June 17, 2021

What do I do for buildup and efflorescence?


Allan Block is made to last, but what happens when natural buildup and efflorescence happens to the block?

“I have had my Allan Block wall for 20 years. Moss and general dirt have  

            accumulated on my blocks. What is the best solution to spray on my blocks  

            before pressure washing them? Also, is there anything to get the  

            effervescence off the block? I was not aware that the limestone would react  

            with the blocks.”

Great question Jeffery! To remove the moss and dirt simply pressure washing the wall should remove the debris. As for the efflorescence, although it can look daunting, the best way to remove it would be to use a stiff bristle brush and scrub with either a 50/50 vinegar and water mix or a dish soap mix. There are also solutions you can purchase that remove and prevent efflorescence, check with your local landscape store or big box store.


If you have any questions send over them to us or give us a call at (800) 899-5309.

November 5, 2020

Neutralize Graffiti with Our SRW Safe Suggestions

A common question that pops up from time to time, is “What if my Allan Block retaining wall has been graffitied? How can I remove this?” There are a couple of different ways to handle this situation; here is what you can do if you happen to become a target of those pesky vandals –


Prepare & Pre-Treat – If you are wary of this becoming a possibility, or have been subjected to this problem in the past, invest in products that will prevent spray paint from adhering to the surface of the wall. We suggest Block Guard & Graffiti Control II, as it is also a weatherproofer and a safe option for Allan Block products. It is also water-based, and will not alter the block’s natural appearance.

Power Wash – If you unfortunately fall victim to graffiti upheaval, the most effective method of removal is power washing. There are several products available you can use to spray the maleficence away, but we recommend applying Defacer Eraser Graffiti Remover, as it is easy to use and has no harsh solvents within its compounds.


Keep these options in mind when having to confront a defaced Allan Block retaining wall. You can also reach out to us for additional advice at 800-899-5309, or engineering@allanblock.com.

October 29, 2020

Can I Build a Fence on Top of a Wall?

If you want a fence on top of a wall, there are some things to consider. Is the wall already built? If it is, then you have to know how the wall was built; did they use geogrid, or is it a gravity wall? If the wall is in the planning stages, you have to decide the placement of the fence and how it will affect the construction of the wall.

There are many ways to build a fence above a wall. One is to have the fence set 3 feet (.9 meters) behind the back of it. This method is preferred because it does not require extra engineering. This requires construction tubes to be placed during the construction of the wall. If the fence is added after the wall is already built, the fence installer could damage the structural integrity of the wall. If the wall was built using geogrid, they could tear it, which will cause the wall to fail. Instead, they will have to dig the post holes by hand. If the wall is constructed using no-fines concrete, the fence installer will not be able to install a fence after the wall is built.  

A second method is to have the fence directly behind the wall. This requires a fence above the wall overturning calculation to be completed to understand how the fence interacts with the wall. This calculation determines the fence’s parameters; how deep do the posts need to be placed? How far apart are the posts? How tall is the fence? These factors impact the wall, which may cause the top to overturn and fail. To have the fence directly behind the wall, you will have to install the construction tubes during the construction just like the first procedure mentioned. A way to do this is with Sleeve-It. Sleeve- it is a product that is installed during the wall construction, but it does not require extra engineering for overturning. If you have any questions regarding this topic feel free to contact us at 800-899-5309, or email us at engineering@allanblock.com.

October 22, 2020

What is a Gravity Wall?

A gravity wall is a stacked block retaining wall that can stand up by the weight of the stone alone.

Gravity walls are usually shorter in height and consist of block and stone without the use of additional reinforcement.

To determine if your retaining wall can be a gravity wall, check out our Gravity Wall Chart. The chart will let you know how high your wall can reach to still be a gravity wall based on your project parameters.

October 15, 2020

What are my Choices in Color and Style of an Allan Block Retaining Wall?

Since Allan Block has been in business from the beginning of the modular block industry, there are many options available for you to match the look you want on your project. If you’re seeking an antique appeal such as “Old English”, then AB Europa might be the collection to choose. Maybe you want the split-face block and marbled color that is provided with the AB Collection. If those aren’t suiting what you’re looking for, the natural stone appearance of AB Fieldstone heightens aesthetics and differs greatly from the split-faced fa├žade. Brand new to the AB family is the Aztec Collection, which has a smooth, yet textured face to give the wall many dimensions. The best part about using Allan Block products isn’t just that they have a style just for you, but you can find a color available that will accent your backyard to make your outdoor living space the talk of the town! For exact colors and availability, contact your local AB Dealer in your area!

October 8, 2020

What Does an Allan Block Retaining Wall Cost, and How Does it Compare with Other Types of Materials?

In comparison to other types of retaining wall material, Allan Block is very competitively priced.
To touch upon a few common choices, let’s first look at Timber. This type of system works, and has been tried and true over the last 50+ years. The problem is, they degrade in time. Although you’d have a low front end cost, the maintenance will cost you more through the years than an Allan Block retaining wall. This also doesn’t include the possible environmental disposal costs that can be associated with timber retaining walls.

Next, let’s discuss a natural stone-type retaining wall. These can be comprised of limestone, boulders, or other natural rock available in your region. Typically, natural stone is one of the most expensive options, as it isn’t always readily available. It doesn’t install as easily, and may require special equipment due to the size and weight of the material. Allan Block is a cost-effective solution with so many collections and finishes that look like natural stone in modular block, offering a cost advantage.

Lastly, is a traditional, cast-in-place masonry wall. These systems have full reinforced footings with rebar and require formwork typically to complete installation. These walls are expensive, and can drive up the labor cost due to the amount of embedment in northern climates. A ball park cost savings from a cast-in-place retaining wall to an Allan Block system can be roughly 50%. Allan Block provides an avenue to save money and have a wall that looks better.

Now that we know Allan Block is a cost-effective solution for nearly all sites, it really comes down to what collection and color you would like in your backyard. Visit allanblock.com to select a store near you, or call your local dealer for cost and availability.

October 1, 2020

Stairs Without Being Part of a Retaining Wall

I have a friend that asked me about building a new set of stairs from his cabin’s back patio area down to the lake.  His 20-year-old railroad tie steps were basically gone from deterioration.  The grade is not that steep, which makes his treads quit long relative to the 8 inch (20 cm) riser.  He said he was thinking about using wood again, because he did not think Allan Block products could be used for non-retaining wall applications.

Boy, am I sure glade he asked, because he was totally wrong.  The only limitation Allan Block walls have, is based on the creativity of the installer.  If an installer can think it up, then they can build it with Allan Block, and standalone stairs are downright easy.  In my friend’s case, the installer is simply building a series of one-course walls with cap units, over and over again rising up the grade.  He chose to simply fill in behind the caps with a nice crushed rock. 

Another option could have been to pour concrete or lay pavers for a more solid surface, like this similar project.

For more information on stairs using Allan Block, or any other questions related to Allan Block wall design or construction, contact Allan Block at engineering@allanblock.com.

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 allanblock.com 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 allanblock.com.  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.