Retaining wall rebuild

[Mark Rainey]

On house I bought 12 years ago, walk out basement retaining wall is falling apart. I am thinking of rebuilding - it is only 10 feet long. It looks like the previous owner stacked concrete blocks in front of the original wall to slow the collapse of the wall. I will pull all the blocks and will dig down about 6 inches below grade, put some gravel down, build my wall and put some gravel in between wall and dirt. If I do not rebuild do you think the dirt will gradually collapse to my basement door?

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[Jack Frederick]

With rain & snow it will eventually migrate to the door and ice will be a hazard. The biggest issue I think is containing the moisture. Does it migrate into the basement now at the footing/wall joint? How do you manage the sub grade moisture now? I think you will end up dong this retaining wall. If it is bugging you now…just wait.

[Lee Schierer]

I agree with Jack. Over time the soil will move down the slope from freeze/thaw cycles, heavy rains and snow melt. Water will accumulate on those pavers in front of your door and find its way into your basement unless there is a drain or a roof over the whole area.

[Bill Dufour]

I have read that things built where the ground freezes have to have a foundation at least as deep as the frost line or it will just get heaved around every freeze thaw cycle. I think you need to go below 6".
Bill D

[John K Jordan]

I have seen a number of retaining walls that looked great when installed then started to bulge/collapse over the years. Water is the biggest enemy and will build up in the soil behind the wall. Unless the wall is very short the water must be drained - you want to retain the soil, not the water.

How you build it depends on several things including the slope, shape, and drainage of the ground behind it, the height, and the materials used. I didn’t see how high your wall is. You can sometimes build in drainage holes but that requires having somewhere for the water to go after it comes through the wall. And a means to keep the water away from the house.

If practical, the best thing is a drain, built sort of like a french drain under the soil behind and next to the wall. Built with a drain pipe it would carry water away from the wall and release it somewhere away from the wall and house. This would probably require removing the entire wall and rebuilding it from scratch, installing the drain and shaping the slope behind the wall. (All this is best done during a dry spell.)

There is a lot of info on the internet and a bunch of YouTube videos. I didn’t watch any and like most subjects, some (most?) may not have good advice.

You might get an architect, structural engineer, or contractor to look at your situation and give you an idea of what it would take and a quote if you want them to do it. Tall walls in some cases may require major excavation, special construction, and anchors and support structure. Some situations call for a concrete wall behind the pretty wall. I would ask any contractor for several references of local retaining walls he’s built that are at least 10 years old then go look at them and talk to the owners.

Depending on the jurisdiction, you may also need a building permit.

A quick search found this page which mostly seems reasonable.
https://www.familyhandyman.com/article/how-to-build-stronger-retaining-walls/

My son is an architect. Years ago when we traveled to visit schools one dean in a respected university told us that much of architecture and the lawsuits concern keeping water out of the building. The basic rules I follow when building things myself are if possible slope the ground away from the building, and/or design drainage appropriate for the site and climate. Fortunately here in the lowlands of TN we don’t have to deal with the snow, ice, and depth of ground freezing than many have. (18” here) Our farm is at the top of a ridge which helps too!

JKJ (expatriate, western PA)

[Mark Rainey]

Thanks for all the helpful advice. Jack, I have not have any water migrate into the basement yet, the patio gently slopes away from the basement. Bill, the frost line in my area is 40 inches. If I was going with a concrete wall or mortared block, I would have to go below frost line. My understanding is that segmental block will move around and shift with the seasons, but that is OK, as long as it is installed properly. John, good tips, if I hire a contractor or do it myself. I am having a heck of a time getting contractors to come out and give me estimates. Masons seem to be all booked up this season.

[Jack Frederick]

Should you choose to go with block I’d build pilasters back into the slope to increase the strength against the freeze thaw cycle. Given that you are right against the building and it appears somewhat protected I’d tempt fate and go to a 24” footer.

[Ron Citerone]

I just rebuilt part of a retaining wall and know it is not best practice, but short of a total rebuild I did it anyway. I did however see some utube videos by wall contractors that go into detail about proper practice. You might want to spend an evening searching there.

[Ole Anderson]

You will be fine IF you build using a pre-designed segmented block retaining wall. Check with your local landscape supply. No deep foundations, pilasters or block tiebacks needed, but a proper gravel foundation and drainage behind the wall are important. Taller walls are usually built with a geotextile between backfill layers to act as a tieback. All detailed by the block manufacturer.

[Mark Rainey]

You will be fine IF you build using a pre-designed segmented block retaining wall. Check with your local landscape supply. No deep foundations, pilasters or block tiebacks needed, but a proper gravel foundation and drainage behind the wall are important. Taller walls are usually built with a geotextile between backfill layers to act as a tieback. All detailed by the block manufacturer.

Thanks Ole, I appreciate your advice.. the wall will only be about 18 to 24 inches high, so I think Versa-Lok blocks on some compacted soil with drain tile should work.