Border fortification, neighbor and border construction

Hello everyone,
Following situation: We are building in a gap within an established residential area. In principle, we have exactly one neighbor who affects us. Because he has his garage built directly on the property line and has had it there for 10 years. Now we also want to build a carport on the very same property line. Due to the slight slope, our property lies a good deal lower. Unfortunately, the neighbor only has a concrete slab with a thickness of 15 cm, and to prevent it from being exposed, he at that time pushed an obviously artificially created earth mound from our property up to the base of the slab. This mound does not correspond to the natural course of the property!!! Furthermore, adjacent to his garage, he has laid L-shaped stones to stabilize his property. These lie in lean concrete, which along the entire length of the installation also extends 40-50cm into our property.

What can I do here, legally but also technically? To realize our project on our property, we would have to remove the created earth mound and take away part of the lean concrete (otherwise we cannot place the masonry carport including tool shed on the boundary). Do we have to underpin the neighbor’s slab, even though the mound is clearly artificially created? How does the stability of the angle stones look? What would such underpinning cost? Do I really have to forfeit the design freedom of my property?

Thank you very much for the help and contributions

Basically, a builder has no business on the neighboring property without the owner's consent, especially not to erect any structures. However, I assume that you were not the owner ten years ago. Therefore, you would need to verifiably research the circumstances from back then, who asked whom and who allowed whom what. First, I would talk to the neighbor, present your project, point out the issue, and propose a solution. If the neighbor is uncompromising, uncooperative, aggressive, or otherwise reacts unfavorably from your perspective, I would take a look at their building file at the building authority (of course, you can do this before the conversation). Did they build as approved? Are the original and planned heights recognizable? Is there a development plan? Are existing heights visible there? Are there regulations regarding the heights (single-family house, eaves, ridge, plinth, knee wall)? If there are discrepancies, you can look for a solution together or immediately involve the approval authority (for good neighborliness!).

Basically, it is not allowed to cantilever the support due to height differences onto the neighbor's property. His garage/carport or similar would have had to be narrower so that the support for height compensation is located on his property. 40-50cm onto your property over the entire length is several square meters.

As already mentioned, you should first see if you can somehow reasonably still get your carport/garage there, e.g. by setting it a bit higher or something else? If there are additional costs, talk to the neighbors and try to find a reasonable common solution. A garage is, I believe, subject to approval in every federal state, so there will be a permit or something similar with the planned position along with all the other details. I also can’t imagine that you are simply allowed to support your garage 50cm on the neighbor’s property, no matter whether approved or not. He simply would have had to make his garage 50cm narrower.

What exactly does "a good piece deeper" mean and how far are you currently with the construction? Normally, through excavation for soil replacement, the base comes "a good piece" higher anyway (depending on what the development plan allows). Maybe you can build over this slope? Otherwise, as always: a picture says more than 1000 words.

If all else fails, it will very likely lead to having to dismantle it. Then you’ll be in trouble with the neighbor (it will cost him a fortune) and you certainly won’t have any pleasure with him.

I also can’t imagine right now that you can just support your garage 50cm on the neighbor’s property, regardless of whether it’s approved or not. He should simply have built his garage 50cm narrower.

Sorry for being direct here – but why shouldn’t you be allowed to support your garage on the neighbor’s property if it’s approved like that? Of course you can – if you know how it works or it is actually approved (!). In these cases, dismantling by 50cm may possibly not help because the embankment can/must be considered as its own structure and then it in turn triggers an easement.

if nothing helps, it will very likely lead to dismantling. then you’re screwed with the neighbor (costs him a fortune) and you definitely won’t have any fun with him.

Dismantling here is the least likely of all options even without inspecting the files, so I wonder why this is repeatedly used as a threatening tactic by laypeople and even by employees of the building regulations offices. Such trivialities (!) can be resolved formally and structurally by multiple, more elegant, and significantly more cost-effective means. If this would lead to dismantling even in a small percentage of cases, the courts alone would be busy with this until the next Ice Age.

Regarding the matter/solution (all variants must absolutely be clarified on site with an architect/surveyor; without file inspection and local measurement this cannot be finally assessed!)

1st variant

The neighbor registers an easement on the property for the garage and the structure “embankment.” Matter settled, further planning depends on the status then available. The trick: the easement can possibly allow the tenant’s garage to be built, so that after all work is completed the easements can be deleted again – both garages then stand at the same height on the boundary, the easements become obsolete and everything is perfectly fine without dismantling.

2nd variant

The embankment made 10 years ago (possibly illegal) is meanwhile considered as matured/original ground surface. Artificial embankments legally become the “natural” ground surface over time – when this happens is subjective, there are many court rulings with very different timeframes. After 10 years this is quite realistic though, there are rulings arguing with significantly shorter intervals. If the building authority follows this view, the neighbor’s garage is at the boundary (!) about 3m above ground level and is therefore standing completely correctly – and the new garage to be built also has as its planned height at the boundary (!) the ground level measured there, in this case the top edge of the embankment.

The rest is a structural task for the architect; in short: I am sure that in cooperation with the building authority, architect, surveyor, and last but not least the neighbor, a solution can be quickly found here that is far from dismantling.

Best regards Dirk Grafe