Extension of garage using cold winter garden - permitted?

Hello everyone,

we are planning to open the back of our double garage and extend it with a cold conservatory.

But before we shoot ourselves in the foot with the responsible authority, better ask first.

The initial situation is as follows:

The mentioned double garage stands on one side on the property boundary and adjoins the house on the other side. Behind the garage there is a small courtyard, which is flanked on the left side by a wall extending from the garage and on the right side by the house wall. To the rear, this "courtyard" is open to our garden, which is on a higher level, but only partially visible – and currently not accessible by car. So far, this courtyard has been completely unused and even after redesigning the garden we could not find a meaningful use for the last remaining "triangle".

Now it would be obvious to partially remove the back wall of the garage (which would be structurally possible) and roof over the area behind the garage with a cold conservatory, thereby creating additional parking space. So far so good.

However, I recall in connection with another garage project that a garage on the property boundary may not be higher than 3m or that the associated wall on the property boundary may not be longer than 9m.

As of today, however – and this is where it becomes interesting – the garage already has a depth of 8m and the wall on the property boundary, i.e. in extension of the garage, measures an additional approximately 5m.

So we have 8m garage (height 2.9m) + 2.5m wall (height approx. 2.7m) + 2.5m wall (height approx. 1.5m) => making a total length of 13m.

The conservatory builder said that this would not be a problem at all. Even if the boundary structure is 4m too long, the existing wall would have guaranteed protection after the 30 years it has now stood. Therefore, building a roof, constructed as a cold conservatory mounted on this wall, would be no problem.

So my question now is, is what we were told about this legal protection true or do we risk a later removal?

For the sake of completeness, it should also be added... Our neighbor would have no objections since he would not see anything of the extension anyway. His side of the wall is covered over 6m by his own garage and the remaining 7m he has planted with a tree hedge about 6m high – which we also support equally and in our own interest.

Non-conforming use protection does not apply because you want to change the existing structure. And this change must comply with current regulations. Specifically, the following applies here

§ 6 Landesbauordnung
Setback areas in special cases
(1) Within the setback areas of structural installations and where there are no separate setback areas, the following are permitted:
1. Buildings or parts of buildings that have a wall height of no more than 1 m,
2. Garages, greenhouses, and buildings without rooms for habitation with a wall height up to 3 m and
a wall area up to 25 m²,
3. structural installations that are not buildings, provided they are not higher than 2.5 m or their wall
area does not exceed 25 m²

Roughly speaking, you are above the limits, meaning the buildings lose their privileged status and require setback areas. I would discuss with the building authority what options you have (e.g., easement or neighbor consent).

Thank you, that already helps me a bit further.

It's a pity, I thought the existing right of use would not be affected if I do not change the stepped wall and only use panes as the lateral closure of the conservatory.

But before I go to the building authority, I am still interested in the following....

... the garage wall on the boundary is almost 25m². Are the 25m² fully counted despite the neighbor's garage standing at about 18m² on the wall? From the neighbor's perspective, the garage (without the extended wall) only occupies about 7m² in terms of calculation... Or does the principle boundary construction = boundary construction simply apply?

Thank you very much in advance!!

Or does the principle of boundary development = boundary development simply apply

that's right! Maybe the neighbor will tear everything down in 15 years and build the garage on the other property boundary, then your building would suddenly no longer comply with the applicable building regulations.

If the neighbor agrees, your project should not be a problem, it just costs more fees.