Retaining Wall Construction

A structural retaining wall provides stabilization to hillsides and slopes. Segmented retaining walls add usable space, protect your yard from erosion, and compliment the space with added dimension.

Important Retaining Wall Considerations

A true retaining wall is load bearing. Typically, walls more than 3’ tall are considered a retaining wall. Most walls less than 3 feet tall have a different classification in most County jurisdictions. Always check with your local county building permit office for local standards and code.

What is a Segmental Retaining Wall?

The National Concrete and Masonry Association (NCMA) defines a Segmental Retaining Wall (SRW) as an Earth retention wall comprised of dry-stack, modular concrete block units and compacted soil fill with or without the inclusion of soil reinforcement.

The NCMA says there are two types of SRWs:

•Conventional gravity retaining wall

•Geosynthetic reinforced soil retaining wall

Stabilization with Geogrid

Behind the retaining wall is a “reinforcement zone” in the gravel and soil. Geo-Grid is typically used on every other course of wall block to achieve this reinforcement and stabilization.

Greg Naylor, a Structural Engineer at Naylor Structural Engineering, tell us:

"Geogrid works by improving the mechanical properties of the soil mass behind the wall, similar to adding rebar to concrete makes the concrete stronger."

Proper Drainage

Drainage is a primary concern. Improper drainage is a leading cause of retaining wall failure.

Greg Naylor, P.E. commented about drainage: "Water collecting behind a retaining wall can have disastrous effects. To help alleviate these effects, Engineers will specify gravel backfill and drain pipes behind to wall to allow the water to dissipate"

Hydrostatic pressure can quite literally topple a wall down to the ground. Rebuilding a wall that was not properly constructed is costly. And can be even worse when other property is damaged in the process. Not to mention how terrible it would be if someone is injured as a result.

What should the SRW Contractor Provide?

The NCMA also suggests that the wall contractor should not be responsible for the engineering services or quality assurance.

The construction company building the wall needs an installer credential, relevant experience, performance bond, and a minimum warranty.

Installer credentials are typically provided by individual block manufacturing companies. For example, Valley Deck & Patio has found Keystone Compac III to be the best block on the market for SRW construction. Therefore, Valley Deck & Patio has arranged for employee education and holds a installer certificate from Keystone.

Retaining Wall Permits and Engineering

Walls more than 3 feet tall may require a permit. County Codes vary by location. It is always best to check with the local office to verify as guidelines change from time to time. Most of the time a permit application must include an engineers building plans that have been stamped.

A qualified licensed structural engineer needs to be engaged to prepare the appropriate plans.

Valley has worked with many local engineers over the years. We are more than happy to give you a few names of people we have worked with in the past.

The Bottom Line

If you are going to build a retaining wall, build it the right way. The wrong way can cause damage to people and / or property. Experts are here to help. Valley Deck & Patio will make sure your retaining wall is installed correctly.

The Author and Valley Deck & Patio would like to thank Greg Naylor P.E. for adding context and supporting quotes for this article. If you would like to reach Greg, please visit www.naylorstructural.com and request more information. 

You may also visit www.ncma.org for information on retaining wall construction.