Retaining Walls That Last – Portsmouth Daily Times
Far too many retaining wall projects start with this simple step: homeowners see a sale of retaining wall blocks, guess exactly how many they need, and have the big store deliver them. Once the block pallets are stacked in the yard, put them aside for a weekend or two, recruit friends or family, and carry out a construction project.
We can easily understand the “do-it-yourself” energy (we call it “the energy of the innocent”) because on home improvement projects we have often gone over our heads when we should have sought expert assistance. By the time the project is finally done, we’ve made enough mistakes to learn how to get it right next time. As we like to say, “Anything worth doing is worth doing twice.”
Building decorative garden walls is very satisfying and rewarding, as well as good practice. If the purpose of the wall is more functional, it is important to add a construction step before starting the project. Retaining walls for the purpose of restraining hills, supporting paving stones or buildings, and controlling runoff are serious projects with long-term consequences. Therefore, “learning by doing” is not always a good idea.
As a certified hardscape builder, we are often called out to the fact that structural retaining walls fail for one reason or another. This is never a pleasant experience for us or the homeowner. It is far more expensive and time consuming to repair a poorly installed retaining wall than it is to install it at all. Usually the cause of the wall failure is provided and the only solution is to remove it and start over.
In the previous columns we offered retaining wall tips. Here is a quick recap of the basic principles we talked about earlier:
Hardscapes should never be built on filler material or on a floor that remains wet due to improper drainage. The center of gravity of a retaining wall should be behind the wall foundation or footer. The higher the wall, the more it should start underground. The heavier the wall, the stronger the footer must be. There needs to be a way for water to freely escape from the footer ditch and behind the wall by gravity. The backfill behind the wall should be neatly crushed (not round) stone.
Walls should be tied back into the mound so the weight of the backfill will keep the wall from moving. Geotextiles are a typical method; A layer of “geogrid” should return into the mound every two passages on higher walls. Water drainage behind the wall must never run into the backfill behind the wall. Curved walls or walls with multiple corners are considerably thicker than long straight walls.
Understanding these basics is a good place to start, but there are many more tips and tricks associated with training and experience. Every wall situation is different, and there are many different types of segment wall systems, each with cost-benefit tradeoffs. We want you to be successful in every home improvement project you dream of. It is important that you know your own limits before you begin.
Usually the cause of the retaining wall failure is provided and the only solution is to remove it and start over.
Steve Böhme is a landscape architect / installer who specializes in landscape remodeling. “Let’s Grow” appears weekly; Column archives are online at www.goodseedfarm.com. For more information, contact GoodSeed Farm Landscapes at (937) 587-7021.