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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Field Guide for Home Inspectors, a quick reference for finding the age of 154 brands of HVAC systems, water heaters, and electrical panels, plus 210 code standards for site-built and manufactured homes, and the life expectancy rating of 195 home components. Available at amazon.com for $19.95.
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Here’s links to a collection of our other blog posts about a home’s SITE:

• Why do so many more sinkholes open up after a hurricane?

• Should I seal the pavers at my patio and driveway or not? 

• How much is the ground required to slope away from a house? 

• What is a chimney sinkhole? • How do I recognize structural problems in a retaining wall?  

• What are the warning signs of a sinkhole? 

• What causes sinkholes? • How can homebuyers protect themselves against buying a house over a sinkhole?  

• What should I do about a tree with roots running under my house?

• Will the electric company trim branches rubbing against the overhead service lines to my house?

• How can trees damage a house? 

•  What causes cracks in a driveway?

• What is my chance of buying a Florida home over a sinkhole? 

• Which trees are most likely to fall over on your house in a hurricane? 
   Visit our SITE page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.