How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manfuactured and modular homes
What are the most common causes of retaining wall failure?
Thursday, May 26, 2022
The most common cause of residential retaining wall failure is inadequate structural design. As the height increases incrementally, the force exerted on a retaining wall by the soil behind it grows geometrically. So doubling the height of a three-foot foot wall to six-feet quadruples the pressure on the wall and requires a much sturdier wall design. Also, the type of soil—whether it’s sand or clay, for example—affects the calculations for the structural design. Failure is usually not an abrupt, dramatic event, but happens slowly over several years.
Not providing adequate drainage is the second most common cause of failure. Without a drainage system, buildup of water behind the wall begins to liquefy the soil, which makes the pressure jump higher during wet weather.
Lack of maintenance is third on the list. Rusted reinforcing steel inside a poured concrete retaining wall causes cracks that will continue to open further unless repaired. Wood retaining walls require replacement of rotten areas as the wall gets close to the end of its lifespan. And stacked stone walls can start to drain soil from openings between the stone over time, which need to be closed as they appear.
It’s a good idea to take a careful look at your retaining every year or so, specifically sighting down the length of the wall while standing close to it, looking for any bulges or leaning. Some local governments even require regular professional inspection and certification of tall retaining walls that face a public right-of-way, like in the photo below, because collapse would cause damage and possible loss of life.
Also see our articles How do I recognize structural problems in a retaining wall? and Should I buy a house with a retaining wall?
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Here’s links to a collection of our other blog posts about a home’s SITE:
• Which trees are most likely to fall over on your house in a hurricane?
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