Retaining Wall Post Question

[dieselscout80]

We need to build a retaining wall 30" tall about 200 feet long along our pond. The wall would be to make it safe to mow and walk along the edge.

We are planning to use ground contact rated 2"x8"x16' for the wall four high for most of it, but some may ony be three high.

If we drove 6.5 foot steel t-post on 48 inch centers into the ground until only 29.75" was above the ground and place a deadman every 8' would that work?

This route will be much less work than 4"x4" posts.

 

[GPintheMitten]

I doubt the t posts will add much strength.

I assume you are placing the posts outboard of the 2 x 8 s. If not you should. The dead man's should have a T on the ends to anchor against the force pushing out.

I know 200 foot wall will be expensive but I have my droughts about the strength of using 2 by s. Might work with closer set posts.

I built a retaining wall much shorter but higher. Used 6 x 6 s with one below grade and many deadmans.

It sounds like a big enough and expensive enough project to get a consulting engineer involved.

 

[bcp]

If I needed to build one with 2x8's and T-posts, I would build it one board high, like wide stair steps, maybe 2 feet apart. (or wide enough for a mower)

Bruce

 

[dieselscout80]

Here is a short one we built out of 6x6s, but I'm hoping to keep the expenses low on this one.

 

[dieselscout80]

If we used railroad ties how often would you run deadman back into the back doea a 35" tall wall?

I'm thinking of just putting the deadman in the row just below the top roll, but would they need to be every 8' or could I go to every 16' in that roll?

 

[GPintheMitten]

I didn't put my deadmans all on the same level. I put some low, some in the middle and some toward the top.

 

[MacLawn]

diesel, I think ye did that short one good. But ground contact treated 2x8s might be hard to find, I'd want to use maybe 4x6 posts. Stagger'em like old GPinthe said too, plenty of T posts for strength. Ye just cannot cut corners in building stuff. Ye place looks good!

 

[dieselscout80]

I didn't put my deadmans all on the same level. I put some low, some in the middle and some toward the top.

How tall is your retaining wall?

 

[dieselscout80]

diesel, I think ye did that short one good. But ground contact treated 2x8s might be hard to find, I'd want to use maybe 4x6 posts. Stagger'em like old GPinthe said too, plenty of T posts for strength. Ye just cannot cut corners in building stuff. Ye place looks good!

Thanks

A local yard has ground contact rated 2x8s.

 

[GPintheMitten]

How tall is your retaining wall?

I had 2, one was about 4' the other about 6 '.

 

[dieselscout80]

I had 2, one was about 4' the other about 6 '.

This one will only be about 30 inches tall.

 

[Streetcar]

Four ft spacing on supports is excessive for the 2" dimensional lumber.
What are you planning to use for deadman?

 

[dieselscout80]

Four ft spacing on supports is excessive for the 2" dimensional lumber.
What are you planning to use for deadman?

Do you think 36" is ok?

I've thought of using 3' chunks of 4x4s or 4x6, but I also thought of using concrete blocks. With the blocks I would try to use chain (1/4" or 5/16") between the block and the wall.

If I go with railroad ties I'd use the ties in T shape, but the chain to a 3' chunk of rail road tie would cut down on the digging.

 

[GPintheMitten]

How are you going to get the chain taught? If there is any play at all the wall can give out until it gets taught. Could easily get 2 inches of slack.

 

[dstig1]

I've never seen ground contact rated 2x's around here. I did retaining blocks - the 70 lb size - for my ~100' wall at 2-3' high or so. The time is all in the base prep. Get it level and compacted, and it will be good. Been solid as a rock for 16 yrs now. Not a bit of movement. The block stacking goes fast, and not too expensive.

 

[dieselscout80]

Here is a picture of where the wall will be built.

At 30" high the wall will give us plus 60" of flat space that will make it safer to mow.

The edge of the grass/plants is the normal/high water level.

Marked location.

 

[RedNeckRacin]

I don't think the t-posts are even worth considering. The best bet in that moist of environment would be masonry. The wall is low enough that you should be able to just stack the blocks with a slight rearward tilt after you prep the base. Drainage would be a major concern of mine as well.

 

[LD1]

Go retaining wall block, do it right, and it will last forever. Not sure what your lumber prices are, but what you describe would cost around 1800-2k just in material here.

8x18 blocks are $4 each. A 200' row and 4 block high would require 534, ~$2200 worth of em. I'd pay to have em delivered too though. And it will look alot nicer than wood IMO.

 

[dieselscout80]

Go retaining wall block, do it right, and it will last forever. Not sure what your lumber prices are, but what you describe would cost around 1800-2k just in material here.

8x18 blocks are $4 each. A 200' row and 4 block high would require 534, ~$2200 worth of em. I'd pay to have em delivered too though. And it will look alot nicer than wood IMO.

Are you refering to concrete block for building or retaining wall blocks and do you have a link to them?

 

[The Suburban Farmer]

One of the worst things I've had happen is for the deadmen to rot or become loose from decay. That requires an ENTIRE redig and rebuild of the wall. You might want to consider making the deadmen out of pipe instead. If the wall rots, you can replace the pieces without having to dig up and replace the deadmen. If you think you may be consistently wet and that you might have to replace the wall at some point, you might want to consider making the deadmen "permanent" and "re-attachable" to ease future repairs.

I've used a setup like this in wet areas in the past and it worked VERY well. Ultimately, we had to replaced the retaining wall 4x4s due to decay (after about 15 years) but we could just reattach them to the existing deadmen with no new digging.