Understanding Segmental Retaining Wall Systems


By Tony Catanzaro


Segmental Retaining Walls (SRW) are probably the most popular type of retaining wall being utilized today. You won’t have to look far for an example of an SRW. They are what are commonly referred to as “interlocking concrete block walls”. There are many different manufacturers and countless styles and colors.


There are basically two types of SRWs . The first type is the gravity wall. A gravity walls basically stands on its own, with the help of some basic steps, due to the weight of the blocks themselves and the compacted soil behind the wall. The other is a reinforced wall. Reinforced walls utilize the addition of a grid like material that helps anchor and support larger walls and walls with heavy surcharges. Reinforced walls are usually designed and sealed by an engineering firm and then installed by a professional company.


A very common problem is that many walls that should have been built as reinforced walls were built as gravity walls. This can create a dangerous situation. A good rule of thumb is any wall system that has no batter or setback built into it can be used for up to a two foot high gravity wall. A wall system that has a batter or setback can usually be used for up to a three to four foot high wall. Of course check with the SRW manufacturer before constructing as well as your municipality for any permit and code issues.


Soils are very important when it comes to designing and building a successful SRW project. Poorly drained clay soils will require a different design than loam or sandy soils. Most SRW manufacturers have installation guides that will provide basic information and for larger walls an engineering firm may be needed.


Proper base preparation is necessary for the SRW to perform correctly without settling and shifting. Most SRW systems will require one course buried on a six inch quarry process compacted base. Your base course (first row of blocks) must be leveled perfectly both side to side and front to back. It is best to work from the lowest point and “step up” to the highest point. Be sure to correctly calculate your final height so the top course ends up just where you want it.


Install the SRW with a perforated drain pipe along the back of the base course. Ensure an exit point at the lowest end. Use a soils filter fabric to separate the three quarter inch aggregate you backfill behind the block and the soil. Make sure to compact any back filled materials as you build up.


If you are going to build the SRW in terraces there is another rule of thumb to keep in mind.  That is that If the lower wall is “H”, the height of the upper wall should be less than or equal to H. And, the upper wall must be built at a distance away from the lower wall of at least 2 H. For example, if the lower wall is 2 feet high, the upper wall must be no higher than 2 feet, and built at least 4 feet behind it. This is another key point that could cause failure and more so in clay soils.

An SRW project will require some specialized tools to work efficiently and safely. Basic hand tools, masonry chisels, level and other basic construction/landscaping items. Further more; you may need a laser level, demolition chop saw, guillotine for cutting the block, back hoe/excavator, front end loader, compaction equipment and many other specialized tools. In most cases you may want to consider contracting a professional to install your SRW unless it is a small project or you are willing to rent the correct tools and invest your time and backbone into your project.

As you plan your outdoor spring projects an SRW may be part of your needs. They offer a very versatile way to retain soils and create needed level spaces. There colors often match or complement paving stones made by the same manufacturer. As always try to make it part of an integrated site plan for your property to ensure continuity with the rest of your landscape.

Regency Landscape can help you design and install your SRW project! Call today!

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