The Anatomy of a Retaining Wall

Written by: Danelle DeMartini

A retaining wall is a structure that holds or retains soil behind it. There are many types of materials that can be used to create retaining walls like concrete blocks, poured concrete, treated timbers, rocks or boulders. Some are easy to use, others have a shorter life span, but all can retain soil.

SRW’s (Segmental Retaining Walls) like the Allan Block products, offer concrete masonry blocks that are modular and interlocking for ease of use. Simply stack the mortarless blocks together using our installation information, and create a maintenance-free retaining wall that will add usable land, fix a grading or slope issue, and solve many other site problems. These SRW’s use similar construction techniques as found in the mortarless construction of the Great Wall of China and the Pyramids of Egypt and will stand the test of time. 

The basic parts of a segmental retaining wall, or modular concrete block wall consist of:

Retained Soil:

The area of soil behind a retaining wall that is contained by the wall structure

Infill Soil:

The soil used to backfill behind the wall rock in the reinforced zone. These soils need to be identified and approved by a qualified engineer before they can be used. A granular type of material is best. 

Reinforcement grid:

A manufactured high strength reinforcement grid material that comes in rolls of various sizes and strengths.

Allan Block (segmental retaining wall block - SRW):

Hollow core segmental retaining wall block (SRW) used as the face of the retained soil mass. 

Wall Rock:

Compactible aggregate ranging in size from 0.25 in to 1.5 in. (6 mm to 38 mm) with no more than 10% fines. Used for base material, within block cores and behind the block. 

Drain Pipe:

Used to direct incidental water that makes its way in behind the reinforced mass, and vents it to daylight by creating a channel for the water to flow out from.

Once you build a wall with an SRW – you can be sure it is built to last. For more information on  segmental retaining walls and construction techniques, visit our website at allanblock.com.

Why the Different AB Courtyard Caps, Allan Block?

Written by:  Nate VanBeek

So you’re building your first AB Courtyard project. You have just finished laying the top course of your first wall panel. Now it’s time to start capping your wall. You start placing the caps atop your wall panel and you quickly realize that some of your wall caps are different. They won’t set right because the groove doesn’t go all the way through the block. Now when you place them on top of the raised ring they’re sitting half an inch higher than surrounding blocks. The reason for this is simple; the AB Courtyard wall caps are manufactured with a standard and an end cap finish. 

These finished end caps are great for capping vertical ended walls or step downs. There is an average of 1 end cap for every 4 standard caps when offered by the local manufacturer (check for availability.) There are two ways to install an end cap when it meets up with the raised ring of the block below. 

Option 1: Flip the block below over

• Option 1: When the end caps meets up with a raised ring; flip the block below over to create a flat surface. This will allow the cap to be placed with no modification needed. 

Option 2: Remove notch on end cap

• Option 2: Using a hammer and chisel, break off the notch on the bottom of the cap to allow for proper installation. Once all the caps are installed, secure them in place with a bead of masonry adhesive on both sides of the raised rings.

For more information about how to finish AB Courtyard wall panels with caps take a look at our CappingWall Patios page and for information about all things pertaining to building with AB Courtyard take a look at our AB Courtyard Installation Manual.

Segmental Retaining Walls (SRW) or Cast-in Place - Which is Better?

Written by: Kyle Huerd

For decades, commercial site developments have commonly constructed cast-in-place reinforced concrete walls to retain soil. However, since the mid 1980’s, segmental retaining walls (SRW’s) have provided a better solution to these rigid walls. Some of the advantages SRW’s have over cast-in-place walls include the following:

• Lower installation cost (30-70%)
• Limited excavation for footing preparation since frost depth is not a factor
• Faster installation
• Easier to design
• Better aesthetics
• More reinforcement options (e.g. Geogrid, No-Fines concrete, wall anchors, etc.)
• Flexible vs. rigid system

Aside from all the advantages listed above, what is often missed is the fact that SRW’s can also out-perform rigid walls, particularly in the most aggressive circumstances possible, such as during an earthquake. SRW’s ability to withstand seismic loading conditions has been proven in both the laboratory and the real world.

Allan Block’s full-scale seismic testing documented that SRW’s can withstand large seismic forces. The testing subjected the test walls to forces up to 0.8g and all experienced only minimal deflection and/or settlement. The tests showed the block facing, soil mass and geosynthetic reinforcement all moved together as a unit, in phase with the earthquake induced forces. It was suggested by Dr. Hoe Ling from the Columbia University that these structures, that are both flexible and coherent, are ideal for seismic conditions (ABSeismic Research Summary, Reference Document #R0505, August 2003).

In today's world, with Segmental Retaining Walls being tried and true for more than 30 years, there isn’t much of a market for traditional cast in place walls anymore.  The next time you think you have to use a cast in place wall on a project, just call Allan Block Engineering Department for a second set of eyes to see how we can find the most efficient design.

More Circles! Building tips for AB Courtyard projects

Written by: Nate VanBeek

Everybody loves building circles with AB Courtyard! But, what is the smallest circle that I can build with AB Courtyard? If you build a circle using AB York blocks with the long edge oriented to the outside of the circle it will take twenty-eight blocks to complete a circle.

The circumference of a circle made with AB York blocks exclusively is roughly 81 in. (2.0 m).  to the outside edge. That is the smallest diameter circle that can be built using AB Courtyard without modifying blocks. Our AB Courtyard Fire Pit page has videos, pictures, and step-by-step instructions on how to build this circle.

For more information about building with AB Courtyard refer to our AB Courtyard Walls by Allan Block publication. For more specific guidance building curves check out this page: Howto Build Patio Walls with Curves. We also a page dedicated to building larger curves: How to Build a Large Curved Patio Wall Panel.

The fun doesn’t stop there

With AB Courtyard you can build all sorts of circles. By alternating AB York blocks with the short edge towards the inside of the circle and AB Dublin center split blocks with the long edge oriented towards the inside of the circle, a slightly larger radius is obtained (roughly 96 inches).

Another option for a slightly larger radius (roughly 112 inches) is using one AB York with two AB Dublin center splits. Orient the AB Dublin center splits so that their tapered edges face one another. Follow this with an AB York with its short edge oriented toward the inside of the circle. Repeat this pattern to complete the circle.

 For an even larger radius (roughly 184 inches) use two AB York blocks side-by-side (or one AB Dublin) followed by a AB Dublin center split with its long edge oriented toward the inside of the circle. This pattern is then repeated until the circle is completed. All of these radii are shown in our AB Courtyard Reference Guide.