So basically, the other tutorials for Sims 3 on how to make a split level explain how to make a level of the house lower than the rest –(or equivalent to 4 clicks)—
In my tutorial, I will show you how to build a split level equivalent to 8 clicks, though part of it goes slightly underground.
There is no custom content required, and I have tried to take the screenshots as simple as I could.
Hope this helps anybody who was curious on how I accomplished this feature in one of my projects.
And just to let you know, the tutorial is in a Word Document.