TUTORIAL :: Adding basements to existing houses with foundation :: No demolishing necessary!
STEP 1: Spartan wants a basement, this looks like a good spot! Unfortunately the house is already built and furnished, but that can be easily fixed. No need to demolish whole parts of the house ...
Thank you very much for sharing gorgeous tutorial, I still didn't tried something like this, but I bookmarked this thread for any case - it also has useful info for the sunken rooms! :)