Retaining Wall Installation - Best Practice

By
Home Inspector with Jay Markanich Real Estate Inspections, LLC

It's time for a post about retaining wall installation - best practice.  Retaining walls are something that home inspectors see frequently.  And just as frequently those walls have problems.

A recent post prompted many to think what is necessary to the proper installation of a retaining wall.  This is a very good question, and one deserving a response.

Retaining walls can be constructed of many things - metal, wood, brick and block, man-made blocks, and huge boulders and stone.  The idea is to retain the weight of the soil behind the wall, and divert water, and its pressure, away from a structure or pathway.

An engineer I have known and referred for many years is Ken Fraine, of Soil and Structure Consulting, Inc.  When asking him his thoughts regarding this post, he said,

"Nearly every failed retaining wall I’ve ever inspected failed due to an improper drainage system or a complete lack of one.  Note that [concrete] block walls should also have a waterproofing membrane placed on the backside to prevent deterioration of the mortar joints and the blocks themselves."

Drainage, therefore, is significant.  The the single-most reason walls will eventually fail.

Properly constructed, retaining walls are very complex.  Many things work together to insure their success, from retaining wall material, back fill, angle of the wall setback, stabilization into the rear structure and drainage, etc..

I have seen retaining walls made from the man-made blocks that are 30' high and more.  Of course, with that height, more drainage is necessary than the single collection pipe shown here.  Those blocks intersect, or have lips which rest on each other such that one cannot be moved as regards its neighboring blocks.

The collection pipe would be a 4" plastic tube with pre-drilled holes to collect and then divert water.  Of course it would be wrapped with a silt-filtering mesh and then protected with gravel (called Unit Core Fill/Drainage above).

Even with different wall materials, the components shown above would still apply.  And any wall constructed like the one in the diagram above would be

Best Practice

My recommendation:  just from a visual inspection or walk around, it might be difficult to determine if a retaining wall has all the components and structural capability of the diagram above.  But you can ask!  Find out who did the work, try to obtain any permits and receipts and investigate the company that put the wall in.  Doing all that will go a long way toward the peace of mind needed to know if a wall will last.



Posted by

Jay Markanich Real Estate Inspections, LLC  

Based in Bristow, serving all of Northern Virginia.

Office (703) 330-6388   Cell (703) 585-7560

www.jaymarinspect.com


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Re-Bloggged 8 times:

Re-Blogged By Re-Blogged At
  1. Cal Yoder 12/29/2011 10:04 AM
  2. James Lyon 12/29/2011 12:17 PM
  3. JO SOSS 12/29/2011 12:37 PM
  4. Chris Smith 12/29/2011 01:58 PM
  5. Kelly Mac Group (619) 319-7010 San Diego Beach and Luxury Realtors 12/29/2011 04:30 PM
  6. Gene Riemenschneider 12/31/2011 01:00 PM
  7. Sue Ellett 01/01/2012 09:45 AM
  8. Gabe Sanders 01/02/2012 06:18 AM
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Comments 63 New Comment

Rainmaker
1,165,824
Jay Markanich
Home Inspector - servicing all Northern Virginia
Jay Markanich Real Estate Inspections, LLC

John - that sounds like a disaster planned from the start!  Good thing the city got involved.  And you are right, this kind of thing is no day laborer undertaking!

December 31, 2011 07:48 PM
Rainmaker
154,451
Tina Gleisner
Home Tips for Women
Home Tips for Women

Jay, Thanks for the great illustration showing how a retaining wall is supposed to be done. Maybe if homeowners can see this, they'll realize this isn't a simple weekend project and call for help.

February 01, 2012 02:52 PM
Rainmaker
1,165,824
Jay Markanich
Home Inspector - servicing all Northern Virginia
Jay Markanich Real Estate Inspections, LLC

Tina - there are a couple of "retaining walls" I can see from my house that could have used a diagram!  And thanks!

February 01, 2012 05:08 PM
Rainmaker
260,268
Wayne B. Pruner
Tigard Oregon Homes for Sale, Realtor, GRI
Oregon First

Retaining walls built to code around here are very robust. I built one I called "The Iraqi Tank Trap". It was so much over-kill.

October 19, 2012 10:13 AM
Rainmaker
1,165,824
Jay Markanich
Home Inspector - servicing all Northern Virginia
Jay Markanich Real Estate Inspections, LLC

Sounds very cool Wayne!  Would love to see a photo!

October 19, 2012 02:55 PM
Rainmaker
1,165,824

Jay Markanich

Home Inspector - servicing all Northern Virginia
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