Legal assistance with inheritance division and extensions

Questioner

We are going to build an extension. We want to build on the boundary wall. The wall is exactly on the boundary and is now 2 meters high, will be 3 meters. The neighbors absolutely do not want to cooperate. Can we realize our wall on half of that wall? We have a permit from the municipality. In addition, we have to build around their protruding fascia (hangs over our side of the property line but has expired). The neighbors demand that there be 17 cm between them to maintain the fascia, which we of course find ridiculous. They can easily get to it with a piece of sandpaper and a roller if we already maintain 5 cm. Is there anything in the law for this?

Lawyer

You may build against the shared wall and attach anchors etc. up to half of the wall, but you may not build on the wall (not even on your own half). There is no minimum distance to the neighbours' property, you may build up to the fascia board, but you may not make any attachments there.