Expand the house or a crazy idea

Hello dear forum community,
I have had a crazy idea (???) in my head for a few days now.

We built our little house in 2015, and everything is basically perfect for us. However, we had another child in 2017 and are now five people. Unfortunately, our house does not have three children's rooms, so the two girls share a room. This might still work in toddler age, but I fear it won’t work forever...?

Since my dad and I have done a lot of work on our house ourselves, we tried to come up with some ideas. Unfortunately, the floor plan doesn’t offer many options, and basically only an extension is possible.

Unfortunately, the development plan specifies a building plot. This has already been fully utilized in all directions. Except to the north, we still have about 8 meters of room... currently, our garage + carport is standing there.

I could imagine an extension on top of the carport/garage here...

For that, the current ceiling made of rafters and battens would have to be replaced with a concrete ceiling (filigree ceiling?). I would like to keep the carport and garage as they are... only a construction on top of them. The garage is located 1 meter outside the building plot, so I couldn’t build over everything. But an area of about 8 x 6 meters would still be created. Then everyone would have their place in the house...

My questions regarding this:

1. Would something like this be feasible, or is such a building project not possible due to building regulations?

2. Could the garage/carport be retained, or would this be impossible due to statics? The concrete ceiling would have to be placed on the already built garage.

3. The bathroom as well as a newly created room would then only have light through (large) skylights – is that allowed?

4. What would be sensible/feasible in terms of heating? The utility room is located right next to the carport... we have a gas boiler installed.

5. The current "parents’" room would then become a large "hallway"... what could one make out of this?

I know there are no 100% answers to these questions... I’m more interested in the essential points I might not have considered and that could make this a crazy idea...

I would say: crazy idea. Even if that were approved, it would probably become very, very expensive. Easily 150k. I estimate that due to the massively increased loads, the carport and garage would have to be rebuilt from the foundation, then the roof extension... It would probably be more economical to sell the house and move into a bigger house. Apart from that, the result is not good either. The passage room is wasted and the two new rooms are actually too small. Lots of hallway for a lot of money.

What does the floor plan of the [EG] look like?

I also think it is a crazy idea. In the end, you lose a nice room and gain two smaller ones.

I would say: crazy idea. Even if that were approved, it would probably become very, very expensive. Easily 150k. I estimate that due to the massively increased loads, the carport and garage have to be rebuilt from the foundation up, then the roof extension... It would probably be more economical to sell the house and move into a bigger one. Apart from that, the result is not good either. The walk-through room is wasted space and the two new rooms are actually too small. Lots of hallway for a lot of money.

The house has received a frost skirt at least 1 meter deep and the floor slab is placed on that... but the garage also received strip foundations at least 1 meter deep...

Regarding the roof extension, I don’t really see the problems. We did that completely on our own for the house.

Wood and crane cost 3,600 euros... we straightened the roof truss ourselves. The roof tiles for the entire house were 4,500 euros... battens and roofing were another approximately 2,000 euros... so about 10,000 euros for the house... should be about the same for the smaller extension.

We are also talking about Brandenburg here... I built/had our entire house built for 150,000 euros. ;-) My brother added a floor to my grandparents’ house. That was one floor with 115 sqm and he paid about 100,000 euros.

The two new rooms would be about 3.80 x 4.20 meters = just under 15 sqm excluding walls. So as big as the current kids' rooms... and I actually don't find them small... I had 10 sqm as a child...

As you can see, I won't give up that quickly....

A move is also on the what could be possible list... unfortunately, we like it very much where we live... location, neighbors, property... so I would only make that move reluctantly...

What does the floor plan of the ground floor look like?

I also think it’s a stupid idea. In the end, you lose a nice room and gain two smaller ones.

I lose the master bedroom with almost 13.6 sqm and get two with 15 sqm each instead... still annoying... that’s why I’m asking if something could still be done with it...?

Why would you want to extend the corridor all the way to the back in the extension, instead of having the back room span the entire width?