There are so many landscaping elements that are thought to be similar but actually have very different functions. This is especially true for masonry features such as retaining and decorative walls. While this may not be the most exciting topic to explore, there are significant differences that are important to understand when planning out your landscape walls.
I prepared this detailed guide to help you identify a retaining from a decorative wall structure. We will cover their purpose, look, and some of the materials needed to build them. We will discuss the various types and some FAQs that can be useful to you if you are in the process or planning to build one.
Table of Contents
First off, let’s talk about the role of retaining and decorative walls in landscaping. While their functions sometimes overlap, they are built for different reasons. Let’s take a closer look:
A Retaining wall is meant to keep the earth in place. As compared to other wall types, it is built to be stronger and sturdier so it can hold dirt and preserve the shape of your landscape. They can help stop erosion and can be used to convert slopes into useable spaces.
Below are some common uses for retaining walls:
- Water Runoff Control: A retaining wall can be a very effective way to change the grades of your yard to channel the water where you want it to go rather than allowing it to take its natural course. Your retaining wall can divert water away from foundations and keep the rain from washing away garden dirt.
- Slope Solutions: People who have steep slopes in their yard often struggle with getting plants to thrive on the hillside, which all too often results in erosion problems. Many times, a steeply sloped, unusable sloped area of the yard can be converted into a beautiful and functional terraced garden or even a sitting area.
- Seating: If you are hosting a large gathering, you inevitably run out of seats. Retaining walls can serve as overflow seats depending on their location and height.
- Visual Interest: Retaining walls can be used to create raised beds anywhere in your yard, so even if your yard is flat as a pancake, you can use a retaining wall to create a beautiful raised planting bed.
- Lighting Solution: Retaining walls are an excellent way to set up lighting for your yard. It may not be economically feasible to install a retaining wall just to have some lights. But, if you need a wall anyway or already have a retaining wall, it’s fairly easy to add low volt or line voltage lighting to a retaining wall.
- Maximizing Space: Installing berms and contours in your yard is an excellent way to enhance your landscape, but sometimes you just don’t have enough room to blend in a large berm. Never fear; a well-placed retaining wall can allow you to create a berm of any size and limit its spread on any side you’d like through the use of a retaining wall. Also, if your house is backed up against a slope with a sliver of a backyard, you can dramatically increase your living space by moving that hill back using a retaining wall.
Any other wall that is not retaining the earth is considered a decorative wall. This includes garden walls, seating walls, privacy walls, etc. Although each of these has its own purpose, if we think about it, they are primarily built to add character and visual appeal to your landscape.
Below are some common uses for decorative walls:
- Privacy: When you throw a party or a family gathering, you surely do not want the prying eyes of your neighbors to make your guests uncomfortable. If your yard is wide open to the neighbors, a well-placed privacy wall can make all of the difference. Privacy walls are also a great way to block the prevailing winds and give yourself some nice calm, warm areas in your yard.
- Mood and Aesthetic: A well-planned decorative wall serves as an aesthetic element to your lawn and can also be the focal point of your landscape. Depending on the theme you are going for, it can change the mood of your area.
- Seating: Similar to retaining walls, decorative walls can also provide overflow seating once you invite friends over. Some great examples of these are low walls that accentuate your firepit or patio.
- Division: Decorative walls can be a great way to segment your yard into separate and intriguing areas. Being able to view your entire yard is great for tossing around a football, but if you want an interesting yard, you need some division and intrigue. Use a gently curving wall to lead a path from one planting area to the next, use it to outline a special perennial bed, or use it to back a quiet seating area at the edge of the yard.
- Vertical Gardening: Decorative walls can be more than just privacy or seating structure. They can also be used to garden vertically. Some homeowners opt to plant at its base for a more natural look, while others go for affixing planter boxes and baskets to the wall.
Retaining Wall Basics
Compared to decorative walls, retaining walls can be quite a bit more complicated to install. Here are some of the important basic rules that should be applied to any retaining wall construction.
- Drainage: The most destructive force on a retaining wall is water. There are two ways that water can destroy a retaining wall.
- Water Flow: Enough water flow can wash out the soil behind the wall and cause its failure. The ground behind the retaining wall must be graded to slope away from the wall. If you cannot pitch the soil away from your wall, then your wall is simply not high enough.
- Freezing: Water held in the soil behind a retaining wall will freeze when the temperature drops low enough. When wet soil freezes, it expands. This expansion is a powerful force that will push any wall forward. This is not usually a one-season occurrence, but the wall will be pushed out a bit each time it freezes. Eventually, given enough time, the wall will fail. This is the most common failure that I see in retaining walls. To avoid this failure, you must pitch the ground away from the top of the wall, so water doesn’t flow behind the wall. In addition to this, every retaining wall must be installed with drainage behind it. Different walls require different drainage, but drain tile at the bottom behind the wall, backfill with washed stone, and geosynthetic fabric is pretty standard. Depending on the layout of the wall, it may also require seep holes out the front to alleviate the water. Adequate drainage behind a wall will remove the water to alleviate any freezing concerns.
- Back Pitch: Most retaining walls other than some of the largest concrete and steel commercially installed walls need to be installed with a back pitch so that the weight of the wall material holds it in place.
- Footings: Depending on the installation and your area, the wall may require some type of footing or bottom trench to help tie the wall into the existing soil. Like any patio or walkway, a retaining wall must be built on a solid foundation. All soft, friable material must be cleared away before construction, or the wall will move over time. If you are in an area of the world where the ground freezes, you will want to be sure that any mortar and concrete set walls that you build have a sufficient footing under them to avoid them being cracked by frost heave. It is usually recommended that this footing extend down below the frost line, and in my area of Wisconsin, this is four feet. Dry-stacked walls are often popular in colder regions because they will move with the frost, and no damage will occur.
- Engineering: Most commercially available retaining wall blocks will require engineering plans if they reach over four feet high. Always follow manufacturers’ specifications for the wall that you are installing.
- Limits: Under most conditions, a wall shorter than four feet won’t need special engineering specifications as long as it is built according to the water flow and drainage principles. There is really no limit to how high a retaining wall can be built, but an inexperienced wall builder should not cross the four-foot limit.
- Height Matters: When planning and building a wall, material choice, proper drainage, and height are the most critical aspects. A typically constructed block wall above four feet will require a step-back greater than the height of the wall below and typically geosynthetics sandwiched between layers of the wall to tie it to the slope. Another way to offset wall height is to increase the size of the material. Enough mass and back pitch can also overcome height challenges
The appearance of a decorative wall will depend on its type. But as its name suggests, they are primarily installed for their aesthetic impact on the landscape. They are usually low walls measuring about 18 to 30 inches. They can be built using almost any material that will support its own weight. Since they aren’t holding back any soils, they only need to support themselves. Once again, the taller the wall, the more solid footing they will need.
Examples of Retaining Walls
There are as many types of retaining walls as there are possible materials.
Gravity Retaining Wall
This is considered the most basic type of retaining wall since it only uses weight and mass to keep the soil in place. These walls are based on logic. Enough mass in front of the soil will hold back the ground. It’s simple physics. Walls like this have been built for many generations. The most popular materials for these walls are whatever large stone materials are available locally. Historically, more than today, the weight of rock has limited the ability to move it, so large boulder and stacked rock walls were typically built using local rock. When installed properly, these walls are some of the most long-lived walls because they do not rely on man-made materials; they depend on rock and gravity. While most of these walls have been built of rock, gravity walls can and have been constructed using many different materials such as; large sandbags, stacked tires filled with soil, plastic drums filled with sand, and many more. These container-style materials are typically referred to as gabions. They don’t need to be fancy, just heavy.
Manufactured Block Retaining Walls
These have become very popular due to their simple building block style. Many are installed every year by homeowners and professionals alike. They are relatively straightforward to install, but the basic rules of wall building must be followed, and as stated earlier, manufacturers’ recommendations and specifications must always be followed. If these walls fail, it is almost always due to faulty installation methods, not due to product failure. Many are built using geosynthetics to tie them to the wall, and many are fastened together layer by layer using construction adhesive. While most of these are strong due to the engineering and correct installation, some commercial manufactured block walls are so heavy and large that they are basically gravity walls.
Cantilevered Retaining Wall
Cantilevered retaining walls are really only installed when a large amount of fill is being moved. They are made of steel-reinforced, poured concrete, and are L-shaped The bottom of the L is under the weight of the soil that the back of the L is supporting. The ground above holds the slab so that the wall won’t tip forward. The success of this wall depends on gravity, but mainly on the structure of the L. These walls can be poured on-site or manufactured off-site and transported to the site.
Sheet Piling Retaining Wall
Sheet piling retaining walls are historically constructed of contoured steel pilings. The steel pilings are driven into the ground with specialized heavy equipment, and they are interlocked with each other as they are installed. They can be installed to support almost any wall height as long as the pilings are built thick enough, and they can be driven into the ground far enough to offset the weight behind them. Because they are made from steel and are interlocking, the chance of them pushing forward is very limited. The weakness of these walls is that they are built from steel, which will eventually corrode and fail. It is possible to construct a driven piling wall using timbers and also vinyl, but timbers aren’t interlocking and are very difficult to drive accurately, while vinyl pilings are typically only used as break walls in areas where excavation can be used to install them, and they prevent erosion more than retain soil.
Timber Retaining Walls
These retaining walls were popular prior to the advent of the manufactured block walls. They can be built using any sort of wooden timbers, but the most prevalent wall materials were pressure treated timbers and re-purposed railroad ties. They were usually alternately staked and tied together using spikes and rebar for stability. Since they are not heavy, they rely on angles and buried wall sections to hold them in place. If a relatively straight timber retaining wall was created, “deadmen” were installed to tie the wall into the earth behind it. Deadmen are typically timber installed perpendicular to the wall, between layers, and spiked into the wall above and below it. The back of the deadman is dug into the ground behind the wall and would usually have a cross piece spiked to the end to ensure that it won’t pull out of the ground.
Poured Concrete Retaining Walls
Countless poured walls have been installed over the years, as concrete has been a go-to construction material for many years due to its design flexibility and extreme strength. Concrete walls can be engineered to retain any sort of wall. When in doubt, just add more concrete. Talk about the ultimate retaining wall; most dams are built using concrete.
Examples of Decorative Walls
Since decorative walls don’t retain the earth, there aren’t nearly as many rules or requirements. You can make a decorative wall out of almost any material you find attractive. Taller decorative walls, such as privacy walls, will be much more economical to build out of wood, steel, or vinyl, while the decorative short garden walls are typically made from stone, and patio walls are often built of the manufactured block. Decorative walls are usually constructed so that both sides are equally attractive since they can be viewed from both sides.
This is the general, all-encompassing term for any free-standing, decorative wall built in the yard or garden. They can be used to divide certain landscape features or delineate beds and walkways and create structure in your yard. They are only meant to emphasize some landscape elements and not to withstand soil pressure. Decorative walls are also often used to delineate property lines and used in conjunction with pillars to create grand property entrances. While many garden walls are dry laid, simple, and rustic, formal garden walls can have footings and be constructed of concrete and brick or stone for a very formal, elegant look.
Unlike garden walls, these often use double or single stacked manufactured blocks, and they usually have a cap to create a flat seating surface. While not as popular, seat walls can undoubtedly be built using natural stone, concrete, or brick. Seat walls are often accented with decorative planters and columns topped with lighting for the patio. While these seat walls can support people’s weight and often hold some garden soil, they are not designed to hold back the earth. They are stacked in a similar fashion to the manufactured block retaining walls and are often held together with construction adhesive.
Privacy walls are a worthy addition to your landscape since they can bring security and comfort to you and your guests. They are usually four to six feet tall and often built in a similar fashion to a short section of fence.
Materials Used for Walls
In building retaining and decorative walls, it is easy to get overwhelmed by the various materials you can choose from. Your budget, the wall purpose, and the look you desire should always be considered.
- Manufactured Retaining Wall Blocks: These are probably the most popular type of retaining wall material right now. They are popping up in all sorts of neighborhoods and being used for soil support in road and sidewalk projects. There are varieties, colors, shapes, and sizes to fit any project and taste.
- Concrete Block: This is often used for free-standing, decorative walls as the structural center, which is then covered with brick or stone. It has been used as a stacked structural building block used with mortar to build walls for houses and other structures for generations. It can be left bare but is not particularly attractive
- Stone Veneer: This material allows a lot of flexibility since you can choose from various natural stones. Stone veneer is installed over a poured concrete, concrete block, or wooden framed base. It is typically applied using mortar and wall ties, just like brick veneers.
- Poured Concrete: Poured concrete offers the ultimate flexibility of design and shape. You can pour any shape that you can form, and it is very durable. It is often installed as the footings and foundation of a veneer wall, but it can be used on its own, especially if stamped and colored.
- Brick: If you have a traditional house design, using bricks can complement it. Walls can be built using layers of stacked brick as was done historically on brick wall houses, but are more commonly constructed nowadays using a brick veneer over a wooden, concrete, or concrete block foundation. Brick is typically more prone to absorb water than stone, so it may require a capstone to protect it, and it may be more inclined to crack in freezing areas.
- Wood: Installing wood retaining walls is relatively straightforward, but it has sort of fallen out of style over the last ten years or so. I believe that it has lost its popularity for three reasons. The wood used must be pressure treated or creosote treated, so not great for the environment. Manufactured concrete block retaining walls of greater durability, easier installation, and many color and texture choices. The wood timbers can decay over time, regardless of the chemical treatment.
- Dry, Stacked Stone: Dry stacked stone walls are probably the oldest type of walls. They can be built using flat stacked stone or round or jagged boulders. Since these walls are not mortared and rely only on gravity to hold together, they must be installed correctly. When using natural, local stone, these walls can look very natural and typically go well with any landscape design.
- Gabion: Gabions are basically any sort of container filled with stone, concrete, or sand that is stacked to form a retaining wall. They can be very effective and quick to install. The downside is that if filled with anything other than concrete, you depend on the container’s material for the durability of your wall. These are often used along shorelines as they can be installed from the topside with little shore disruption.
Retaining Wall Frequently Asked Questions
Does a retaining wall add value to your home?
One of the advantages of adding a retaining wall to your landscape is that it increases your property’s market value. Any property with attractive and functional masonry features is more appealing to buyers and can be sold at a premium.
How do I know if I need a retaining wall?
If your home’s foundation or any part of your yard is threatened by soil erosion, then you can likely alleviate this threat through the use of a retaining wall. If you would like to alter slopes or add contours, retaining walls can be used to do this also.
What can I use instead of a retaining wall?
Just about any heavy and stackable material can be used to help retain soil, so be creative and use what you have.
How close to a boundary can you build a retaining wall?
There are specific regulations on how close you can build a retaining wall to your property’s boundaries. As such, you would need to consult your local city council or your area’s building and engineering department before you start constructing a retaining wall.
What is the cheapest type of retaining wall?
The cheapest type of retaining wall is dry stacked and uses readily available cheap materials. If you are a handy person, doing the job yourself will significantly reduce your costs. If you live anywhere near farmers, they often have large piles of stones that they remove from their fields. They may be interested in getting rid of these piles at a real bargain, especially if you will do all of the loading and hauling.
What is the easiest retaining wall to build?
Many do-it-yourselfers seem to prefer the manufactured block walls, and I believe that this is due to the building block style and perceived ease of installation. Personally, I believe that a natural boulder wall is much more attractive, easier to build, and will last forever if constructed properly.
What is the strongest type of retaining wall?
I would say that poured concrete has the absolute highest strength potential since it can be designed and reinforced to withstand any force. Look at the Hoover dam. It is built of poured concrete over 700 feet tall. Now that is an enormous retaining wall!
Do I need foundations for a garden wall?
This depends on the style of garden wall that you are building. Any dry-stacked wall will move with the frost /thaw cycle and should be a problem. Any time you put mortar or concrete into your wall, you will likely want a footing or foundation.
How tall should seating walls be?
For you to sit comfortably in a seating wall, its height should be 18 to 24 inches, and this height should include the capstone.
How do you make an old garden wall look good?
Often, old garden walls become overgrown with plant material, and rocks often shift. To freshen up a natural stone garden wall, remove any overbearing plants and restack any fall stone areas.
Both retaining walls and decorative walls are a worthy addition to your landscape. Although their functions sometimes overlap, knowing their differences is essential if you don’t want to waste your time and money using the wrong materials. Most of this retaining wall knowledge is common sense, and the best way to build a wall is using common sense and patience. A retaining wall is a long-term investment in your property, and it is a lot of heavy material. Take your time building it and always follow manufacturers’ recommendations. If you are new to wall building, a stacked block or boulder wall less than four feet tall should be doable. Anything over that, and you will want to hire a professional or really do your research.