The house I have

I am planning to add on to the house I have. I decided to do a reasonably good plan of the house I have (in x/y, not so much in z). Here are the drawings:

The existing house is 32 feet from front to back (not including the porch) and 24 feet wide. Thus, the footprint of the house itself is 768 ft^2. The max allowable coverage for the lot is 30%, which comes to 2160 ft^2. The porch is 6' deep (or so) * 24' wide, so it adds 144 ft^2, thus the existing house uses up 912 ft^2, leaving 1248 for the addition. My thought is to add on 1200 ft^2 -- 30' deep by 40ft wide. Add a back porch & it is all used up.

Basement level. This is ground height in the back, underground in the front. It's just one room, with crawl space under the front. I forgot to put in the door in this drawing, and decided not to put in the (pitiful) windows, so it's even more boring than in real life. All the things that look like windows, etc, are from the floor above. For some reason, the program put them in. It is 24 feet across & 14.5 feet from the back of the house to the wall.

The main level: The thing that looks like a room without doors near the back is the staircase. The smaller thing that looks like a tiny closet is the chimney. The small room in the back is the bathroom, the big room in the back is the kitchen. I am using the big room in the front as my bedroom, eventually I plan for it to become the dining room.

The upstairs. The room without doors is the staircase again. The areas that come off the side of the hallway at the back & the room at the front range in height from about 4.5' to 2.5' -- the area under the eves, I guess you could call it. The areas at the front, side & back, with windows, are dormers.