Procedure for renovation measures in the basement unclear

Hello,

we own a semi-detached house and have had one room too few since the birth of our daughter (third child). Slowly we need to make sure that she gets her room or that our two boys each have their own room again and no longer have to live in the same room. In theory, we could share a room upstairs and create the same floor plan as our neighbors, but then we would have three tiny rooms of about 10m² each and we don’t want to impose that on our children. Since we have a basement, we thought we could move our bedroom there and thus have three nice children’s rooms on the upper and top floors.

I have attached the floor plan once and tried to draw on the plan with my immense Paint skills. We would like to share Basement 3, extend the hallway wall (is that simply done as drywall?) to create a storage room on the left side (which is currently in Basement 1), move the wall a bit on the right (do you need a structural engineer for that?), to separate bedroom and office (for which we would then need another basement window – is that even possible?), and build an additional wall to create an extra bathroom (we had already gotten a quote for that about 1-2 years ago, so we can roughly estimate that).

We honestly have no idea how to approach this issue. Is any of this even allowed to be done in the basement? Do you need an architect for that? How do you best find a good one? How can you best estimate the costs, since we would have to finance most of it ourselves? How do you find reasonable craftsmen if you can barely lay laminate yourself?

Many thanks in advance for all tips.

Best regards
Sebastian

Would choose the mini rooms as long as they are small mine are only 12 too

Hard to say because the plan of the floor above is missing, but the wall could certainly be load-bearing. You definitely need a structural engineer here. Are the basement windows suitable as an escape/rescue route? Due to the additional windows, a building permit might be required, right? Then you also cannot avoid involving an architect as well as a structural engineer. I would definitely prefer the mini rooms. Much, much easier and much, much cheaper.

Your plan is already quite complex to implement. Also consider that a bathroom in the basement, for example, requires a lifting system as additional technology. What if you take the "small" children's rooms and convert basement 3 into a playroom for the children? Possibly divide it further with a drywall partition into a boys' and a girls' playroom. Here, toys could be left lying around, which is rather suboptimal in a 10m2 children's room.