Retaining Walls
One of our specialties at Redwood is well built, beautiful retaining walls. Unfortunately, we see poorly designed and poorly constructed walls all the time. If you're going to invest in a retaining wall for your landscape, use someone you trust. With years of experience, we've got the expertise to get the job done for you the right way the first time.
Retaining Wall Uses
Retaining walls are incredible tools and one of the most commonly used products in the landscape industry. That does not mean, though, that they are right for every landscape. Here are 4 proper uses for retaining walls.
1. Correct Your Grade or Slope
Perhaps the most common use for a retaining wall is to correct or alter the grade of a landscape. Many homes are built on steep lots, minimizing the amount of usable space for turf or outdoor living spaces. Adding or removing fill dirt to change the slope can help in some cases; however, retaining walls, when constructed correctly, provide a strong, more stable, and more convenient solution. Hills need to be maintained, and in many cases, there is not enough space to allow for a safely sloped hill. Retaining walls maximize the available space and allow homeowners to set their grade exactly as they would like it to be.
​
2. Add Space to Your Landscape
In urban and suburban areas, outdoor space is hard to come by, especially if the property is not flat. Every square foot of space is valuable! Well positioned retaining walls provide homeowners with more space for turf, patios, pools, fire pits, and many other outdoor living space options. If your property slopes down away from the home, adding a retaining wall at the back of the property and raising the grade with fill dirt can transform an unusable area into a backyard oasis. The reverse can also be done! If your property turns into a hill at the back, we can cut out the bottom of the hill and replace it with a wall, adding hundreds or even thousands of square feet of space!
​
3. Solve Drainage Issues
Perhaps the greatest potential obstacle in any given landscape design is water flow. When homes are built, a water plan is designed and approved to ensure that the property will not deal with drainage issues. Even so, due to poor design, poor execution, or changing site conditions, many homes end up with massive water headaches. One common problem is when berms, meant to direct water, settle or shift, causing the original water shed plan to fail. Retaining walls can solve this problem by permanently reestablishing the berm. Even if no berm previously existed, walls can be installed to alter the grade enough to correct problematic water shed patterns.
4. Beautify Your Property
Well designed retaining walls can take your landscape to the next level. Your slope may be manageable, but retaining walls add contrast, interest, and a feeling of strength and stability. Walls can be used to set apart different areas of the landscape, giving the effect of different rooms or spaces in the yard. Rather than having a sloped walkway down to your patio, use a wall with a built-in staircase. Your landscape will be sure to stand out above all the neighbors.
​
​
Retaining Wall Construction
Proper retaining wall construction is absolutely essential. Walls are not just decorative; they have to be able to withstand any forces that are or could be applied, including water, vehicles, and even the dirt used to backfill the new wall. When walls are insufficiently engineered, or improperly installed, it is only a matter of time before they will fail, causing damage to the landscape and requiring immediate attention. If you need a retaining wall, use a contractor you trust.
​
Here are the 6 steps a good contractor will follow to install a stone block retaining wall.
​
1. Prepare the Base
Just like a house needs a foundation, a wall needs a base. Before any blocks are installed, the installer will excavate a large trench. Most blocks are 12 inches in depth, so the trench will need to be 18 to 24 inches in depth or more to ensure that the block is on solid ground on all sides. After removing the dirt from the trench, 6 inches or more of 57 stone (or some other angular aggregate) will be installed and compacted in the trench; this gravel has a high compaction rate and thus provides a fantastic foundation for the retaining wall blocks. When the base in installed, compacted, and leveled, the installation crew is ready to add block.​
​
2. Install Block
Typically starting with the low point of the wall, block can now be laid on top of the gravel base. Each block must be individually leveled from front to back and left to right. It's essential to get the base level; if it's off, the top of the wall will be uneven and, if the imperfection is great enough, potentially unstable. This step is the hardest and most time consuming, bu​t when done correctly, the rest of the installation process is a breeze.
​
3. Add Drainage Pipe
At least one 4 inch perforated drain pipe will be installed behind the first row of blocks to allow any water trapped behind the wall to escape. This step cannot be overlooked! Walls without drainage act like damns; given enough water, they will eventually break! If the wall covers a large number of linear feet, or if the low spot in the wall is in the middle of the wall, cuts will be made into the second row of block to allow the water to exist through the wall opening. If the wall is smaller, water will be allowed to drain out both sides of the wall. After the drain pipe is installed,
​
4. Back Fill and Core Fill
With the first two rows of block and drainage pipe installed, the installation crew will begin back filling and core filling the wall. 57 stone is used for both. At least 12 inches of gravel should be installed behind the wall from the base to the top of the wall, only living a few inches for top soil and sod on top. This gravel allows any water that flows into the wall to drain quickly into the drain pipe and away from the wall. 57 stone will also be used to core fill the blocks. Most retaining wall blocks come hollow to decrease the cost and weight of the product. To ensure stability, though, the gaps must be filled with gravel, to compensate for the lack of weight. This step is commonly skipped, because when the wall is finished, it's impossible to tell if the wall has been core filled or not. Make sure that your contractor core fills the entire wall. This is typically done after every two rows of block are installed. ​
​
5. Install Geogrid Textile Fabric (If Necessary)
If the wall is over 4 feet tall, or if the site conditions call for greater structural integrity, geogrid should be installed. Versa-Lok explains that "Geogrid is a geosynthetic material, made of polymers, that is used to reinforce soil behind retaining walls. Installed in horizontal layers between wall courses and extending into the soil behind a wall, geogrid stabilizes the soil and so increases a wall system's mass and stability." Typically, geogrid should be installed as deep into the hill side as the wall is tall.
​
6. Install Caps
When all blocks have been installed and core filled, caps can be installed. Unlike retaining wall blocks, which are made with a trapezoidal shape to allow for curves in the walls without cuts, caps come in rectangles, and therefore must be cut to size to fit any curves in the shape of the wall. After cuts are made, caps are glued to the top row of block with an outdoor construction adhesive.
Types of Retaining Wall Material
Most retaining walls we build are constructed with Belgard Diamond Pro blocks and caps. Belgard sets the industry standard for retaining wall blocks. This product is 18 inches wide, 12 inches deep, and 8 inches tall, making the face of each block equal to one square foot. Diamond Pro come in a variety of colors, including Stone Grey, Buff, Carriage House, and Sheffield Beige. Check out color options here.
​
These blocks share the same design and color options as the Diamond Pro blocks, but are 9 inches deep instead of 12 inches deep. This newer product was created after extensive research showed that 12 inch deep block was unnecessary for retaining walls less than 4 feet tall.
​
Weston wall blocks by Belgard are designed with different purposes in mind. All four sides of the block is finished (unlike the one sided Diamond Pro block), which makes it a great product for sitting walls! Weston wall blocks are also fire rated, so they can be safely used for fire pits!
​
Techo-Bloc offers a wide selection of high-end retaining wall and sitting wall block options. While these blocks will cost significantly more than a Belgard wall, their design appeal makes them worth a second look.