Garage extended or additional carport

Hello community!

I have newly registered here because I need help with the planning and implementation of a garage extension or the addition of a carport. I hope I have chosen the right subforum.

Regarding my background: Two years ago we bought a detached single-family house. On the property, there is a prefabricated garage that borders neighbor A’s garden boundary. On another side, there is a carport adjoining neighbor B. Both are reached via a private driveway. My wife parks her car under the carport, I park mine in the garage. Until now, everything is/was fine. Now I spontaneously bought a motorboat (because of a very good offer), which is on a trailer. I initially rented a parking space 15 km away from my residence. Since behind the garage there is just a rampant jungle and I would like to use the space as well as park the boat at the house, I wanted either to extend the garage or build a carport behind it. Unfortunately, I cannot set up a parking place beside the garage or elsewhere.

My plan: The boat trailer is 6 m long, the car garage is about 5.60 m. My first idea was to remove the back wall of the garage and, for example, extend the garage with aerated concrete blocks. I have basically given up on this idea because something like that without an architect, structural engineer, building authority, and the neighbor’s consent (since it’s over 9 m) and probably even to build it myself is either impossible or very difficult to realize. My new idea is to install a second sectional door on the back wall of the garage. Then build a carport behind the garage. That way I could push the trailer through the garage under the carport. To illustrate, I have created a few sketches here:

Current status: behind the fence borders the neighbor’s garden


Plan with the carport behind the garage:

View from the back:


So now to my questions:
Is it possible to remove the back wall of the garage and install a second door or would that be too unstable? Do I need permission from the building authority for the change?

I will probably also need a building permit for the carport. But no (written/official) consent from the neighbor, right? I think the maximum length of 9 m refers to a “continuous” garage? If I were to buy a prefabricated carport for self-assembly, I wouldn’t need an architect/structural engineer, would I?

I would be very grateful for your help.

Best regards

Google "Grenzbebauung NRW". You are allowed to build up to 15 meters at the borders, with a maximum of 9 meters in a row. You already have a carport of 6? meters, garage 5.60... that makes 11.60 meters together. So you can extend 3.40 meters more to one side or the other.

I will probably need a building permit for the carport as well. But no (written/official) consent from the neighbor, right? I think the maximum length of 9m refers to a "contiguous" garage?

The regulation does not refer to individual components, but to the respective boundary of the building plot. So the lengths are added together; otherwise, the regulation would make no sense, because then everyone would build their plot completely with components each a maximum of 9m long.

If the building authority is not in deep sleep, you need an appropriate building encumbrance from the neighbor for the construction project. If the other individual garage is 6m long, the boundary development results in 6m existing + 5.6m existing + 6m new carport = 17.6m. Permitted are 15m, therefore you need a movable building encumbrance on the neighboring property within the old/new boundary development of L x W = 2.6m x 3m.

Best regards Dirk Grafe

Thank you very much for your answers! Then I misunderstood. I thought that a maximum of 15 meters may be built on a border. Yes, the already existing carport is about 6 meters long. If I understood correctly, I "only" need a building encumbrance and a building permit from the adjacent neighbor where the new carport is to be built in order to realize the construction project? Would the property also have to be surveyed in this case? I have heard that vehicles with green license plates (which the boat trailer has) are sometimes subject to different rights and regulations, or does this not affect building law? My other alternative would be to build an uncovered parking space behind the garage, for example, just a paved area and possibly some kind of removable tent roof. What is the legal situation there? And is it even possible to remove the back wall of the garage and install a second gate? I hope I am not overloading you with my questions, but I am really a beginner in the field of building law. Thank you very much

If I understood correctly, I only need a building encumbrance and a building permit from the adjacent neighbor where the new carport is to be built in order to realize the construction project?

You understood that correctly.

In this case, would the property also need to be surveyed?

It depends.... But I don't want to make it too complicated, since in 99% of cases no boundary survey is required. However, since you are building on the boundary, a building staking out is strongly recommended. Because of the building encumbrance, you have to involve a publicly appointed surveyor anyway.

Or does it not affect the building regulations?

No. The building authority does not care what type of vehicle is stored under the roof.

A kind of removable tent roof. How does it look legally in this case?

Grey area. If it doesn't bother any neighbor. Otherwise, your neighbor could keep records of how often and how long the tent roof is up or not and report a building violation. If you never take it down, it would be considered a permanent installation and could be subject to approval.

And is it even possible to remove the back wall of the garage and install a second gate?

This question can probably only be answered by a structural engineer on site.

Hello and thank you very much for the detailed response. I think that regarding the plan to extend the garage over the carport annex, I have now ended up with a simple parking space behind the garage. I would then rather just create an area with grass pavers or possibly cobblestones behind the garage and also forgo the tent roof. Do I then have to get this parking area approved or "registered" anywhere?
Best regards