How do you build a basement in the sims 3 ps3?

Answer 1

I dont think you can...

I dont know if this works, but you could try going on landsculpting, lowering the ground level, making the ground level even and then try and put walls on it.

I just made that up right now, I dont know if it works... a basement is a good idea, I never thought of that. You could always build a garage if it doesnt let you build a basement. :)