Technical News

Exclusively for Allan Block Design Professionals

September 2020

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Our Design Professional ABU Online events were created to help you with your retaining wall needs. Our local production and sales partners will be happy to schedule in person training on any topics you see below (call us if you are looking for those individuals) but feel free to use these to help with immediate needs.

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Water Management and AB Walls 3D+Terraces
Thursday 9/17

Complex Composite Structures (CCS) and AB Walls 3D+Terraces
Tuesday 9/22

No-Fines Concrete and AB Walls
Thursday 9/24

Terraces and Global Stability in AB Walls 3D+Terraces
Tuesday 9/29

Above Wall Considerations in AB Walls 3D+Terraces
Thursday 10/1

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Inspiring Project Ideas














In this Issue:

Case Study: Saddlebrook Golf Course

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Saddlebrook Golf Club in Indianapolis, IN was a cornerstone in the neighborhood until it closed in 2015. During its closure, the greens, fairways and grounds were subject to extensive damage, requiring a lot of reconstruction to be done prior to reopening. One such feature was a tunnel that passed below a street and connected the two different sections of the course.

The entrances to the tunnel consisted of old railroad tie timber walls that were in desperate need of repair to make it useable again.

Read about the full design in the case study to see how using a mix of wall designs solved this part of the reconstruction for the new owners.

Retaining Wall up to a tunnel entrance Timber Retaining Wall

Alternate Drainage - Design Considerations

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Water management can easily be the difference between a wall that lasts a lifetime and one that fails catastrophically. Because of this, Allan Block has made it very clear in our Installation Manuals and Best Practices document that proper drainage cannot be overlooked when designing a retaining wall. One of the several ways we convey this message is through our typical design details.

While the standard detail for designing an Allan Block retaining wall shows a heel drain at the back and bottom of the reinforced zone, and also at the bottom of the base, it is becoming more and more common to design the wall with drainage venting through the face of the wall.

Luckily, Allan Block has an Alternate Drainage Detail that covers how to properly design this configuration. This detail features placing a bed of low permeability granular material at and below grade. This includes the base material, behind and in the block cores, and the infill zone, with a toe and heel drain on top of the material. These drains can then be vented to daylight through the face of the wall and safely away from the structure. Using low permeability granular material for the bed is very important, because we do not want any water migrating past the toe and heel drains.

Alternate Retaining Wall Drainage Detail

Click to enlarge

When venting the drainage pipes through the face of the retaining wall, there are a few convenient options that will make the process easy with aesthetically pleasing results. The first option is to cut either one or two blocks at grade in order to allow the drainage pipe to recess out the face of the wall. While this method does require cutting block, it is still a relatively easy way to allow venting at grade. Another option that is even easier is to use a handy product called Wall Drain Pro.

Wall Drain Pro is a great-looking, non-Allan Block product that allows you to place a vented slot in between two of your retaining wall blocks. The vented slot face connects to a channel that attaches right to the drainage pipe within your wall structure. The slot fits perfectly between blocks, so there is no need for cutting, and it is even manufactured at the same height as an Allan Block Classic unit. The Wall Drain Pro vented face can even be cut in order to fit perfectly into walls that are built using our half-height units. It also comes in a variety of colors to match the blend that your customer is looking for.

So, while Wall Drain Pro is not an Allan Block product, we love to recommend the system to any of our designers and installers using the Alternate Drainage option with an Allan Block Wall. When used together, the Alternate Drainage Detail and Wall Drain Pro provides a great water management solution that is easy for installers to use without sacrificing the aesthetics of the retaining wall for your customer.

Wall Drain Pro Wall Drain Pro

Wall Penetrations through a Retaining Wall

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As we saw in the retaining wall project at the Saddlebrook Golf Club, it is possible to have penetrations through a retaining wall. In fact, one of the benefits of using an Allan Block system is how flexible it can be to accommodate site conditions. These penetrations come in all shapes and sizes, but we know that any type of opening must do two things:

Wall drainage Drawing

Figure 1

  1. Be sized appropriately for the intended use, whether that is a simple drainpipe or a large culvert allowing pedestrian traffic access.
  2. Provide support for the surrounding wall structure to minimize movement and provide the stability the Allan Block retaining walls are known for.

Smaller penetrations like drainpipes can be made without additional support and simply require cutting the block to accommodate the pipe (Figure 2). Please follow the OSHA requirements when cutting block to limit silica dust generation or use a product like Wall Drain Pro to limit the cuts.

Wall drainage

Figure 2

Wall drainage

Figure 3

However, larger penetrations will require additional support. For these openings, stability can be maintained by building supporting bond beams directly into the wall facing (Figure 1) or by a fully reinforced concrete headwall for larger openings (Figure 3).

The real key is to concentrate on proper compaction in and around the opening. Any utility line is notorious for having settlement around it and that is because they do not properly compact when the pipe is installed. Use more rock in these areas if there is a concern that compaction efforts will damage the pipe. This is always a good idea anytime the pipe will be carrying water. Using additional wall rock around the pipe will aid in compaction and help handle any water if the pipe does leak.

For more information on wall penetrations you can review a previous article, give the engineering department a call at 800-899-5308 ext. 3 or email us at

Proper Drainage for Terraces and Site Low Points

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As you have seen in this newsletter, It has become common practice to have the heel and toe drains exit to daylight at grade of a wall using the Alternate Drain. However, there are two scenarios, Terraces and Low Points, that will require other considerations and the “why” behind them:


  • Toe and heel drains shall be routed so they do not exit on the lower terraces.
  • Drainpipes shall be extended to provide a path for water to be channeled away from the wall structure or out through the lower wall face.
    • The images on the right show contractors elevating a drainage pipe, that exits out the face of the lower structure, that will be used in the upper wall.
  • Pipes at exit locations shall be marked to facilitate identification of where water is draining from.


The reason the heel and toe drains should not exit out the face of the upper terraces, is to limit the amount of water that can be introduced into the system. Segmental Retaining Walls are designed under the assumption of a dry infill zone. Once water is introduced, additional loading and pressure is applied that was not accounted for in standard designs.

wall construction with drainage pipe

wall construction with drainage pipe

Low points adjacent to other structures:

  • Toe and heel drains should be routed to an underground drainage system.


The reason we do not want to see the drains exit out the face is to prevent excess water being introduced to areas of potential damage through flooding. As seen in the Saddlebrook Golf course project Case Study above, the lowest point in the terraced structure is right next to the entrance/exit of the tunnel. Therefore the design uses an underground drainage system.

Wing Wall Abutments

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Retaining walls are a fundamental feature for leveling a site. Most of the time, they will start and stop by sloping with the grade below to end at a minimal wall height. However, what about when we are designing a wall to end in an abutment to an existing structure?

For abutting into an existing structure, Allan Block’s multiple collections and modular sizes of blocks offer a few options. By simply cutting a full-sized AB Classic to size where it meets up with the abutment is one option. If the wall is being built on running bond, an AB Jumbo Jr block, which is half the width of the AB Classic, is another option.

Wing Wall with Allan Block

When installing the Allan Block units, it is key to properly excavate behind your wall. This is no different when abutting into an existing foundation wall or side of an existing culvert as in the case of the Saddlebrook Golf Course project. You will need to excavate next to the existing structure to ensure there is proper room for grid embedment for your new wing wall. During installation of the abutting units, it is common to see a layer of filter fabric used as a barrier between the existing and new structures. This layer of filter fabric is not deemed necessary for an Allan Block wall, but can help to limit or eliminate any spill of infill material between the wall and culvert joint. The layer is to be placed directly behind the Allan Block units and runs vertically alongside the existing structure. Expansion foam or similar materials can be used as well, but again are not necessary in most cases.

Wing Wall with Allan Block top view

For more information on wing walls and abutments, reach out to Allan Block engineering department at 800-899-5309 ext.3 or send an inquiry to Also check out our Designer Resources Portal that is accessible from for additional AB resources.

Design Professional Spotlight - Brian Luoma (and Matt Norris) – Geotechnical Laboratories, Inc.

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With engineers all over the world designing Allan Block retaining walls, it takes a lot to be considered one of the best AB designers. In this quarter’s designer spotlight, we’re traveling out to the east coast to showcase a firm that fits that description perfectly – Geotechnical Laboratories, Inc. Matt Norris (the owner of the company) and their main segmental retaining wall designer, Brian Luoma are prime examples of what we love to see in designing engineers.

Aztec Terraces

If an Allan Block project goes through the Geotechnical Laboratories office, it will almost certainly find a place at Brian Luoma’s desk. Brian graduated in 2004 from the University of Maryland with a bachelor’s degree in Civil Engineering. The day before his graduation, he was contacted by Matt Norris to interview at the company. Brian got the job and has been an integral part of the company since. The company offers services ranging from settlement analysis to wall inspection, and everything geotechnically related in between.

Brian has been designing Allan Block for a long time, and some of his earliest experiences with the product come from our production partner, Nitterhouse Masonry Products, sending projects his way. If he ever had any questions, he would be sure to always consult Allan Block’s Best Practices document, and take full advantage of the services the engineering department at Allan Block has provided. This includes anything from specific design questions to attending various Allan Block University Online webinars when he has some free time.

Another Allan Block resource that Brian uses frequently, is the AB Walls design software. He likes when the walls he designs are specified Allan Block, because the software makes it easy to provide elevation, plan, panel, and cross-section views right from the software. Geotechnical Laboratories even uses the built-in print function in AB Walls. This automatically draws out a professionally formatted retaining wall design packet, with their signatures, logo, and stamps included on the border. On top of the conveniences that AB Walls brings to the table, Brian also really appreciates the fact that no-fines-concrete design is built right into the software. This feature has made a lot of close quarter retaining wall designs possible where there would not be enough space for geogrid.

One of the best pieces of advice Brian believes every engineer could benefit from is that you have to know what you are doing before you begin any project. He believes you need to learn as much as you can so that you can put all of the knowledge you gain into practice. It is this type of mentality that makes Brian Luoma one of the best Allan Block designers out there. He understands what it means to be Always Better, and he exemplifies what we would love to see in all of our engineers. Allan Block thanks Brian and the rest of Geotechnical Laboratories, Inc. for all the amazing work they do and the reputation they build for Allan Block. We look forward to seeing many more designs come through their office and can’t wait to see their walls move from a design to being installed.

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