Here is another tutorial, maybe it will work better for you. http://simsasylum.com/tfm/index.php?/to ... oundation/ You do need to be registered there but it is a pretty good tutorial.

Hey guys! I did it!

I don't know why it worked this time, but after trying every tip and magic trick I could find online and here, I finally managed to get the stairs work and they landed nicely and neatly right down all the way to the basement. Hooray! It did took a long time, some frustration and many altered attempts with curse words, but in the end - I now have my desired gloomy basement for my sims to have fun with their band! Thanks everyone! 

PS. Yeah, JohnL83, I was astonished how much space you need to clear out for the stairs to properly fit in. They totally complain about every damn thing, like the lamp above or what not. Geez. Basic Sims.