post and plank retaining wall

[Smackthis]

Has anyone ever built a post and plank retaining wall? I need to install a 45 foot long by 3.5 foot tall retaining wall. I will be using
6x6's for the post's and 2x12's for the planks. My question is how far apart should the 6x6's be placed? I have been told by different sources every 2 feet, 4 feet or 6 feet apart. This wall is going in a back yard were there is very little traffic and the ground is rocky and dry. Any advice would help. Thanks

Todd

[AGLA]

6" O.C.

Just kidding. I would not build a post and plank retaining wall three and a half feet tall. The physics don't work. It may last a little while, but it will fail.

There is no mechanism at work to hold back that force. Most retaining walls of wood are "gravity walls" which use mass to counter the force of the retention. They either use geotextiles or "deadmen' to tie combine the mass of soil to the wall. You are attempting to hold bak a hill with little more than a well anchored fence.