December 12, 2019

What is the AB Dogbone and What is it Used For?

The AB Dogbone is used to connect the facing units of the AB Fieldstone Collection together.  We call them dog bones because they have the shape of a bone.

Typically, we use them for building parapet walls. There are 2 options for building parapet


Where the AB Dogbones connect the facing units together. Easily build corners and parapets
with posts. Offers the smallest width, for straight walls only.


Where the AB Dogbones act as anchors in the wall rock allowing any size width to be created.
Works well for straight and curved walls.

December 5, 2019

Will Allan Block Retaining Walls Perform Well in High Seismic Zones?

Allan Block Segmental Retaining Walls (SRW) are the only SRW products to be tested in full-scale seismic testing on one of the world’s largest shake tables located in Tsukuba, Japan.  The tests were conducted in the fall of 2002, and were tested at loads that exceeded the 7.2 magnitude of the Kobe, Japan earthquake in January of 1995.  To read more about the tests, see the test report ( ) or the Executive Summary (

The results of the tests performed by researchers from Columbia University, University of Delaware and the Science Institute of Japan were so remarkable that in only 5 short years, all viable design codes in North America accepted the results and modified their seismic design calculations.

The key to the incredible performance of an Allan Block segmental wall under seismic loading, is the flexible nature of the system and the remarkable facial strength and stability of the facing.  The blocks are assembled with no need for the mortar that concrete masonry block walls require, and have a virtually continuous connection to the horizontal geogrid layers. For more information on geogrid reinforcement, see our website: .  The reinforced soil mass faced with Allan Block easily handles the seismic events by its ability to flex and move with the seismic waves, while remaining fully intact and stable.  For more on seismic loading and design consideration, see the Best Practices for Segmental Retaining Wall Design.

                                       Allan Block Retaining Wall Seismic Test Video

November 28, 2019

What Type of Equipment is Needed to Build a Concrete Fence?

Let’s face it, having the right tool makes every project easier.  This is no exception when building an AB Fence.  You will be digging holes for footings, moving dirt and block, compacting dirt, mixing concrete and even cutting concrete block.  The list of tools that is starting to go through your head should be quite long.  

Most contractors will have most of these tools already and even the above average DIYer will have a good start on this list.  However, the ones that will make this job easier are the power tools consisting of a Bobcat with an 24-inch auger attachment used to drill the footings, a laser level to locate proper elevation and a concrete vibrator used to consolidate the concrete and ensure stability.  Obviously, you may be cutting block so having a saw with a diamond blade is very important.

Constructing an AB Fence is not difficult, but I would recommend an experienced DIYer or hiring a certified contractor to tackle the job. 

November 21, 2019

How Do I Figure Out How Many AB Fence Blocks I Need?

Any good handyman or Do-It-Yourselfer knows that you need proper tools when you want a job well done.  That is why Allan Block has an estimating tool that can be downloaded at or click on this link (AB Estimating Tool For Retaining Walls, Patio Walls & Fences). 

To get started on your estimation, you need to deliberate the final aesthetics of the project. Here are some things to consider:

Standard Block Fence with Iron Fencing Above
  • What is the height of the fence?
  • What is the overall length?
  • Are there corners or openings that need to be considered?
  • Will you be finishing the posts one block higher than the panels as we recommend, or even taller to account for iron or metal fencing?
  • Are you constructing an Ashlar Pattern panel, or just using Standard Panel Block? 

Ashlar Pattern Panel

Once you have answers to these questions, you can use the AB Estimating Tool and get the amount of block you need.  Obviously, there are always people to help you.  Click on “Find a Store” at and talk to your local manufacturer for any questions you may have.  Or send us an email at

November 14, 2019

When Building a Fence, Does the Spacing of the Posts Really Matter?

The short answer is “Yes”.  The post spacing of the AB Fence is critical when you consider the stability of the system.  Let’s draw on a comparison like when you were a kid and you stuck your hand out the window of a moving vehicle. Now some of us never grow up and I continue to do this as I fight traffic. 

When you have your hand is pointed forward you feel very little wind resistance.  However, the moment you raise your hand up you feel all the wind pressure trying to push your arm back.  When you are changing the position of your hand you are changing the tributary area the wind can hit. 

This is the same thing for the panel length.  The longer the panel length the more area of the fence the wind can hit and each post needs to resist that pressure.  If this pressure is to great then the spacing will need to be reduced.  This is one of the key design elements when engineering the AB Fence.
There are other things to consider besides the stability.  This includes grade transitions along the fence.  It is easier to step the fence up and down at a post location.  On steep transitions the easiest thing to do is decrease your post spacing. 

For more information on post spacing, as well as other important aspects of design, please reference our Installation Manual for Allan Block fence.

November 7, 2019

What is AB Fence?

AB Fence is a mortarless concrete masonry fence system that uses maintenance-free interlocking blocks to create an attractive and effective solution for sound abatement, security, privacy and more. AB Fence has a clean, crisp architectural look and comes in many colors that will compliment any new or existing site.

This versatile fence system has been built to heights exceeding 30 ft (9.1m) tall and in areas subject to hurricane force winds.  It is a fully engineered system that can be used to enhance any property.  It has been used for all types of projects including residential, commercial and government owned projects. 
The main structural element is the steel reinforced post.  Typically, the post is constructed on a drilled shaft concrete footing, but can easily be constructed on top of other types of foundations, or even atop reinforced concrete walls or above Allan Block Segmental Retaining Walls (SRW).

For more information on AB Fence, please contact the Allan Block Engineering Department at or see our AB Fence home page on our website:

October 31, 2019

Can a Concrete Leveling Pad be Used for an Allan Block Wall?

Engineers and installers often wonder whether a concrete leveling pad may be superior to gravel.  While a rigid foundation isn’t what we’d typically recommend, it can be used provided the engineer okays it.  Unlike gravel, however, this footing may crack and break apart as the wall shifts with moisture and temperature changes.  Concrete will also be more expensive and typically add to labor, so it should be avoided in most applications.  If an existing concrete footing must be used, then the bottom course of block must be tied to the footing using steel rods.  This eliminates concerns of potential sliding of the wall.

Most Allan Block walls are designed with a gravel base which is a minimum of 6 inches in depth, and 2 feet in width (15cm and 60cm).  There are benefits to using this type of footing.  One major benefit in cold climates is that gravel is not negatively impacted by movement caused by freeze-thaw.  To learn more about our recommended base, visit the base installation guide.

October 24, 2019

What Kind of Material do I Use to Fill the Blocks & the Drainage Behind the Blocks?

A long lasting and great looking retaining wall project begins by selecting the proper material to use during construction of the wall.  After you have selected the proper block to use, you may find yourself wondering “what do I put within and behind the blocks?”
Typical Section
Wall Rock
To build a quality wall, use a clean, granular rock (to a depth of at least 12” (30.5cm) behind the block) to ensure better drainage and compaction to improve the overall performance of your finished wall.  We refer to the material used within and behind the block as Wall Rock. Crushed or smooth stone, well graded, compactable aggregate, ranging in size from 0.25 in. to 1.5 in. (6 to 38 mm) is the ideal wall rock size.  Your AB Dealer will most likely have what you need.
For complete installation details, check out our installation guides.

October 17, 2019

How Does Geogrid Work on Curves and Corners?

If you are building a reinforced retaining wall, there is a good chance you will have either curves or corners in your design.  How do you maintain the reinforced soil when building curves or corners? 

When building curves, the geogrid reinforcement needs to cover 100% of the curve. If it is an inside curve, the grid will be placed around the curve with gaps in between - the gaps will be filled in with grid on the next course.

For outside curves, the grid will be placed all on the same course, overlapping in the curve.  Wall rock will need to be added between the overlapping portions of the grid, so the pieces of grid don’t rub together.

For inside corners, the reinforcement grid needs to extend past the corner in each direction on alternate courses for stability the corner. 

For outside corners, the grid is simply rolled out along the wall in one direction on one course and in the other direction on the next.  While the concepts are pretty simple you will want to make sure you install correctly as corners are usually the most susceptible to sagging or wall failure. Best Practices for Segmental Retaining Walls gives detailed information on how to handle proper gridding of corners and curves.

 To be sure you get it down just right – read all about it in the Allan Block Installation Guide.

October 10, 2019

What do I need to know as I plan/design my retaining wall?

There is a lot of planning that goes into a retaining wall design when things begin to start moving forward.  To provide more information, you can visit the Allan Block Residential Retaining Wall Manual to help organize and formulate your plan. To summarize some of the main talking points, lets break it down into the following 5 items:

           Soils – What type of soils do you have at your project?  Are they sandy? Clay? Gravel?  This can increase the pressure on the wall, and require additional reinforcement depending on the height of your wall.  Since the purpose of the wall is to retain soil, this remains one of the most important aspects in the design.

           Slopes – Are there slopes above the retaining wall?  If the grade is going to slope above the wall, this is an added load and therefore may also require additional reinforcement.  Slopes above a retaining wall remain one of the largest loads possible; the steeper the slope, the more load the wall will carry.  What about slopes below the wall?  If there is a slope below the wall, then you will want to verify with your local engineer that global stability isn’t a concern, or that your wall will remain stable.  Slopes above and below a wall are an immediate red flag for a global stability concern.

          Surcharges – A surcharge can be anything above the wall that adds weight to the soil behind it.  This can be a parking lot, a driveway, a building, equipment, snow loads, or as mentioned above, slopes.  Anything that may be placed above the wall with a sizable mass to it is considered a surcharge.

      Water Management – Water is the #1 reason why walls fail.  With that being said, you will want to make sure your grades around the retaining wall don’t bring water towards it.  Instead, you’ll want to use berms and swales to guide water around the wall, keeping the soil behind it as dry as possible.

Examples of permeability in different soils and gravel.

      Retained Height – The height of the wall plays a major role.  As the height increases, more pressure is exerted on the wall.  Many local building codes govern when a retaining wall needs engineering and permitting, but even small walls can have issues if the previous notes aren’t planned for and taken into consideration.  As the wall increases in height, you will want to make sure you have additional reinforcement to make sure your wall lasts a lifetime!

These items may not be the only items to check and consider prior to construction of your retaining wall, but it is a quick list to run down as you begin to plan your wall project.