Retaining Wall Details

kkoepp31

Active member
Jun 22, 2020
43
Freeland, MI
Pool Size
14000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-9)
20210616_114635.jpg
Got some questions on building a retaining wall along this long side of our new fiberglass pool. The concrete shown has actually been removed, long story, and it is bare sand as of now while we await replacement concrete. Before the build started we didn't anticipate there being this much of a drop and a need for a wall. I'm now envisioning a 2 to 3 foot wide rock bed between the 8 feet of concrete and where the retaining wall would be. The near end is roughly a 15 inch drop and the far end is roughly 40 inches. Landscapers are saying they can do it no problem, but it isn't cheap and I'm pretty handy. Would a block wall like this be done on a stepped base or should it all be excavated for a level first course? I'm guessing I need a geotextile mesh to make it strong enough, but do I even have enough backset to the concrete to make it work? I worry, whether I or a landscaper do it, that too much material will be pulled away from under the concrete. Any advice would be great!
 

kkoepp31

Active member
Jun 22, 2020
43
Freeland, MI
Pool Size
14000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-9)
Anyone with any ideas here? I think I can do it with geotextile and thinking it's best to not even bother stepping the base course. Just dig it out and run the whole base the full length. The rest of the wall should go fairly quickly.
 

jimmythegreek

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In The Industry
Aug 10, 2017
3,908
Morris Cnty NJ
Just use segmented retaining wall blocks. It's a waste to bury 3 courses and alot of excavated material to deal with. Stepping a wall isnt hard. This is a simple wall ahouldnt be that expensive. What's the overall length and height?
 
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GSD_fanatic

Bronze Supporter
Jul 14, 2021
60
SE CT
Pool Size
23000
Surface
Vinyl
Chlorine
Liquid Chlorine
Looking at the picture, yours is a piece of cake and I'd run the base course level. You have to bury the first course any way, so if you bury a few courses at the short end, so be it. You can also step the base easy enough, just be sure you keep the base level with each step up and evenly compacted. Otherwise with a wall that long, any deviation in height will stand out noticeably. Be sure to add drainage behind the wall at the base before you backfill. Otherwise the wall could buckle from hydrostatic pressure or freeze/thaw. Also if the grade difference is 36" at any spot, you'll need a railing on top of the wall.

I used Versa-Lok for my wall. 200' x 36" tall and kept the base level the full run. No geotextile needed for walls up to 4' tall, at least with Versa Lok walls. I did 3 sides of my pool area due to a grade difference similar to yours and it sits outside the fence. I didn't care for the stepped back look, so I stacked the blocks verticle and are secured to the block underneath with 2 pins. My wall served a dual purpose...retaining wall and knee/garden wall, so I split faced all the blocks...meaning both sides of the block look the same--rough texture. You can sit from either side of the wall in some places as the wall is about 30" above grade. Where the wall holds the grade back, the cap block sits at grade level. Not sure if I explained it clear enough, but can take some pics tomorrow if needed. Depending on your budget, skill set and time frame, I'd even consider doing more than just the length of the pool where the grade drops...but that's just me.
 

kkoepp31

Active member
Jun 22, 2020
43
Freeland, MI
Pool Size
14000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-9)
At the far end where grade is lowest from anticipated pool deck level, it is roughly a 40" drop right now. My idea is to start the wall flush at the end of the pool deck nearest the house giving 2 or 3ft of width for rock and flower bed, where it is about a 15" drop, then running about 45ft and making a turn left and ending up against the pool house. I'm figuring about $2500 in material using clean stone for backfill and for filling the hollow cores of the block. This would be using an 8x18" Clifton block from Menards. I don't need to use Menards material, just add easy to buzz over there to get ideas on my lunch break. Each block is $5.69, so not sure how that compares to Versa-lok.

There is a ton of sand there right now. Should I worry at all about what I backfill with? Will 6" gravel and fines as my base over a separation fabric on top of the sand that is there hold it or do I need to get to dirt?
 

kkoepp31

Active member
Jun 22, 2020
43
Freeland, MI
Pool Size
14000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-9)
And any issues with building up outside the wall at the deep end to get under the 36" threshold? I really don't want a railing.
 

Rich D

Bronze Supporter
Aug 3, 2018
1,029
MA
If you are going to build a wall I think Jimmy's post was spot on. Have you considered just filling the area and sloping it off? Many times this can be a more cost effective approach. It is always hard to judge the grades from pics but it appears you have plenty of room for a filling operation and would end up with a large flat area before you needed to slope it. You can mow a 3-1 slope, plant a 2-1 and slope and fabric and rip rap a 1/1 slope.
 

GSD_fanatic

Bronze Supporter
Jul 14, 2021
60
SE CT
Pool Size
23000
Surface
Vinyl
Chlorine
Liquid Chlorine
I took a quick glance at the website for Clifton block...nice looking blocks! I'm not familiar with the hollow core blocks and have never used them. Kinda surprised they weighed 78#s, which is perfect for what you want. The Versa Lok are 80#s and priced similar at $6 something each. The Clifton blocks can be used up to 40" without geotextile, which is good.

How much sand is where you want the wall base? If only a couple inches, it'll be likely be fine to leave it. If more, you need to dig down to virgin soil and remove the sand. Then bring the elevation back up to the desired height with 3/8 processed gravel. Use 6" lifts and be sure to compact...plate compacter would be ideal. Wetting it down during the process will give you best results for a solid base. Then screed an inch of stone dust to set and level your base course of blocks. A laser is nice to set elevation, but a water level will work just as good for your purpose.

Sounds like you have a good plan in place. I'd say go for it and any questions arise, ask away. I'll offer up any assistance that I can.
 

GSD_fanatic

Bronze Supporter
Jul 14, 2021
60
SE CT
Pool Size
23000
Surface
Vinyl
Chlorine
Liquid Chlorine
And any issues with building up outside the wall at the deep end to get under the 36" threshold? I really don't want a railing.
I don't blame you for not wanting the railing. Building up the lower elevation to avoid any railing will work fine, and I can understand your intentions for doing it that way. But before you go that route, you should reconsider what Jimmy said in post #4. Burying several courses over that length of wall is wasteful. Better to use processed gravel to gain the elevation.

Here's what I would do if it was my project:
Stake out where you want the wall to go. Use a string line with a line level off the concrete deck around the pool to set elevation for the top of the wall. And be sure to decide what height your want the cap block to sit...part of the 40" height or let the cap sit above that height---which is what I would do. You with me so far? Keep in mind, this is just a rough layout, so no need to be exact at this stage. Next dig down where the wall base will be until you hit virgin soil. Get rid of all the sand no matter how deep. Now using that string line you have in place, measure how much rise you need to meet that max 40" of wall height. You want at least 6" of compacted 3/8 processed under the wall. If it takes more to reach the desired height, use the processed gravel.

At this point you will know enough to be able to set the elevation on the downside of the wall to keep the drop at 36" or less...so you can avoid the railing. If you need to raise it up, use semi clean fill. I don't like to use sand on a slope nor do I like to use it for subsoil if I want to grow grass. It drains too much and the grass will struggle to grow. If you want to seed this area, bring the fill up high enough while allowing 6-8" of topsoil for the grass. Once this rough grade is set where you need it, go back and reset everything for wall base...meaning stakes, string lines, etc. I'd recommend you stake out and set the elevation for the entire wall, including where you would go around the pool deck on both ends of the pool. Your blocks are 12" deep, so make the trench for the base 24"wide to allow 6" of processed base on both sides of the wall for a solid foundation. If you have the blocks on hand, you can temporarily stack them at the ends of the wall to help visualize everything...or just use string lines. By doing this, you can make any adjustments if the heights don't work or look good to the eye. Or anything else that doesn't look good.

Just remember, be sure to spend the time to get the base solid and level and get the first course of blocks on the money. You only want to build this once. If a major storm hits a few years down the road, you won't have to worry about the wall failing...because it can happen!

Good luck and ask if you have any questions or don't understand anything. Sorry if I got a bit long winded btw
 

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kkoepp31

Active member
Jun 22, 2020
43
Freeland, MI
Pool Size
14000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-9)
This is great, thank you! Only issue I'm finding with that Clifton block is they do not have corners in stock, which is a bummer because I could otherwise be starting this build as soon as I could get it all delivered. Waiting a month for a few corner block is a huge bummer, but I don't see any other option considering how this is a hollow core block. I'll tall around to see if there is any Versa-Lok available, but I do really like the large format of the Clifton and the price seems very reasonable.

I would probably prefer to just slope the land off but the drop seems too great at the far end of the pool with not enough setback from the property line. The heater would have to be raised and I still don't think it would work well or look quite right. I'm looking in the range of at least $2500 in material and it would probably cost at least double that to have a crew come do it for me, which if they could come next week and knock it out I'd just pay the price, but everyone is so backed up here and I'm always up for a challenge. I should be getting concrete poured by end of next week, so I've got that going for me!
 

bmoreswim

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Jul 16, 2012
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This isn’t an option most people are aware of but you can get a poured (stacked?) concrete wall done without having to have forms made. They can carve the exposed portion if you wish. There may be unbranded additives but Stonemakers is a branded version if you find an installer. Quick install equals lower labor cost. But of course they still have to be available.

You can see an example in my build thread pictures. Link is in my signature. It’s actually the reason I went with the PB I did. He was also a Stonemakers installer.
 

jimmythegreek

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In The Industry
Aug 10, 2017
3,908
Morris Cnty NJ
I install tons of versalok, I'm authorized and certified icpi. It looks easier than it is. Sure you can smack up a wall quick, dont bet that its gonna last. I can't tell you how many walls I've seen DIY that in the end cost as much as hiring a pro. Big thing is equipment. You need a plate compactor, great to have a skidsteer and mini X, and theres tricks. The blocks are 92# a piece, the same block makes corners so it's great. Hollow block is usually 8" so it's harder to smooth grading steps, amd you need corner. Plus you have to fill each block with clean stone. Royal pain to work with in my opinion. Most of the hollow block has a small lip that holds it back amd they like to snap off over time, only a wall that pins is a quality wall.
 
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