I thought I didn't know how to use terrain tool. I had this issue when terrain tool was updated by patch last year. Since that time, I don't place foundation when building my sims family home. There's no problem with building a basement without foundation.
Just wanted to further update. I was playing around a bit more on the Blue Velvet lot that I showed the pictures of earlier and I found if I lowered the foundation, added the basement and then raised it again the foundation will apply evenly to the full building, even where the basement goes out to the outer wall of the building. I had wondered if using the 'flatten terrain' tool would fix the problem, but it didn't when I tried it. The downside of this solution is that all stairs are removed from the patios/porches and have to be added back (which is more an issue if you are adding a basement to an existing build as if you do it when you are building, you just need to add the stairs in later). So not necessarily ideal, but it is a work around if you are having this problem.
Thanks and regards,
Jennifer
