Orientation Of 4x6 Posts In Retaining Wall - Landscaping & Lawn Care - DIY Chatroom Home Improvement Forum

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Landscaping & Lawn Care


Thread Tools Display Modes
Old 07-05-2012, 04:51 PM   #1
Join Date: Jul 2012
Posts: 2
Rewards Points: 10

orientation of 4x6 posts in retaining wall

I am building a 20 foot, 3 foot high retaining wall. I will be using 4x6 posts and 2x12s. I have a simple question - which side of the 4x6 should be parallel to the 2x12 - the 3.5" side or the 5.5" side. I have seen it done both ways.




tomtery is offline   Reply With Quote
Old 07-05-2012, 05:06 PM   #2
PE Mechanical Engineer
Thunder Chicken's Avatar
Join Date: May 2011
Location: Massachusetts, USA, Zone 6A
Posts: 622
Rewards Points: 844

I'd put the short span parallel to the 2' by 12's. Generally you want to put the deepest dimension of the beam in the direction of the load that you want to support.

Having said that, 3 ft is a lot of soil to hold back, especially after a rain. I'm not sure what your plan is but 2 by 12 sounds a bit thin. Have you thought about using ties with deadmen to form the wall? It's a pretty common and strong method to build short retaining walls.


Thunder Chicken is offline   Reply With Quote
Old 07-05-2012, 05:59 PM   #3
Join Date: Nov 2011
Location: Hartfield VA
Posts: 34,419
Rewards Points: 13,968

2 X 12's are not below ground rated. Read the tag right on the lumber.
You would be a whole lot better off with at least 4 X 6's 6 X 6's would be even better.
I would not use railroad ties, the reason is there to short so there's going to be lots of seams, they were removed in the first place because they were nearing the end of there expected life span.
Without a drainage system, using rebar or long spikes, off setting each row, tie backs, silt screen and the support beams at least 4' in the ground your plans not going to work.
joecaption is offline   Reply With Quote
Old 07-05-2012, 07:10 PM   #4
Join Date: Jul 2012
Posts: 2
Rewards Points: 10

thanks for the responses. I didn't give all the details - at maximum the wall is 3 feet, but quickly tapers to 1.5 feet - the wall is at the edge of a small hill, and is actually two walls at right angles. i plan to sink the posts 4 feet into the ground, have drainage pipe, gravel, and geotex against the wall, and compact the fill in layers.

i live in california and have had two contractors bid the job. both spec'd 2x12's, and i have had a 2x12 wall on the property for 10+ years now with no apparent degradation. however your comments are worthwhile, and i will now investigate using 4x6 timbers. thanks!

tomtery is offline   Reply With Quote
Old 07-05-2012, 08:34 PM   #5
Civil Engineer
Join Date: Mar 2009
Location: Boston
Posts: 5,637
Rewards Points: 4,854

You may want to consider building the wall using concrete segmental block. In my experience, it is often less expensive than wood, it lasts essentially forever if properly installed, and you can get a wide variety of block types that look very nice.
Daniel Holzman is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Retaining wall combining concrete blocks and PT lumber JEL Landscaping & Lawn Care 1 04-06-2012 08:39 PM
Retaining wall problem FMS Landscaping & Lawn Care 6 07-04-2011 06:42 PM
Retaining Wall Weeping Tile Problem cg3459 Landscaping & Lawn Care 3 06-16-2010 06:22 PM
Attaching fence post to side of retaining wall? Drew328i Landscaping & Lawn Care 5 06-01-2010 07:53 AM
Drainage Tile and Retaining Wall nabz Landscaping & Lawn Care 3 05-25-2009 01:22 PM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1