House Plans

The set command won't help you, if I understand it right , because it creates a solid figure, i.e. a cuboid or cube and not a room/space filled with air.
You could use the set command for a wall, or for the solid figure, as you wish.

A room 8" x 8 " (my problem are the inch measurements, I would simplify it with 80" = 1 m, so for your room
you need different parts to put together.

Or you think about to use the inch measurements by using the block measurements 1 block = 0.5 m.
For me it's difficult to implement building plans with inch measurements, as the dimensions unfortunatley do not exactly match the meter measurements.
I had to convert the building plans for myself.
The grid could help you, if you build your walls with wooden beams more exactly.

If you're trying to make a "real" or "this-worldly" building, you'll find out very quickly that you must go more on feel than on specific dimensions. Real doors are 28x72 to 32x80 (int) and 32x78 up to 36x80 (ext) inches, and if you look at a door, it "seems" right because that's what you've seen all your life. Rooms "look" right for the same reason, even though they might be anywhere from 8x8 to 12x16 feet. Back when I started playing (5 yrs next month), I used blocks almost exclusively because they fit together (and we didn't have the tools for placing wood yet). Now, I build mostly with wood and stone/metal-faced boards (pnb). I'd recommend that you practice with that. Your favorite tool is the crowbar, and whenever you don't think it "looks right", tear it out and redo, redo, redo. Another suggestion I've found helpful is to start with the floor and make it a bit oversize. Then put in the furniture that you plan for that room, and finally the walls. Nothing like building a rooming house with rooms too small for a bed, table chair and dresser/closet! (Yeah, been there!) Hope this helps, and I'll go back to lurking

• I would never feel about dimensions, not in modern buildings, maybe in medieval ones s little bit. We have several houses built 1 to 1 with original building plans, very very exklusive houses. But what I meant you have to fit the building plan a little bit if you want to use inch instead of meters (for me, I cannot convert very well). The ingame furnitures are a little bit too big, so maybe you have to build your own ones.

Red said 1 block is approx 60cm.

If you want a room to be 8x8m you could make a plank 8x8x0.25m and place it. Then add walls.

If you want several rooms you could make walls and ceiling with some space in between and blueprint the whole thing to use it modular in your house.

I don't know meters to inches though, sorry