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-Blogged 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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Rainmaker
630,004
Stephanie/Bob The Ruiz/Miller Team
Keller Williams Cornerstone Realty - Ocala, FL
The Ocala Dream Team

Hi Jay, thanks for your post.  They are always so educational.

Have a Happy and Prosperous New Year!

December 31, 2011 08:13 AM #44
Rainmaker
1,220,239
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Thanks Bob, and the same backatcha!

December 31, 2011 08:15 AM #45
Anonymous
Anonymous
Anonymous

Hi Jay!  I have to say, I have yet to see a retaining wall on an inspection that isn't showing signs of failure.  I even saw one made of those massive concrete blocks that have to be set in place by a crane (so you know it wasn't DYI), and it was one of the worst.  Unfortunately, the need for drainage seems to be often misunderstood.

December 31, 2011 10:12 AM #46
Rainmaker
347,853
Sylvie Stuart
Keller Williams Check Realty 928-600-2765 - Flagstaff, AZ
Home Buying, Home Selling and Investment - Flagstaff, AZ

You are such a thorough home inspector, which makes you very good at what you do! You always have some new information I didn't know and this was one of them! Thanks for the info!

December 31, 2011 10:15 AM #47
Rainmaker
1,220,239
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

I think you hit on it Julie.  It was probably the lack o' drainage behind that compromised even the biggie retaining wall.

Sylvie - you are very welcome.  Have a happy happy.

December 31, 2011 10:26 AM #48
Rainmaker
711,941
Winston Heverly
Winston Realty, Inc. - Atlantis, FL
GRI, ABR, SFR, CDPE, CIAS, PA

What one has to marvel is in ancient times, building and wall retention that still stands today. This in contrast to the attempts that you come across in your inspections.

December 31, 2011 12:05 PM #49
Rainer
22,149
Alan Mackenthun
Bridge Realty - Shakopee, MN

Great article.  I did install my own retaining walls 10+ years ago.  Followed all the instructions carefully, except I cut the embedment depth on one side of the house.  It started raining and the whole wall next to the house slid forward a bit.  Water followed it to the foundation wall and followed it around and into the basement :(.  Pulled out the whole thing, dug out the trench another 6" relaid the foundation and reset the whole wall.  Been solid as a rock for 10 years now.  You're certainly right that you can't take short cuts, but a home owner who can and will follow directions can do it right.  Contractors can also be templted to take shortcuts.  It's mostly just hard physical labor.

2 level retaining wall

December 31, 2011 12:06 PM #50
Rainer
376,389
Bill Reddington
Re/max Southern Realty - Destin, FL
Destin Florida Real Estate

Not many retaining walls here in Northern Florida. One less inspection issue to deal with in terms of possible hidden damage. Happy New Year!

December 31, 2011 12:48 PM #51
Rainmaker
1,243,207
Gene Riemenschneider
Home Point Real Estate - Brentwood, CA
Turning Houses into Homes

This is an excellent post.  Thanks for the information.  This is good consumer information that I like to share with clients.

December 31, 2011 12:54 PM #52
Rainmaker
1,220,239
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Winston - there is a lot of ancient stuff, on different continents, that we all need to wonder about!  They had some great engineers!

Alan - you are right about the no short cut thing.  And you are right, drainage is everything.  Obviously you did a great job!

Thanks Bill.  What, things are pretty flat there?

Gene - thank you!  We try to be very instructive!  I am glad it is a sharable post.

December 31, 2011 01:00 PM #53
Rainer
307,049
Jennifer Chiongbian
Specializing in all types of Manhattan apts & townhouses - Manhattan, NY
Real Estate Broker - NYC

Thanks for all that valuable info. Never realised there was so much behind the construction and detail of a retaining wall that needs to be fulfilled in order to last.

December 31, 2011 02:17 PM #54
Rainmaker
1,220,239
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

It's all true Jennifer, and if steps are skipped they don't last!

December 31, 2011 04:20 PM #55
Rainmaker
562,448
Steve, Joel & Steve A. Chain
Chain Real Estate Investments & Mortgage, Steve & Joel Chain - Cottonwood, CA

Jay,

Hydrostatic pressure is a remarkable force. Dewatering is vital to hillside stablity. Many landslides are the product of excessive water pressure. Congratulations on your feature. SC

December 31, 2011 06:13 PM #56
Rainmaker
1,220,239
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Thanks S&J!  I see evidence world wide that water is a remarkable force, for sure.  Have a great new year.

 

 

December 31, 2011 06:25 PM #57
Rainmaker
196,092
John Alesi
Century 21 Award - Mission Viejo, CA
(Orange County California Real Estate)

My neighbor decided to excavate the slope between our yards, leaving an 8 foot vertical dirt wall that he thought would be held back by simply installing those Pavestone overlapping blocks on a dirt base.  No drainage, no footing and definately over the height limit for this type of block. Fortunately, the city stopped the project before the three adjoining neibor's backyards slid into his yard in a massive land slide!  Additionally, there were no permits with the city!

The city made him submit plans created by an engineer requiring the installation of a concrete block wall (with the cells filled with concrete) built on a footing with correct drainage...the proper way to do it!

This type of work should not be left to day laborers with no experience in the correct installation of retaining walls.

December 31, 2011 07:45 PM #58
Rainmaker
1,220,239
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

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 #59
Rainmaker
155,826
Tina Gleisner
Home Tips for Women - Portsmouth, NH
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 #60
Rainmaker
1,220,239
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

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 #61
Rainmaker
261,430
Wayne B. Pruner
Oregon First - Tigard, OR
Tigard Oregon Homes for Sale, Realtor, GRI

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 #62
Rainmaker
1,220,239
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

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

October 19, 2012 02:55 PM #63
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Rainmaker
1,220,239

Jay Markanich

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