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I'm looking for a way to build a small retaining wall. I need it to be between 2-3 feet tall and about 30-40 feet long. I'd like to do it as cost effectively as possible. I thought of using pressure treated wood. The retaining wall bricks are too expensive. I thought that perhaps just a simple cinderblock wall would be ok, but it seems a little too hefty for what I need. It doesn't need to look good, as the backside will be facing away from the viewing angle. This is to create a faux mountain side. What do you think the best action plan would be?
 

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Goodson and others use "Bridge Timbers" you'll find them used a great deal in Natl' Parks for walls, paths, structures, etc...

They look a great deal like a RR Tie w/o the Creosote (more green in color-treated?)...

You could always use a cement block, the hollow one, just make sure you build it on a good foundation.

cale
 

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I have used pressure treated lumber to build a raised railroad, planting bed, pond and creek. You can not just pile the timbers up.... they will start to lean in no time. Pictures are better than words.

Building a raised bed and pond.

Be sure to go on to the next page. 24" high.


And the creek.


Creek

Even tho the creek wall is only about 16" high without much weight behind it.... it is starting to lean out. I will need to get in there this year and brace it somehow from behind.


Craig

edit: I forgot to add. Not all treated lumber is the same. For the pond, I found a great deal on 4X6's from Homeless Depot..... Once home, I found out they were not 4X6. Something metric which did not match well at all with the 4X6's I had already installed.
 

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I used raliroad ties there is a place near me that sells used railroad ties they grade them by quality I bought the cheapest because they had the most character some even had spikes and tie plates on them....I installed them in a zig-zag pattern and drilled a hole through all the ties at every joint big enough to insert a 1/2" galvanized pipe that was about a foot longer then needed the extra was driven into the ground they have been in the ground for about 10 years now, and are holding up very well....


Railroad ties can be seen on the left...



Here you can see the zig-zag pattern I used....Shad sorry I don't have better pictures if you'd like more let me know and I'll tike some for you.....
 

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6"x6"x8' PT timbers. I spike in the first two levels with 2 foot 1/2 inch rebar, 3 per timber. After you get the first course level, it goes pretty fast. You 'll need a heavy duty drill and a foot long 1/2 inch auger. Stagger the timbers and set back each course about half an inch. They cut easily with a small chain saw. A sawzall with a big coarse blade will work in a pinch. The next levels get spiked in with 10 inch spikes four per timber to interlock them. A heavy duty cordless drill and 3/8 inch bit just to start the hole.
Other tools you'll need - shovels, tamper, level, 3 or 4# hammer, 10# sledge





-Brian
 

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Posted By ShadsTrains on 03/08/2009 1:53 AM
I'm looking for a way to build a small retaining wall. I need it to be between 2-3 feet tall and about 30-40 feet long. I'd like to do it as cost effectively as possible. I thought of using pressure treated wood. The retaining wall bricks are too expensive. I thought that perhaps just a simple cinderblock wall would be ok, but it seems a little too hefty for what I need. It doesn't need to look good, as the backside will be facing away from the viewing angle. This is to create a faux mountain side. What do you think the best action plan would be?


I've built retaining walls from cement block, landscape block, railroad ties, and landscape timber. First off, 40' of a 2' to 3' tall retaining wall does NOT fall into the "small retaining wall" world of mine. I assume you are doing this job yourself...versus contracting for it...so WEIGHT matters.

First off, I don't know what you building codes are, but here in California a 3' tall retaining wall is considered structural. In fact anything over 24" technically requires a building permit. If you go over 24" high (here), you must slope the wall back into the hill unless it's a steel reinforced/filled block wall. It can't be vertical at that height without a footing with steel going up the block. You should find out what the building permit requirements are in your area...as they can dramatically drive the cost (for concrete and steel for the footings).

All require some kind of footing for them to work best and, perhaps depending on irigation, a drain system behind the wall (rock around a perf pipe). Freezing water CAN push these walls over in time...NOT good if you have a railroad on top. Landscape block footings are made from base (crushed rock with the rock dust in it....cheap). Landscape timbers and railroad ties should have 2" gravel underneith the base course to keep moisture and dry rot from ruining the wood. Concrete block requires a concrete foundation.

From a cost perspective the cost of the material seems inverse to the effort and skill it takes to install...but completed costs are NOT that far apart in my opinion. Landscape block would cost you around $600 for a 40' wall if you do NOT cap the block...plus delivery. The caps are expensive...and for GRRing, you can just fill the block hollows with dirt. Railroad ties would run you about $450 in material (plus delivery), but you'll probably spend over $100 on saw blades and drill bits to cut/drill the damn things (the creosote and sand in them flat ruins blades). Concrete block sounds cheap (around $150 plus delivery) but it will use up $200 worth of concrete plus another $100 of rebar to make it solid. Pressure treated landscape timbers will run you around $500 plus delivery. All in all, this is a $500 to $600ish job.

So...there's NOT a lot of difference in cost...but there is a HUGE difference in effort to install...mostly due to the weight of stuff. IMHO, landscape block is by far the EASIEST to install. The first couse takes some time to be made level...but from then on, it's just carry and stack. At 40 to 50 lbs per block, it goes pretty fast.

At the opposite end are railroad ties IMHO. I don't know what they weigh, but two guys don't "lift" one unless they're full registered stud muffins. I use a pry bar to scoot them around and just about wore myself out. Getting the fifth course of RR ties UP on TOP of the lower four courses is NOT easy...and you do NOT want one of them to fall on your foot. THAT would be a 911 call. Also, if you are going up 2' to 3', you'll need to drill and stake these...and drilling them is damn near impossible I found.

Concrete block just takes time...it's not hard. It means mixing a good deal of concrete, so you really want a small mixer to mix the footing...that's another $100 to rent one...and you'll be moving a LOT of heavy bags.

PT landscape timbers are light and easy to install...but as Brain pointed out, they must be drilled and staked with a steel landscape rod. That means a special drill rental and a lot of sledge hammer work to drive the rods down. And the building codes come into play here as well...as the walls he showed would NOT be allowed in California...because they're vertical.

If it were me, I'd figure out my exact needs, I'd probably lean toward the landscape block, and I'd go to four places that sell the block and get bids including delivery. In this economy, you might get a really good deal.
 

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Mike,

Don't know if that helped Shad but your information I found very helpful for myself. Thanks so much for taking to the time to post.

Best,
TJ
 

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Discussion Starter #8
Perhaps I should elaborate a bit on what I'm trying to accomplish.. Currently, the area where I am planning phase 1 is relatively flat. I want to build a mountain, or rather half a mountain.. If you'll forgive the rudimentary drawings I'll illustrate... First the cross section. Dark brown is the existing grade. The proposed wall, being 2 foot high would be backfilled on one side to accommodate planting and my ROW running the length. The other side of the wall is where our vegetable garden resides. This wall is really only there to create a berm to hide the veggie garden and give some variety to the landscape.. I envision the wall being taller toward the left side of the plan and eventually becoming shorter down to about a foot on the right side where a path will go in to allow access to the garden.

Perhaps a retaining wall is not the right terminology to use.. How about a one sided planter box? I was thinking that I could use 4x4 pressure treated posts every 8 feet or so anchored with concrete. I was then thinking of using 2 x 12 pressure treated boards screwed to the posts to make the wall. Does this all make sense?
 

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Your basic concept will work with a few mods. You'll need the posts closer together and you need a drain. One drawback is that 2' is about as high as you can go with this approach using 4x4s and 2x12s. Be sure to get at least 2' of the post into the ground. You also want to crown the post hole cement so that water drains away from the post...otherwise even the PT posts will rot off at the base.

8' spans of 2x12 would bow from the pressure of the fill dirt and water in it, so I'd recommend you put posts in every 4'.

Regarding the drain, PT that thin will absorb water from the fill dirt and that will make it bow even with 4' post spacing. I'd recommend that you front the boards with a french drain as shown in the picture below. That will keep the water from setting against the wood and having it warp.



 

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I would add, dig post hole 1 foot deeper than the post portion that is to be set, backfill with gravel fro drainage and set post on gravel. If you have concrete under the bottom of the post, it holds water against the end of the post, the part easiest to rot.
 

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Shad,

I built a raised garden retaining wall just as Mike suggested. I used 4”X4” posts set 30” in the ground (very shallow frost line here) at 4 ft intervals. I used 2”X8” planks because I had to handle them by myself, 2”X12” should work fine. The highest part of the garden wall is 44” at the back corner.




The drain is critical to help reduce hydraulic pressure and keep the soil from becoming a swamp in wet weather. You can see the drain poking out of the wall in the first picture.



I lined the wall with weed barrier fabric before backfilling to prevent soil from leaking through (we have three grades of sand here).

One thing I did that might not have been mentioned, I put in dead men and guys to hold the wall near the top against leaning out from the pressure. I drilled a 5/8”X2’ threaded rod, coupled to an eyebolt with a threaded sleeve, through the wall. The eyebolt had a vinyl-covered cable attached, which was then attached to the dead man. I haven’t had any sagging of the wall so that may have been overkill. “Better safe than sorry.”



It worked for me and another GRRer in my neighborhood. His raised garden has been up for more then three years mine for only two.

Good Luck,
 

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One more thing I should point out...what's in your soil counts. My yard is mostly decomposed granite...with "undecomposed" granite below. One of the reasons I like the landscape blocks or concrete retaining walls is that my experiences installing fence posts has been terrible. Roots and rocks always seem to make the post hole digging very hard...compared to digging a shallow 1' or so deep trench to place base or concrete in to form the foundation...and even if you hit a rock or big root, you can still put the foundation material in around it in most cases.

Of note, when I did the remodel of the house last year following my flood, I had the whole house rewired which included the installation of a new 8' copper ground rod. That's supposed to be simple...you just put a 40 lb jack hammer on the top of the rod and hammer is straight down into the soil. One the third attempt using a second ground rod, the contractor managed to pound the rod all the way down. What was supposed to be a 20 minute task turned into a four hour marathon. The first two atempts hit a rock on the way down...destroying on ground rod on the second attempt.

Fortunately I have a tractor jack, so we were able to pull the rod out after the first failed attempt and reuse it...but on the second attempt, the rod bent when it hit the rock...and we just cut it off. This is the second time I've used that tractor jack...first to pull concrete fence post foundations straight out of the ground...and now the ground rod. Good tool...
 
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