okay so i built a house for starlight shores, and it needed a man cave. I could place the stairs cause a message said cant place stairs inside foundation. I had also had a "basement" garage in the house. (i believe the sim supply on you tube has a video for this) ans techniqually, the garage is outside the basement. Simply make a drop in floor. (constrainfloorelevation false* cheat is needed) and then add you stairs on the lowered not foundationed floor and bingo! You get a true basement.

This is an old thread but no one seems to have posted a "stairs through foundation" solution without using cheats, so I'm adding it here now. Hold SHIFT when placing stairs from ground floor level (not basement level or ground level, but **ground floor** level). Stairs will go down from floor to floor, no worries.

Thank you so much ... I just did it and it worked. I'm so going to have basements in all my pre-build houses now :D

My thanks, too! With this instruction, I feel I might actually be able to place basements in existing homes. My overly crowded Sims will be thankful too.

Either I'm doing something wrong or this doesn't work anymore. When I click to place the stairs while holding SHIFT, mouse disappears and nothing happens.

I was gonna try the long text method from the previous page, but honestly, it's too complicated for me :/

wow thank you i have been trying to find a fix

Same with me. Actually it's much better to
1. build a basement, then
2. add a staircase down,
3. build the foundation around and at last
4. fit the connection staircase to the one down to the basement.

If you don't wanna do that I have a tutorial a way to do it with the constrainfloorelevation cheat here: http://www.youtube.com/watch?v=xcfj...ture=plpp_video

I've tried placing stairs while holding shift with and without the foundation. I received two messages : cant place stairs inside foundation ( AGH! ) and terrain too high. Which confused me.

I tried the constrainfloorelevation false/true trick but I still had thephantom foundation error ( AGH! ) I think the problem is the second floor?
ok I moved the second floor back....the roof? ( AGH!)

At least I can build half walls now. -sigh