# Steel I-Beam vs Wood Post



## utex01 (Oct 19, 2011)

Hey everyone,

I'm building a short length of retaining wall and at its highest point its about 3 ft. Its a very shallow area and I don't have much depth to work with so I wanted to use steel i beam posts to make the wall as narrow as possible. I was thinking of using 3 inch i beam to hold back the 3 ft of earth behind it with wood 2x8 in between. I've seen 4x4 posts used and 4x6 posts used in the same application but not such a small i beam. I plan to set it 3ft in the earth.

Does anyone see any problem with any of the above? I realize this is a landscaping question but I'm really asking about the strength of the steel i beam in this calculation.

Thanks


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## Ron6519 (Mar 28, 2007)

Are you putting drainage behind the wall? Generally you would dig out behind the wall about 12-18" and install landscape fabric against the soil. Then put a drainage pipe at the base of the wall to carry the water away to a lower area. The pipe would have a sock over it to keep dirt out.
The dug out area would be filled with gravel about 12" from the top. The landscape cloth would be folded over the top and the remaining space filled with soil.
I'd concrete in the steel.


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## ddawg16 (Aug 15, 2011)

Steel will rust....wood will rot.....and as Ron said, you need to provide drainage.

Personally....I would do rock/concrete....or at a min, concrete in the steel as Ron suggested.


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## utex01 (Oct 19, 2011)

Sorry guys - I left that part out. I will be setting the posts in 8 in diameter holes 3 ft deep full of concrete. I will be able to put 6-10 in of drainage behind. This is right on the property line so I don't have much room to work with.


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## stadry (Jun 20, 2009)

you're fine :laughing:


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## Daniel Holzman (Mar 10, 2009)

You are building a miniature version of a wall type called soldier pile and lagging. The soldier piles are the vertical steel I beams, the lagging is horizontal wood "slats" that are inserted into the top of the I beams and essentially hammered downward into position. This technique is commonly used on very large projects, I have never seen it used for small walls like yours, but it should work fine. In commercial projects, the steel I beams are used like piles, hammered into the ground, I have never seen them set in concrete, too expensive and time consuming. You can probably do the same, just hammer the steel into the ground with a 12 lb sledge until they are embedded about the same or greater than the exposure (i.e. if they are going to stick up 3 feet above grade, hammer them in at least 3 feet below grade).

Install all the I beams, then cut the wood to length and install the wood lagging. Should be a good system. Only thing to be careful about is the spacing of the I beams, you are going to need to use thin wood boards if you want to insert them in the flange of the I beam, so you will need close spacing of the steel. Alternatively, you could simply put the lagging on the uphill side of the I beams and install a few sheet metal screws to hold the lagging in place until you can place the backfill. Then you can use 2x pressure treated boards. Once the backfill is installed, those boards are not going anywhere until they rot in 20 years or so. The steel will be there for at least a hundred years.


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## stadry (Jun 20, 2009)

or a highway noise barrier :thumbsup:


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## utex01 (Oct 19, 2011)

Thanks Daniel,

You mentioned to be careful regarding the spacing of the steel - do you think every 23 in or so is sufficient? I was going to space them double that distance, but I have an extra steel beam so I figured I might as well use it.

Thanks


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## Alynnc7 (Apr 24, 2021)

I have been looking everywhere for I beams. Where did you get yours? How’s your wall holding up?


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