ᐅ Facade insulation on a semi-detached house: what and how approval from neighbors is required

Hello dear forum members,

I have some questions regarding the renovation of my semi-detached house that I am planning and hope you can assist me with.
I want to have my semi-detached house insulated according to KfW standards.
According to the declaration of division, the two semi-detached units are completely separate from a legal point of view.
However, in my case, the roof needs to be extended by about 2 to 3 rows of tiles so that the insulation is also protected from above.
At the same time, the roof gutter between my property and my neighbor’s must be adjusted so that rainwater can continue to drain properly.
Additionally, the plasterer recommends installing insulation extending slightly (about 50cm (20 inches)) beyond my property boundary onto the neighbor’s side to avoid thermal bridging.

In which cases do I need my neighbor’s permission? What should such permission look like?
Is there a template letter available in this forum that I could use as a guide for wording?

Thank you in advance for your possible answers.

Thanks

Simply asking the neighbor (once you know what is legally required) if they might also be interested in insulation? This way, it becomes a bit cheaper for everyone... The scaffolder comes for the setup and dismantling for the entire house. The roofer as well. The plasterer... and so on...
Of course, the neighbor needs to have the necessary funds...

At the same time, I would provide a calculation of the planned energy savings...

In which state/province is the facade being done?

I have already spoken with the neighbor as well.
He is not interested in insulating the facade. He believes that insulation inevitably leads to mold problems in the house. ))

Built in 1985 in Baden-Württemberg.

May I ask how much the complete insulation costs and what the current annual heating costs are (preferably excluding hot water production)?

You are not allowed to extend even the smallest part of the insulation onto your neighbor’s property without their consent.

“The Higher Regional Court of Karlsruhe has ruled that thermal insulation must not extend onto the neighboring property, according to the ARGE Baurecht.”

So, if they agree, get it in writing and ideally have it recorded in the land register. Otherwise, a future owner might come along and demand that it be removed from their land.

The insulation, including the roof extension, costs 21,000.
Heating costs are currently around 1,300 € per year.

Thank you for the information.
Do I also need a land register entry if it only concerns the issue of the "roof gutter" for rainwater?
The 50cm (20 inches) from the neighbor is actually just a recommendation from the plasterer. However, it is not mandatory!