I did something similar. I'm building what I call my "Inverted Fortress": I'm at eight floors in this screencap, but am up to thirteen floors on my computer at home:
http://i.imgur.com/SoRXcjl.jpg
It's a quite challenging resource-wise due to the increased need for wood with each additional floor. Just the requirements for the surface area of each floor is incredible:
- Floor 1: 27
- Floor 2: 55
- Floor 3: 91
- Floor 4: 135
- Floor 5: 187
- Floor 6: 247
- Floor 7: 315
- Floor 8: 391
- Floor 9: 475
- Floor 10: 567
- Floor 11: 667
- Floor 12: 775
- Floor 13: 891
- Total: 4823
That doesn't count the requirements to build the stairs and posts needed!