Neighborhood concerns regarding exemption from the floor area ratio

I can't give you an expert answer as I'm not familiar with the subject, but I would like to encourage you and your neighbors to take action against it with all means available to you. If you don't, you will probably be annoyed about it for a long time; better some stress now than trouble for a long time.

Yes, but be careful. The actual shadow cast depends on the position of the house relative to your own garden. This variant might even be better in terms of shade than a smaller house a few meters away but offset. Or the 2m high garden fence on the slope might completely block and shade everything.

Therefore, be well informed about the situation and no matter what happens, don't be upset for too long. The alternative you don't consider could end up being worse.

You guys make it so exciting. May I ask as a newcomer, who is Escroda? Do you have to know him?

Our survey technician No one here who speculates, but rather is concretely credible

The most important question would be, (1.) whether the neighbors must be involved in the permission for deviation according to §66 ThüBO para. 1 in accordance with the “public-law protected neighborly interests” mentioned therein – which, for example, must also be taken into account according to § 31 Baugesetzbuch para. 2 – i.e. whether the signature is required.

In the crosspost, a construction expert has already given you the helpful hint regarding the judgment of the BVerwG 4 C 7.17 from August 9, 2018. While the judgment itself may still give you hope for defensive rights, the key points already indicate what the reasoning of the judgment clarifies: In order for the degree of structural use to have a neighbor-protective effect, very special conditions must be present. I do not see these in your case. And therefore, the obligation to involve the neighbors according to §69 Thüringer-Bauordnung is also not applicable.
You would have to prove the neighbor-protective character of the floor area ratio specification, which you will not succeed in, since on the one hand a different development plan applies to you and on the other hand, the impairments you mentioned are only indirectly related to the planning law floor area ratio. You directly complain about increased shadow casting, which, however, is regulated by the building code distance regulations. Only if errors were made in the calculation here or a related deviation was approved are your rights violated.

And (2.) does §17 Baunutzungsverordnung – with its upper limit of 0.4 in general residential buildings – apply in the development plan area?

The upper limit applies to determining the degree of structural use, i.e., for the plan drafters. However, they complied with the upper limit since they set it at 0.3. To check whether a concrete construction project is approvable, §19 Baunutzungsverordnung is applied, which allows several possibilities for exceedance:
... further exceedances of minor extent may be permitted ...
... As long as the development plan does not stipulate otherwise, in individual cases compliance with the limits resulting from sentence 2 can be waived ...
And this brings us to the many open questions of your two threads:
How do you know what your neighbor intends to build if you were not involved?
How do you know that he has received an exemption?
Where does the information come from that a decision was made not according to §31 Baugesetzbuch but according to §66 Thüringer-Bauordnung?
The described factual situation appears extremely confusing and imprecise. A deviation from the stipulations of the development plan, such as exceeding the floor area ratio, requires an exemption according to §31 Baugesetzbuch. Therefore, presumably no exceedance actually exists but only the utilization of the permissible exceedance under §19 (4) Baunutzungsverordnung. Furthermore, the Thüringer-Bauordnung does not even provide the possibility to build without approval according to §61 if stipulations are not to be complied with, so your information regarding the content of the preliminary approval of deviations (if it exists at all) is incorrect.

First try to obtain reliable information about the exact planning (site plan, elevations, exemptions, deviations) and the planning status (building consultation, building inquiry, building notification, building application, building permit) and formulate as precisely as possible in which rights you see yourself violated.

First of all, thank you very, very much! I obtained the information as a direct neighbor from the interim inspection of the deviation granted in advance upon request pursuant to §66 Thuringian Building Code from the floor area ratio set as the "maximum" in the development plan of 0.3. (My assumption of the exemption proved to be incorrect.) This was done on my own initiative because the builder raised the site and placed 2 base slabs as well as 2 garages on both boundaries. (He does not yet have a building permit and is currently trying to obtain it based on the deviation granted in advance within the simple building notification procedure.) (He complies with the setback distances but omitted the terrace in the deviation application.) I see our rights violated in that our publicly-law protected neighborly interests according to paragraph 1 §66 Thuringian Building Code were not sufficiently considered and we were not notified before the deviation was granted as stated in §69 paragraph 1. So our signature was not obtained either. Furthermore, I see in the application of §19BauNVO that with the deviation granted of +50% => +0.15 = 0.45 the upper limit of 0.4 for the measure of structural use according to §17 for general residential areas, which the development plan specifies, is exceeded. Since this is not excluded in §19. Especially because, only through the granted deviation a semi-detached house was made possible by the size and thus a kind of change of use of the property size. (Applying the floor area ratio of 0.3, a normal house with terrace, garage, driveway, and ancillary facilities, as in the neighborhood, would have been possible! All plots are quite large. He already has 2 smaller adjacent ones where he could have built a semi-detached house. He has now already built a single-family house on one and wants to build another semi-detached house on the other and then sell privately. Whoever wants that must buy a larger plot.) => The floor area of our house – we have been living newly built directly below for 5 years – now lies topographically about 2 meters lower than that of the builder. His development plan was later planned directly adjoining ours. We and our neighbors therefore feel impaired by the large building volume. Since the development plan was designed therefore also deliberately more open (floor area ratio 0.3) and we see the deviation ("can" but does not have to) for our directly adjacent lower row as inappropriate. In our opinion, this also violates the principles of the more open planning to protect the lower neighbors from too dense development. Since the deviation now causes exactly the opposite. Does shading – before the authorities – even count as an impairment? But that we now sit behind a wide front like a "prison yard" caused by the large building volume made possible by the deviation: 2m lower + 9.5m max. building height = 11.5m, weighs at least as heavily for us. Moreover, in heavy rain events, damage must be expected for us as the lower-lying ones due to the increased sealing.

Deviation granted upon application under §66 Thuringian Building Code from the floor area ratio of 0.3 set as the "maximum" in the development plan. (My assumption about the exemption turned out to be incorrect.)

Sorry, I don’t understand. Without the original document, I can’t follow this. Did you read the justification?

He does not have a building permit yet

Inform the authority immediately and request written action for building supervisory intervention.

our publicly-law protected neighboring interests

Which ones? As I have already explained, these do not exist in your case; at least not on the basis of the floor area ratio determination.

the upper limit

... must be observed by urban planners when drawing up a development plan. They have done so. So forget §17 of the Federal Land Utilization Ordinance.

Especially because only through the granted deviation a semi-detached house was made possible by the size and thus a kind of change of use of the plot size.

There is no planning law protection for neighbors outside the scope of "your" development plan for you. And therefore no obligation for neighbor participation in planning law exemptions either.

for the protection of the lower-lying neighbors

On what do you base this conclusion? Is it stated like that in the justification for the development plan? Then a visit to a lawyer is worthwhile.

Does overshadowing – in front of the authority – even count as an impairment?

Yes, but as tolerable if the legal setback requirements are met.

But that we now sit behind a wide front like a "prison yard" caused by the large building allowed through the deviation: 2m deeper + 9.5m max. building height = 11.5m weighs at least equally heavily for us.

As long as building code law – especially the setback areas here – is complied with, you have to accept that.

Moreover, in the event of heavy rain, damage to us as lower-lying residents would have to be expected due to the increased sealing.

Hypothetical damages are not enforceable. Take photos of the existing situation and claim damages if actual damages have occurred.

Sorry, I don't understand. Without the original document, this is not comprehensible to me. Have you read the justification? ->I was only shown the site plan with areas. ... city planners must consider this when drawing up a development plan. They did. So forget §17 Land Use Ordinance. -> I mean, even when granting the deviation, it should have been max. 0.4? There is no planning law neighbor protection for you outside the scope of "your" development plan. And therefore no obligation for neighbor participation in planning law exemptions. -> The laws and building regulations don't only apply to development plan areas, do they!? Yes, but must be accepted if the distance regulations are complied with. -> That doesn't make it any better. Hypothetical damages are not enforceable. Take photos of the existing condition and claim damages if actual damages have occurred. -> Then the BH (building permission) is gone. And people who bought privately without warranty are ones the neighbors actually don't want to sue.

Are there any alternative possibilities?