[ajmikola]

Hello and thank you to anyone who can help me.
Over the years I have come to love doing DIY and have tackled quite a few things through trial and error and I have now arrived at putting up my first retaining wall.
As you can see in the pictures, the slope under my kids tree house (which me and my buddy built) is eroding rapidly exposing roots of a 50+ foot tall pine and washing dirt down into my driveway. The red arrows represent erosion, the blue represent the direction of water flow. I have to contain the erosion fast because it appears the rate of erosion is increasing. (The red box represents a catch basin system that i installed and spans the entire yard to assist with drainage, which subsequently fails quite often due to mud :vs_mad: from.....you guessed it, erosion).
My goal is to put up a interlocking retaining wall from HD or Lowes, dimensions being roughly 22 feet wide x 3 feet high and then back filling the area with top soil to support the tree roots. This also includes putting a drainage pipe behind the second course and back filling / tamping as I go up. I have envisioned something like retaining wall pic #4, this is from the Iscape app.

My biggest and first question is: How should I design my footing? Meaning, how deep should I DIG and how high should the aggregate be inside the trench so I can lay the first course and how much block should be above ground level?

Also, does this plan seem feasible for a DIY guy or should I let a professional do it?

Any constructive thoughts, tips, or recommendations welcome. Cheers.

 

[de-nagorg]

Those roots are going to be a pain to go around, avoid cutting any that close to the tree, they are holding it up.

Your footer should be about 1/3 the above ground height, and wide enough to be stable.

Ideally one block is buried, before the above ground blocks are placed, so your gravel should be at the height to bury the first course of block.

You can space the buried block apart where the roots are, and use gravel to fill the space, to allow water to get to the catch basin, you are leaving the basin?


ED

 

[ajmikola]

Thank you for the reply. So 1/3 the height of 3 ft is 12 inches. So a 12x12 inch trench?
That means 8 inches of aggregate and the first course of stone given the height of the block is 4 inches tall.
Thanks again!

 

[HotRodx10]

This is a fairly straightforward DIY job...if you have the muscle for it. The blocks are a bit on the heavy side for some folks, but if you can handle them, you can do it.



For a 3' high wall (your pic #4 makes it look like it's only 2', if the 8" high blocks are to scale), all you need for a footer is something you can level easily on undisturbed or recompacted soil a few inches below the ground. Digging down 6", scraping off the loose material, and putting in a couple inches of sand, should be an adequate base.

 

[de-nagorg]

Just sand as a base, will not work.

He needs gravel to surround and channel the runoff to the basin, covered with filter fabric to hold the silt from clogging the basin, and then the first buried block, then the remaining blocks and fill dirt over the drain pipe behind the wall.


ED

 

[huesmann]

Good photoshop work, by the way!

 

[3onthetree]

Retaining wall seems overkill, here are my thoughts. I do not see any roots above grade, and slope matches the slope of the adjacent yard there prior to the fort. Any linear digging will encounter some hefty roots. Dragging feet on the swings and traffic under the fort has eroded the ground cover (but not deep enough to expose roots, yet), allowing dirt runoff.

I would just put edging (your material choice) around the fort and fill with mulch. Under the baby swing between the two posts make the edge a bit higher (but no need for a retaining wall that raises grade level with the base of the tree) to keep the slope relatively shallow to prevent mulch washout.

Restore grass/sod around the catch basin and between house. Then move the two big kid swings out from under the fort on an 'A' frame extension. This would also be safer without the post, prevent interfering with the rings and them hitting the house when they jump off.

 

[HotRodx10]

Just sand as a base, will not work.

As a leveling pad for the bottom course of blocks to sit on, it will work just fine, which is all I was suggesting the sand for.

He needs gravel to surround and channel the runoff to the basin, covered with filter fabric to hold the silt from clogging the basin, and then the first buried block, then the remaining blocks and fill dirt over the drain pipe behind the wall.

Seems like a reasonable way to handle drainage behind the wall. Depending on where the wall is in relation to the basin, the drain may have to dive under the wall to reach it, but if the runoff is to be captured, it should be captured behind the wall, not under it, so that the soil under the base does not get saturated and soft. If it's backfilled with soil, a drain shouldn't be necessary, or useful, since the runoff will just go over the wall, anyway.