I built a house, but when I send my Sim upstairs, there is no upstairs actually registered. They go up the steps but they just float on top of the FIRST story/floor. When I send them from the upper floor to the lower floor, they do not use the stairs, rather they sink down to ground level of the first floor. I've tried deleting the upstairs and rebuilding it, but the same thing keeps happening. I've also tried turning on "constrainfloorelevation false" and levelling the floors in case they are out of sync with eachother, but it doesn't seem to be doing any good. I tried searching for solutions to this problem but can find nothing in relation to it.

ETA: Uploaded a video of the occurrence in case it's helpful: http://www.youtube.com/watch?v=zkxQhY_WIeU

This is most likely nothing to do with your house. Go look here under weird behaviour: http://www.modthesims.info/wiki.php..._3_Game_Problem

This can happen when you've moved the sims around, too. Try doing "resetsim (firstname) (lastname)" on them.

Resetting the Sims worked. Must have been from when I moved them out of my way with moveobjects on. Thank you HP!