Building a retaining wall with Allan Block is easy. In this article, we will walk you through the process of building an AB Retaining Wall for your next landscape project. The first step in any project is to determine if it’s an appropriate DIY job or if you need to hire a professional contractor with experience building these kinds of walls. Remember that there are many variables when installing an AB Retaining Wall and the above steps are meant as a guide only. If this is your first time installing a retaining wall, its important to talk with your local Allan Block dealer so they can answer any questions you may have about proper construction techniques and materials needed for your specific installation.
Why do I need a retaining wall?
A retaining wall is a structure that holds back soil, rock and water. Retaining walls can be used to create level areas for a driveway, patio or walkway. They are also used to create level areas for house foundations or to hold back deep soil from eroding away.
Retaining walls are designed with two types of materials: stone blocks and reinforced concrete. Both types of materials will last for many years with proper care but there are some advantages and disadvantages associated with each type that you should consider before making your final decision about which one best suits your needs.
Determine what kind of retaining wall you need
You’ve got a project in mind, but figuring out what kind of retaining wall you need is the first step to getting it done. To help with that, we’ve put together a guide to help you determine which type of retaining wall is right for your landscape needs.
- First, take into consideration what kind of soil you have at hand. If it’s sandy or very porous, then a rubble concrete block wall is probably not going to work well due to its poor drainage characteristics – in fact, it could even lead to drainage issues as water pools against the backside instead of draining away naturally through holes in between blocks (this would be particularly problematic if there were plants growing close behind). On the other hand if your soil has more clay content and holds moisture better then you might consider using concrete blocks instead because they’ll retain moisture better than stone ones will; however this means that those same plants will suffer from lack of oxygenation during dry spells so keep an eye on them.
Decide how large your Allan Block retaining wall needs to be
Before you start building, it’s important to figure out what your wall will look like and how big it needs to be.
The first step is to calculate the amount of material you’ll need based on the size of your AB wall. For example, if you have a 20’x20′ area that needs retaining and drainage, multiply that number by 2 (because your block faces will be on both sides of your wall) which means you’ll need 40 blocks total.
If you want to add a layer of gravel between each level, double that number again for a total of 80 blocks needed for this project—or an average cost of just under $200 per linear foot.
Now that we know how many blocks we need let’s calculate how much concrete we’ll need…
Check with your local building codes office to see if a permit is needed.
Check with your local building codes office to see if a permit is needed. If you need a permit, you may need to hire an engineer. Hiring an engineer will cost more money. You should contact them before you begin building your retaining wall in order to avoid being required to tear down the retaining wall or rebuild it using different materials (which could be significantly more expensive).
Choose a location that is as level as possible. The top of the AB Retaining Wall blocks should be at the same height.
You’re going to have a much easier time building your AB Retaining Wall if you start with a flat surface. If you don’t have one, however, there are some things you can do.
- Build the base of your retaining wall first – then build on top of it!
- You can make a sub-base for the retaining wall first, and then build on top of it.
- Add stakes to keep everything in place while you work on leveling it out and building up (if necessary).
Add 8″ or more of compactable granular base material under the entire course of block. This will help prevent the soil from pushing through the joint and stopping the AB retainer wall from failing in the future. See illustration below for placement of this material.
- Add 8″ or more of compactable granular base material under the entire course of block. This will help prevent the soil from pushing through the joint and stopping the AB retainer wall from failing in the future. See illustration below for placement of this material.
The first course should have 12-14″ wide footing (usually wider than the bottom of the block) and be at least 6″ deep. For best results, pour concrete base so it is level and flat on top. Once cured, place the AB Retaining Wall blocks directly on top. You will want to try to extend this footing out at least 2′ on both sides of the wall.
The first course of AB Retaining Wall blocks should have 12-14″ wide footing (usually wider than the bottom of the block) and be at least 6″ deep. For best results, pour concrete base so it is level and flat on top. Once cured, place the AB Retaining Wall blocks directly on top. You will want to try to extend this footing out at least 2′ on both sides of the wall.
The first course of block will be buried 2-3″ into the ground to help prevent frost heave in areas that get freezing temperatures. (If you are not in such a climate, you can put this first course at ground level). If frost heave is an issue in your area, you may want to add rebar down through holes in the blocks and into its footing for added strength
The first course of block will be buried 2-3″ into the ground to help prevent frost heave in areas that get freezing temperatures. (If you are not in such a climate, you can put this first course at ground level). If frost heave is an issue in your area, you may want to add rebar down through holes in the blocks and into its footing for added strength.
Allan Block retaining walls are built with extra vertical stability so that they do not fail due to frozen soil expansion and contraction caused by temperature fluctuations.
Conclusion
You’ve thought about it, planned for it, and now you’re ready to build your Allan Block retaining wall. Chances are you came here because you want to do the job right and make sure your wall stands the test of time. This can be a daunting project for any beginner, but with these simple instructions and tips, you should be able to get started in no time.
