September 24, 2020

What makes a Retaining Wall Work?

There are two types of walls to consider when asked the question “what makes a retaining wall work?”  Gravity walls and reinforced walls.  First, let’s look at gravity walls.

Gravity walls require two things to perform well – the Allan Block unit (its weight) and the setback the unit has.  What is “setback?”  Setback is the degree to which a retaining wall “leans” back from vertical as shown in the gravity wall section below.  This setback, coupled with the weight of the block itself, will allow the wall to perform as it should in a “gravity wall” application.  Check out our setback charts for additional information.

Reinforced walls require three things – the Allan Block unit (its weight), setback, and geogrid.  Since we have identified what setback is, the only potential unknown is geogrid.  Geogrid is a woven textile that has been used to strengthen soil for decades.  Reinforced segmental retaining walls utilize geogrid to strengthen soil and create a mass heavy enough to resist the active forces of the soil behind the wall, ultimately allowing us to build taller walls.  A typical reinforced Allan Block section is here:

To learn more about gravity walls or reinforced walls please visit and/or call us today to discuss in more detail. 

September 17, 2020

Should I be Worried About Water Runoff While Building My Retaining Wall?

Water is enemy #1 for all retaining walls, and must be managed with post construction management details as you will see in our water management section on  When water is present in soil behind a retaining wall, it will add significant weight and pressure to the wall which may cause concern.  For that reason, routing water away from the wall after—construction and even during construction—is a Best Practice for Segmental Retaining Wall Design and should be done whenever possible. 

As read in Chapter 6 of the Allan Block’s Best Practices for SRW Design manual, backfill should be graded to avoid water accumulation behind the wall, or in the reinforced zone at the conclusion of each day’s construction. This may require a temporary berm at the back of the reinforced zone as outlined in 6-11 on the detail below, indicated by the red arrow.  This is done to help reduce the amount of water that may accumulate behind the wall, which adds weight and pressure that the wall was not designed for.  For more tips on construction, including water management details, visit our Retaining Walls by Allan Block guide or our Design for Water section that outlines post construction recommendations and the potential need to temporarily control water during construction.

September 10, 2020

How do I Figure Out How High My Retaining Wall Should be?

Retaining walls help us offset grade changes to create usable land on our property.  There are two ways a wall will be constructed, and they are referenced as a “cut” or a “fill” site.  A cut site is one in which you will cut into the hillside to add flat land, and a fill site is one which you will add soil to and raise the land to flatten out the area.

In order to properly size the wall, we will need to have a detailed understanding of site elevations and grade changes to determine wall heights.  Starting at the lowest point on your site, mark your grade changes in 1 ft. (0.3 m) increments on the plan. Mark your elevations on a drawing like the one pictured. 

You may find it easiest to use string lines and line levels to create the elevations on your site. Determine the elevation (height) you want to “fill to” or the elevation point you want to place your wall and “cut” into.  This point, or elevation, will be your standard/benchmark.  From the point you just created, run a string line away from it towards the low spot on your property and/or to the point that will be the low part of your wall.  Keep the string level by using a “line level” and pull the string all the way to the low spot on your site.  Use a stake to hold the string in place and ensure it is pulled tight.  Now, mark the elevations in 1 ft. (0.3 m) increments up to the standard/benchmark identified at the beginning.  Using this technique will help you understand how tall of a retaining wall you will need to build. 

September 3, 2020

How Much of the Base Course Should I Bury?

One of the great things about segmental retaining walls (SRWs), is the fact that the installer does not need to excavate to frost depth and/or pour a concrete footing below the structures. This helps reduce cost and speed up the installation of the systems.  SRWs are flexible in nature, and only require minimal burial below grade.  So, how much block do I need to bury on my first course?  The industry recommends that your first course be buried a minimum of 1ft (2.5cm) for every foot (.3m) in wall height, or 6ft (15cm) (whichever is greater) if the ground in front of your wall is flat.  

For unique applications where a slope is running away from the face of the wall (pictured below), the industry has a different recommendation of 5ft (1.5m). This means that though you have a slope downward, the soil against the block is still 5ft (1.5cm) deep. the burial outlined in both situations helps reduce the likelihood of erosion at the front face of the wall.

August 27, 2020

What Would you Suggest for Hiding the End of the Wall?

There are many ways you can hide the side of Allan Block units when finishing your wall.  While it is not necessary to do for structural reasons, one may decide to hide the side to avoid seeing an “unfinished” end.  There are two ways we want to address today:
First, you could incorporate AB Corner Blocks from any of our collections that are finished on two sides to help hide the end of the wall units.  Simply use a corner block as shown below to return the wall into the retained soil and then miter cut caps to finish the wall as shown here:

Second, you could incorporate AB Lite/AB Barcelona/AB Aztec Lite units to step the wall down in 4” (10 cm) increments to hide the side of the block.  If your AB manufacturer makes AB Lite/Barcelona units, this may be the easiest and more economical method to hide the end of the wall, but check on availability before a decision is made.  This is seen below:

Finishing the wall and “hiding” the side of visible units may prove to be just the finishing touch you need for your project.  Don’t hesitate to call us or check out our Retaining Walls by Allan Block brochure for additional installation tips.

August 20, 2020

How do I Calculate the Quantity for a Circular Seating Wall Around a Fire Pit?

So you’ve already designed an Allan Block firepit using our step-by-step guide, and you’re looking for your next project? If you want to design a seating wall and don’t know where to start, then grab your smartphone or tablet!  Allan Block has a free app that lets you design and estimate your perfect seating wall.  Customize the size and style with the flexible AB Courtyard Collection
First, determine the length of your seating wall.  If you would like the wall to curve around parallel with your fire pit, then you can select the XL curve style in the element selection screen.  Decide on the heights of the walls and posts, and you are done!
Get a rough estimate right on the screen, or submit your project and receive a full estimate report with detailed drawings for free in your inbox.  The report also includes a list of your local dealers where you can go and get your materials.
 Don’t be afraid to add your own unique touch by adding posts, inlaid lighting, or anything you can dream up. The possibilities are endless!

For a better understanding of how to install courtyard walls, and also a visual of parallel curved walls, visit our courtyard reference guide

August 13, 2020

Top 3 Ways to End your Wall

Here at Allan Block, we love retaining walls. However, every great wall needs to come to an end at some point, and we’re here to share our favorite ways of doing so. The look and feel of the wall can change completely depending on how you decide to approach the endings. Luckily, the versatility of Allan Block allows for several different finishing options, each with its own unique style. While there are countless ways to finish off a wall, these three methods are some of our favorites:

1.  The Step Down
            A step down is probably the most common way to end your wall. A step down is exactly what it sounds like; the top of your wall gradually steps down until it is even with the grade. This is a great option because it provides a subtle way for your wall to slowly shrink until it’s completely gone. A step down can be made even more smooth by using our AB Lite Stones, AB Aztec Lite, or AB Barcelona blocks as a way to transition from one course down to the next.

2. The Turn-In
            The turn-in is a popular finishing option that is great for steeper grade changes and a quick end to the wall. With a turn-in, the wall turns directly into the hillside and gets built “into” the hill. This is also one of the easiest methods to end a wall since you won’t need any corner blocks, and instead of the wall slowly stepping down, you can end it almost immediately.  For a more bold, sharp transition into the face of your hill, you can use a 90° corner rather than a curve.

3. The Planter
            A planter is the perfect choice for making the most of your space. With a planter finishing option, you would finish off your wall at different courses, leaving gaps between wall endings to use as a planting space. The planter endings can be designed as either of the options listed above. Also, you can choose whether you want your planter segments to subtly break away from your wall with curves, or create a more pronounced planter by using 90 degree turns at each step-down.

While there is no “best” way to end your wall, each finishing option achieves a different look and feel to it. Maybe you want a bold look and decide to go with a 90° corner turn-in. Or maybe you are going for more of a soft discrete feel and use a step down with caps for an even smoother transition between courses. Regardless, all finishing options can look amazing.

August 6, 2020

Measure Twice - Cut Once (Using the Estimating Tools)

Allan Block has created estimating tools that will help you design and estimate your projects.   These tools are a great recourse to help you estimate your building materials.  Retaining wall materials are not convenient to run to the store to return or get more.  Ordering the correct amount the first time is important. 

Allan Block has tools that can help you determine just what is needed to complete the project.  Each of our estimating tools have been customized to help specific customer groups.

AB Retaining Wall Design and Estimating App (Windows, Mac, iPhone and iPad)
Courtyard Patio Walls Design & Estimating App (Windows, Mac, iPhone and iPad)

Contractors / Builders:

Engineers and Architects:

AB Walls (Windows only)
Contact Allan Block for information about AB Walls -

By using our apps or software, you can receive a 3D image of your project, along with the estimate, to have a visual before it’s built.

July 30, 2020

How Long Will the Wall Last?

The approximate life of a concrete retaining wall could be between 50 – 100 years, though the National Concrete Association estimates it at 75. This will greatly depend on the quality of installation and the condition of the site.  The soil it is built in and the materials used to construct the project, are key to ensure a proper foundation is beneath the wall and water has been addressed. The next factor is how water is being directed away from the wall.  Water that pools above or within the wall adds pressure to the project and over time may, at a minimum, wash out the base materials which will weaken the wall and limit its lifespan.   But by following the Allan Block installation guidelines, any project should perform for many years.

July 23, 2020

How Does a Retaining Wall Work?

A retaining wall retains soil similar to how a dam retains water.  A dam’s mass must be large enough to withstand the pressure of the lake that it’s holding back. A retaining wall’s engineering principles are similar.  Even though earth doesn’t move as fast as water, it still applies pressure to a retaining wall just as water does to a dam.  

Dams and retaining walls are also similar in how they are designed.  Many dams are created using compacted soil that is protected with concrete or rocks.  Retaining walls use a similar design where engineers combine compacted soil with geogrid.  Geogrid is a structural building material that helps consolidate the soil into a stronger mass.  It’s a similar concept as putting rebar into concrete.  The combination of soil and geogrid makes a perfect structural reinforcement for retaining it all.  The concrete retaining blocks are the finishing material that adds beauty and provides protection to the soil mass.

A properly designed retaining wall will last a lifetime as long as the compacted mass is protected from water saturation and erosion.  Engineers design many features into their designs to protect it from these situations.  Properly designed retaining wall structures provide pathways to remove excess water from the base and also behind the wall facing.