listed below include both materials and the cost to install a retaining wall for professional landscapers. These costs come from HomeGuide.
- Wall block – $15-$55 per square foot
- Concrete block – $20-$35 per square foot
- Natural stone – $20-$85 per square foot
- Wood – $10-$40 per square foot
- Metal – $15-$30 per square foot
- Brick – $30-$60 per square foot
- Poured concrete – $20-$45 per square foot
Checklist Before You Begin Digging
- First, you want to decide on your landscaping needs to see where you should build your retaining wall for the best effect and the most efficient use of space.
- Next, decide what kind of style you like. This will determine the type of materials you use for your wall. For example, if you want to create an English cottage style for your yard, use a material like natural stone or brick. If you have something more contemporary in mind, try poured concrete or even metal sheeting.
- Then, check up on your local building codes. These vary from state and state and even town to town. Thus, these will give you a guide on how high you can build a retaining wall without requiring a building permit. If you need to build a higher wall than you thought, you may need the services of a structural engineer to help you plan.
- Contact your utility companies to see if there are any gas lines, cable lines, water pipes, and so on, running through the area you want to build a retaining wall. If there are, determine the location and work around them or get the companies to run a new line.
- Consider any water issues that may come into play as you plan where your your retaining wall will be. Make sure that the wall provides proper drainage when heavy rains fall.
Building a Block Retaining Wall
Building a retaining wall is a project that you can take on yourself. This section is not a step-by-step tutorial, but it will give you a good overview of the materials you need and steps you will take to build your wall.
If you need help with deciding how much building materials are required for your wall, there are handy calculators online to help you with this.
Tools and Materials Needed for Building Retaining Walls
- Safety glasses
- Circular saw with a masonry blade
- Masonry chisel
- Rubber mallet
- Interlocking blocks
- Landscape fabric
- Construction adhesive
- Paver base
Once you have planned the height and layout of your retaining wall, you will be ready to begin building. First, measure and mark the location of your retaining wall with stakes and string. Remember, if your retaining wall is over four feet high, you may need the help of a structural engineer and be required to get a permit for the wall.
Then, you will need to dig a trench for the bottom row of wall blocks. The height of your wall will determine how deep you need to bury the blocks for a stable foundation. Before you proceed, use a hand tamper to make sure that the dirt on the bottom of the trench is compact and level or this will affect the wall’s stability later in the process.
Next, you will need to spread a 4-6 inch layer of gravel into the trench. Tamp it down so that the gravel does not shift when you walk on it. Then, sprinkle some sand into the trench over the gravel. Now, you are ready to lay the first course of blocks.
For the first row, lay the first block and level it. Make sure that each subsequent block you lay is level with that first block front and back and side to side. If you have areas of each block that aren’t level, use a rubber mallet to adjust the level. Next, check the overall level by laying a long board over the wall blocks and check the level.
After you finish leveling the first row and brushing off the dirt, you can begin the second course. Next, use a circular saw or masonry chisel to cut the first block of the next course in half as you need to stagger the seams for each row. Then, lay the row of the second course checking the level as you proceed. Lay the subsequent rows varying the seam and checking the level with each block. Use the rubber mallet to adjust the four corners of each block.
After you have completed the second course, lay down landscape fabric behind the wall. Also, make sure to leave enough excess to reach the top of the wall blocks.
As you complete each row, you will need to use backfill material behind the wall. The most inexpensive backfill material is gravel. First, pack gravel into the back and nooks and crannies of each block. Next, make sure the backfill material is tamped down and that the top of each layer is clean before beginning the next course.
This gravel should be sufficient to provide drainage for a low retaining wall, but more extensive drainage will be needed for higher walls. Also, if your wall is over four feet high or if there is extensive water in the area, you will need to consider adding drainage pipes that come out along the wall or under the wall blocks.
For the last two rows of your retaining wall, follow the same procedure, but use a masonry adhesive to connect each block to the one below it. For the top row, you can use just regular retaining wall blocks or use capping stones for a more formal look.
Frequently Asked Questions (FAQ)FAQ
What is the strongest type of retaining wall?
Concrete, stone, and brick retaining walls are among the strongest types. These last anywhere from 50 to 100 years. On the other hand, wood retaining walls only last up to 40 years.
What type of retaining wall should I use?
The kind of retaining wall you choose depends on the look you want, your budget, and the size of your wall. If you want to create a more traditional or classic look, use brick or stone. These materials have been used in retaining walls for centuries and look seamless in a classic garden. In addition, if you want a retaining wall to blend with the natural surroundings, consider a wood or natural stone retaining wall. If you want a contemporary look, choose poured concrete or metal.
If budget is your greatest concern, choose an inexpensive option like concrete block or metal. Last, if your retaining wall is going to be high, use a strong material like interlocking concrete blocks, structural wall blocks, or poured concrete.
What is the maximum height of a retaining wall?
There is no specified maximum for retaining walls, but there is a maximum to build a retaining wall without structural support. Therefore, if you want to build a retaining wall over four feet, you will need a building permit and some kind of structural support in the wall.
What are the most cost effective retaining walls?
The most cost effective retaining walls are built using concrete blocks or metal sheeting.
How much weight can a retaining wall hold?
Retaining walls hold back an incredible amount of weight. A four foot wall that is held together by gravity with no other structural reinforcement, can hold around 20 tons. However, if a wall is built with strong materials and structural enforcement, they can hold much more.
Retaining walls are an invaluable part of your home landscaping arsenal. While retaining walls have a strong functional aspect, they also bring beauty to your outdoor garden areas.
You can use them to create raised gardens, bring more interest to your sloped yard through terraced beds, and define your outdoor patios with surrounding plant areas.
Make sure that before you begin, you walk through the checklist in order to avoid surprises down the road.
After all, retaining walls can last far beyond our own lifetime, and it is worth planning with longevity in mind.