Cristiano,
I would think you would want 2.5 m (8 feet) for the ground floor ceiling to make the "loft" useable as far as head room goes. That should give you enough height to build the KR. You will need to take the project outside to turn it upside down or back rightside up but I had to do that with a 10 foot ceiling. Mark Langford build his KR in the basement and I'm guessing he had a 7.5 to 8 foot ceiling. Larry Flesner
