A few months ago we were contacted to give an estimate on replacing a failing retaining wall in Goldsboro Pa near the Susquehanna River as well as install a new brick paver walkway from their new deck to the pool. I will mainly discuss the retaining wall portion of the project.
It was a short retaining wall averaging between 2 to 2 1/2 feet tall around a pool area. The wall was leaning toward the pool and continuing to lean farther every year. The customer wanted a new wall installed that wouldn’t have the same issues also adding to the look and function of the pool area.
When meeting with the customer and looking at the failing retaining wall we discussed a plan to improve the functionality as well as longevity of the wall. The customer wanted to gain a few spaces in the area for pool storage and also an entertaining area. We designed a recessed area in the corner of the wall at one end and another recess where they can later put a small storage shed for pool toys etc.
The most important reason for calling Bulloch Lawn Care was to replace the retaining wall with one that wouldn’t lean within a few years. After removing the old retaining wall it was easy to see why the wall failed. Some would guess that it failed due to the base of the wall not being buried deep enough or not having enough crushed compacted stone base material under the wall which are common reasons that many retaining walls fail. This was not the reason for failure for this wall.
This particular retaining wall failed due to drainage issues. We were surprised that we found a drainage pipe at the base of the retaining wall as we were removing it, since usually having a pipe there eliminates the hydrostatic pressure of water behind the wall giving a way for the water to drain away. The problem did indeed lie with the drainage pipe. Even though a drainage pipe was behind the wall, at some point someone cut and buried the end of the pipe where it drained when they installed a concrete walk to the pool area. This started the process of the retaining wall failure.
There are a few reasons that retaining walls fail. Lack of proper drainage is one of the most common ones. Each time that it rains without a way for the water to escape from behind the wall more pressure is pushing on the back than it is designed for. The worst part occurs in the winter months when the water that is behind the wall freezes and creates so much force that it can push a wall as much as a few inches over the course of just a few months. Imagine the space behind the wall developing the force of an iceberg pushing on it away from the earth that it is holding back.
A little thought needs to be put into the design of the drainage system. On some walls they can be drained through the face of the wall at its base. This is a very common way of dealing with the retaining wall drainage system. Where a retaining wall boarders a concrete patio this isn’t the best practice since it would put all the water from behind the wall on the concrete. In this case we look for a lower area in the yard to run the drainage pipe to where it will drain out and not affect the areas closer to the home or entertaining areas.
As we were laying out the pipe behind the wall we made a trench to bury the pipe that led the water farther away. We dug the trench about a foot deep and made sure that it was pitched down as it traveled away from the wall. The reason that the pipe was buried a foot deep was partly due to it going under a brick paver walk that we were installing there as well. With the top of the pipe being 8″ below the surface where the pavers were being installed it gave enough space for a proper base to be installed under the brick pavers.
The wall that we removed and replaced was made with small 4″ high garden blocks that were glued together. With proper installation these walls can last for many years. They are on the lower grade of retaining wall products though. Since they are much smaller weighing about half as much as most retaining wall blocks they are easier to move and install. But since they are lighter they can be easier to suffer failure from pressures behind as well.
The old wall was installed with no setback on each course. The face of the wall went straight up. I don’t recommend this because with each course of the wall that has slight pressure pushing from the back of the wall it doesn’t distribute the force into the ground evenly. When a wall has even as little as a one inch setback per course this helps put the forward pressure of the wall back into the base and ground closer to the center of the block.
As you could have guessed, the new retaining wall that we installed had a one inch setback per course and the block was 8″ high. Each block also had two open section going down between the blocks. The open sections have two purposes. The block weighs less than it would and has a larger width front to back giving the wall more mass. The other benefit is the void gets filled with gravel and tamped over locking each course together. This also gives a great way for water to drain to the bottom that may have gotten into the wall.
The other portion of the project was a walkway and patio area. The brick paver walk that we installed was mainly to connect the pool area to the new deck that was just installed. The new deck had steps leading down closer to the pool area than the deck that it replaced. Since the steps were in a different location it left a concrete walk leading to part of the deck where there was just railing.
We removed the old concrete walkway and made way for a more functional aesthetically pleasing brick paver walk. The walk that we removed was under 3 feet wide in width. When you have large entertaining spaces that the walk is connecting a skinny walkway can make it difficult for the people trying to get from one area to another. I designed the new walkway to be around 4 feet wide. This can accommodate two people comfortably passing each other.
As with many of our jobs, since the client liked how the retaining wall and walk were being done they asked us about adding a brick paver patio to the project. We gave them a price on the change order and after they signed we ordered additional material for the patio.
Since the new deck was quite large and they had space around the pool to entertain as well the patio didn’t need to be very big. They would be putting a few chairs there leading up to a fire pit.
The total cost of this hardscape project including brick pavers and retaining wall came in a little under $16,000.00 The price of each job is different depending on the size and complexity of the installation. Call or message Bulloch Lawn Care to help design and install a backyard that you can enjoy.
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