ᐅ Frost-Protected Foundation for a Wall Adjacent to an Existing Neighboring Boundary Fence

Good morning everyone,

I hope the title is clear. Here is the issue: our neighbor has built an L-shaped retaining wall as a boundary, slightly set back from the property line (about 2cm (0.8 inches)).

He does not allow us to backfill against his L-shaped wall. Therefore, we are planning to build a wall along the property line as well. This wall will be approximately 70cm (28 inches) high on average, and up to 100cm (39 inches) at the highest point.

How deep should the frost-protected foundation be at this location? Should it also be 80cm (31 inches) deep, or can it be shallower because of the neighbor’s existing wall?

If water can flow beneath the lowest point, I think the wall can shift. And that can happen even if something frost-resistant is built right next to it.
(my consideration as a non-expert)

Xhnnas schrieb:

How deep does the frost-protected foundation need to be at that point? Is 80cm (31.5 inches) depth still necessary, or can it be shallower because of the neighboring wall?

The frost protection depth depends on your soil and climate conditions.
I don’t see how a wall 2m (6.6 feet) away would affect the frost protection depth.

It says something about 2 "zentimeters"

Uh, yeah. Got up early this morning :/

Basically, the neighbor’s foundation should be beyond the property boundary. This would still require a frost-resistant foundation on your side. Water could possibly seep over to the neighbor’s property, but that’s not certain.

If the L-shaped blocks are only 2cm (1 inch) away from your property boundary, I doubt that the foundation was entirely built on his own land (although I can't completely rule it out; it's possible). However, if the foundation does extend onto your property, it shows a clear lack of common sense on his part to forbid you from backfilling. (You might be able to request removal if it’s proportionate.)