×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Wood retaining wall
2

Wood retaining wall

Wood retaining wall

(OP)
Hello all. Stumbled on this forum, hope someone can help.
Going to build a retaining wall with 6x6 lumber. It will be approx 8' high and it's on the side of a slope.
Looking for the best way to do this. Thought of splitting it into 2 4' sections.
The second section pretty much resting on a 6x6 coming out of the first section.
Also thought that in addition to the sleepers/deadmen, using a geotextile (see yellow in picture) sandwiched
onto the back of the wall and then run within the backfill. The geotextile isn't cheap, so I'm not sure if this
will even serve a purpose.

RE: Wood retaining wall

(OP)
I do want to mention that in my picture, I have used what appear to be 12"x12" logs! They are 6x6, so there aren't enough depicted :)

RE: Wood retaining wall

That looks like an unplanned failure. It is an all too common way out of trying to build a high wall by using set-back distances that are not sufficient and very little anchorage back into stable soil. - The entire "structure" is just asking to slide down the slope.

I think a good engineer and a little soil sampling will give you something that would be legal and approved.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

RE: Wood retaining wall

My first choice would be a segmental retaining wall (precast block system) such as Keystone, Allan Block, Versa Lock, Anchor, etc.

EIT
www.HowToEngineer.com

RE: Wood retaining wall

Provide more data. What type of soil is in that slope? What is the backfill proposed? Any water present in that bank? What purpose for the wall? What will sit on top?

Off hand, the only geotech layer you show that would appear to have some merit is the top layers and even then maybe too short.

If that drawing is to scale, I see the slope at 30 degrees to the horizontal, which is just "safe" for loose sand. Adding any wall is likely to fail, with that assumption..

RE: Wood retaining wall

In addition, fill should not be placed on that existing slope without some horizontal benching to prevent the fill from sliding down.

www.PeirceEngineering.com

RE: Wood retaining wall

2

If it were me, I would NOT do a timber wall. I have a 20+ year old wall that has deteriorated almost to ground level on the face side. Simply put, wood will rot over time, no matter what kind of "preservative" is used. What kind of problems will you leave the next owner?

If nothing else, use a segmental precast wall with properly designed geotextile grid holding it in place. It is more than worth the investment in the long run.

Timber walls are good only for low height landscape features that can easily (relatively speaking) be replaced in future years.

Just MHO.

Ralph
Structures Consulting
Northeast USA

RE: Wood retaining wall

Ralph....exactly!

RE: Wood retaining wall

an 8 foot high retaining wall will almost certainly require a permit. have you run this idea past your building dept yet?

RE: Wood retaining wall

Well, if you are in a dry environment, which I am not mind you, a wood wall could work for 30 years or better. Mine, 5 feet high, has held for 30 years, but is of much different construction than you show.

I used 4X6 PT posts at 5 foot centers embedded 2 feet into cementious sand (an 8" power auger would hardly touch it), sll in a concrete filled hole, then spanned PT 2X6's on the backside for a temporary wall. The next year I came back and strung some horizontal and vertical rebar between the posts and infilled with a 5.5" thick concrete wall, with a small 2 foot toe formed into my driveway (do you think that helped?). The posts are retaining some soil load from the concrete wall, but not all of it by any means. After 30 years, the posts are are still structurally sound though.

I would definitely step the wall, regardless what solution you use. If you decide to use pole footings, you will need to go deeper due to the downslope.

Mike McCann, PE, SE


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources