Wood Retaining Walls

[Soundguy]

In florida, I've built and seen retaining walls made of timber, both PT and creosote railroad timbers.

One of the largest I've seen was a 20' tall terraced wall of railroad creosote timbers. 8x8's were used as verticle members, and sunk as a friction pile. Has held for years, with no creep. Has flowers, junipers, and crepe myrtle's , and red top as shubs and folage. It is a comercial site, so the well is tested every 3 months by dept. of health ( required by law for a drinking water permit here in florida ).. always tests out good. Rebar sections are used as joiners.

Chris

 

[Soundguy]

As for PT, there is also an Arsenic free version available.. Home depot caries it. Most of the studies I've seen on the CCA products, involve PT wood on playgrounds at public schools, and parks. Probably more of a preventative than anything.. especially since we arbitrarily change the 'safe' level of arsenic in drinking water every time we get a new president.. etc.

As for the retaining wall... I ommitted in my previous post that the person would do well to to get local engineering help. I'm in Civil Eng. here in florida, and most of the big projects need certification. Certain ag projects can get by without it... just depends.... for the price / vs. safety.. it is probably worth investigating it anyway.

Chris

 

[ljh2]

With lights.

 

[wasabi]

Larry's pic looks about like what we are doing. We have a hill behind the workshop that has encroached over time...threatening to rearrange the architecture of the shop! We're digging out about eight feet into the hill, tapering it back and building a 150 ft x 8 ft high wall using locust posts sawwed flat on one side and spiked with 2x10 treated planks. Figure the posts will be about 12 ft long sunk into the earth 4 ft about 5 ft apart. We'll use deadmen and also a shed roof (wood drying and storage sheds). That way the roof joists and front posts with diagonal bracing will help keep the whole affair stout. Also, instead of backfilling, we plan to let nature take its course as regards soil filtering down. From all I've heard it appears the biggest concern is moisture, so we'll use, as so many here suggest, gravel and drain tile to vacate runoff.

 

[Darren]

Another factor not well known is that clay is one of the biggest killers of retaining walls.

Clay soil will put the greatest pressure on a retaining wal of any of the possible backfill materials. Don't use clay for backfill material period. It may take twenty years or it may take one hundred years but clay will cause the wall to move. To aid drainage behind a wall, use geotextile to line the excavation behind the wall. With RR ties, you won't need holes drilled to allow water to escape. Backfill the excavation lined with geo with sand. Compact the sand as you place it. As you get near the top fold the geo over the top of the sand and fill the remaining 8" or so with soil.

The geo will stop fine material from infiltrating the sand and blocking it from passing water readily. In esence you're constructing a french drain behind the wall.

 

[pajoube]

Really like what you did with the retaining wall. Couple of questions, did you put some type of draining materials (rock, pipe, etc) on the outside of the retaining wall?
When completed are you leaving the floor dirt or cementing?
PJ