Anyone in his garden Build a garden house wants to, he shouldn't just do it how he wants it, certain things have to be considered here. Usually you don't need one building permit.
Building permit depends on the volume of the room
However, this depends on how big the house is and whether a certain volume of space is exceeded. If this is the case, the building must be approved. How much space you have depends on the federal state and can be requested from the municipal office.
No base plate
Also, the garden house must not have a concrete slab as a floor finish, this would also require approval.
Note the distance to the property boundary
You also have to take distances into account. A garden shed must be three meters from the property boundary. If you build directly or closer to the border, the house must not be taller than three meters.
But here, too, the regulations often differ and should be inquired about before construction. If you simply build instead and the neighbor takes action against it because the construction is a violation, the house must be torn down again.