This is what I was referring to: http://forum.thesims3.com/jforum/posts/list/390/604090.page#9768812
@busanfaa: Does your house have a foundation.
I had the same problem...I was building a 2nd floor on my sims house and when I went to save, it crashed and lost all of the changes. The next time around I saved every few minutes (obsessive like) and figured out that it was crashing after I built my custom roof. Then I went back and did a few pieces of the roof at a time and found that it only crashed after I used the Mansard style roof. I don't know if this is a common bug or if it is just something unique to my PC...but as long as I'm not attached the the Mansard roof, I'm ok for now....but it would be nice if it was an option 🙂
mine does the exact same every time i try to add another floor it crashes out... hopefully it's fixed in the next update
