Retaining wall advice requested

Holbs

Holbs

IPCT+ Member
May 1, 2019
2,254
3,563
Reno, NV
Has anyone installed retaining wall? :) Good way to open a topic.
My 14 year old 6 foot rear fence of 25' blew down during latest wind storm. It's a combo fence: 3' of timber retaining wall using 2"x12" boards and additional 6' of fence post....making each post a 12' 4"x6" post spaced 6' apart from each other for a total of 65' length. Home insurance sent me claim $$$ to repair/replace what broke which is just 25' of the 65' retaining wall/fence line and to hire contractor. I am going the DIY route instead. So far, I have removed all 65' of timber retaining wall and 65' of cedar fence picket boards. In progress of removing the 4x6 fence posts with my Hi-Lift jack & chain. I am replacing all the timber retaining wall with retaining wall cement blocks. Not the fancy VersaLock blocks but cheap ones from Lowe's as this retaining wall will never be seen by human eyes and is only 3' tall (anything over 4' requires county/city engineer).
From all the pro's and experience landscapers, using Geogrid sounds mandatory every 2' of earth. And pinning each block to the next one.
Has anyone built a retaining wall in the 3' height range going the DIY route that has survived years? I could of went back to using timber but I would have to do the same project in 10-15 year time span.
 
Drainage, drainage, drainage. I would recommend at least 18 inches of clean 3/4 angular stone(#57stone by me) backfilled behind the wall with a drain tile at the bottom. Daylight it every about 20 or 30 feet. Depending which block you use will determine how big of a compacted base you will need. The cheap blocks with the lip on the back will eventually fail, again. They could get push up and out in freeze thaw cycles.

Geogrid for a wall that high is a must for safety and non failure if done properly

Ground movement and settling can also unlodge the blocks with lips on the back
 
Last edited:
grumpywilson said:
Drainage, drainage, drainage. I would recommend at least 18 inches of clean 3/4 angular stone(#57stone by me) backfilled behind the wall with a drain tile at the bottom. Daylight it every about 20 or 30 feet. Depending which block you use will determine how big of a compacted base you will need. The cheap blocks with the lip on the back will eventually fail, again. They could get push up and out in freeze thaw cycles.

Geogrid for a wall that high is a must for safety and non failure if done properly

Ground movement and settling can also unlodge the blocks with lips on the back
Click to expand...
Grumpy..I am financially limited by the measly insurance claim. I was suppose to do 1 for 1 swap out of timber, with timber. I went for the blocks and DIY route to keep in the black from the claim $$$ as I know the timber path would of resulted in doing the same thing 10-15 years down the road. Example: the much touted and respected Versalock blocks would of cost well over $3000 for 65'. If I planned for this project and saved up $$$, I might of went for it. I opted for the cheesy blocks with lips because is only 3' tall of a retaining wall (I will be doing 10"-12" 3/4" gravel behind for draining along with a French drain), and because the wall itself will never be seen after I put up a fence.
 
On the cheapo. Gotcha. Oh, and no geogrid for 3' tall wall. I was thinking 6' high not realizing at the moment that you said 6' fence. Well, is it possible to find a cheap hollow block that you could fill with clean 3/4 stone from the top as you stack them? That would help lock them in place better. I think that would be your best bet if you really want it to last. I think I have seen those at Lowe's or Home Depot.
 
Yea... Home Depot sells the flat top ones that are hollow underneath. Ordered 260 to be here by next week Tuesday. Sadly, Lowes has the 2 holes all the way through blocks I would prefer over HD as I could fill with gravel, but they are out of stock for a time.
Was thinking of making my own holes with cold chisel on the HD ones :)
 
This is what I started out with:

IMG_20200323_180421.jpg

This is where I am at. Excavated 65' long x 3' tall x 14" deep by hand. Working on 4x6 posts and footings this week/weekend.
Since never done anything like this before, I just wanted to ask of any opinions or suggestions. I've read alot and tried to do as much DIY research as I could...but there is always the "why didn't you....." in the end :)

IMG_20200530_145739.jpg
 
Excavation looks good so far. However you put your block down, just make sure it's compacted as well as you can get it. How are you integrating the fence with the wall?
 
Yes, will be doing 24" gravel footing under the first layer of blocks for the frost line (egads... some places required 36"!).
I have a hand compactor just for this project.
The fence is a "learn as I go" project. Pretty sure will be using the Postmaster metal fence posts in 24" cement footings. I just do not know how close/far I can be to the drainage gravel line.
Since wood working is my #1 amateur hobby, this is what I'm trying to go for:
270739-438x.jpg
 
  • Like
Reactions: grumpywilson
Does your area have code on footing depth for dry stack retaining walls? 24" seems excessive to me. I would suggest to put the first course of block below grade to prevent a bottom wall blowout. If you can't do that, maybe knock holes in the top of the block and pound rebar down through the block into the soil to keep it in place
 
hmm.... you bring up good point. all the footings for retaining wall I read were from poured concrete footings, not gravel. I have a little more research to do on that.
What is not visible in the pix, there is a cemented pathway under all that timber/dirt for the city draining to sewer. The existing 4x6's are butted up against that concrete. That will help for the base blocks. I'm getting 6"x16" blocks. Was going to put the first block set 3" under ground level, 3" above ground level.
 
better pic of that city concrete drain channel and my massive 4x6 footings I have to work with
IMG_20200530_183749.jpg
 
How long are your fence posts going to be? The depth of the wall plus two feet in concrete plus six feet above the wall? I'm just trying to see the big picture of the construction. Does that pathway run the length of the wall? I'm also guessing that your jack is on the concrete pathway? If so, you could put the face of the block against it to prevent it from kicking out. Not sure if the town would like that if they had to replace the pathway though.
 
Haven't seen a city employee back in this area in 20 years. I think they forgot it's there actually. And yes, that pathway (runoff is more likely the vocabulary I'm looking for) runs the entire length of that fence line, including my neighbors, and then 60' behind to a sewer drain.
Fence posts will be 7'6" (for some reason, Postmasters do not come in 8'). 2' in ground, 5'6" above ground to attach to fence.
 
Maybe as your building the wall you can place a 8" sonotube or whatever size you think you could get away with right behind the wall for the fence post. Just remember that as you go up with the wall, it's also going to move back because of the lip. So you might have to put it a few inches behind the base layer of block. And when the wall is done concrete the posts into the sonotube.
 
There is this awesome guy on YouTube that just spews info on all sorts of things. His name is Stanley "Dirt Monkey" Genadek. Go to his playlists and look for retaining walls. He has 15 or 20 videos up about them. I wish I knew about him before I spent tens of thousands of dollars to build my walls and patio myself years ago.
 
You must log in or register to reply here.
Top Bottom