Retaining wall height and footing

[cbrown]

The property next to ours is being developed. The natural slope of the lots from front to back is about 8' (i.e., we have a walk-out basement). It turns out that the developer has decided to flatten the adjacent lot by filling it in and is building a retaining wall which is level to the ground in our lot at the front but will be at least 6' above our level at the back (also along his back property line with the back neighbor). There will be a 4' fence on top of the wall. I guess I'm a little surprised that you can legally just plop something that size down on the property line—I'm pretty sure I couldn't put up a 10' high fence, but the wall will be on the north side of our property, so won't shade our yard, and I suppose it would keep fly balls from going out.

I am concerned about the construction of the wall. It's being built out of prefabricated concrete sections, about 3' high and 2' deep, and 8' long. They have a ridge on top and groove on the bottom to align them when they are stacked, two high in this case as I understand. But they are being placed on a gravel bed which is certainly not more than 6" below the level of our property at the back. I would have thought that they needed a solid footing below the frost line (this is Massachusetts) tied together with rebar. I don't see what will keep them from being pushed over onto our property, sooner rather than later, with a full yard of dirt 6'+ deep behind it. Do I need to move our sandbox away from the impending avalanche (or talk to the local inspectors), or am I overly concerned? Any thoughts?

Thanks,

Christopher

[crokett]

I know the retaining walls built of the smaller dry stack blocks are set on a gravel bed. I don't know how deep the gravel is though. As far as the wall falling over, he may be tying it into the earth behind it with ties before he backfills.

If you are concerned, you can probably get the building inspector out there.

[Tom Slick]

you can certainly call the local building dept, the builder should have a permit already. around here anything not flat requires a permit.
When laying dry stacked interlocking retaining walls you only bury 1 course (6-10" tall) and you can build the wall 3' tall or so.

[pelligrini]

There are some systems that tie back into the earth it is retaining. The ties can be put in during backfilling, like crockett said, some can be pushed in. Around here I think any wall above 4' has to be engineered. The soils may be enough without needing a footing below.

Feel free to ask the inspector or bldg. dept. to address your concerns. You do pay part of their salaries, one way or another.

[Tom Slick]

If you want to keep it on the lowdown you could just call and ask for information. you don't have to accuse anyone at this point.

[just started]

If your area is anything like mine, the building permit and plans should be available at the township or county website.

[Hellrazor]

They are playing with fire if they are building a retaining wall 6'high that is free standing and doesn't have a footer in a cold weather zone. Hydronic pressure can cause them some serious problems too. I would call the local municipality office and make it an issue of it. I don't see that as a safe building practice by any means.

Ask them about:

1. Lack of a footer below frost depth.
2. Setbacks from the property lines. A retaining wall might not meet the definition of a fence which can be placed on the line.
3. Height of the wall & fence.
4. Liability if the wall fails due to their poor planning.
5. Does the style of wall have an engineering company signing off on its ability to withstand hydronic pressure and any frost related issues.