The Sims 3 recieved a new patch today, check out the download link and patch notes below.

Patch Notes

• Added a new spiral staircase object.
• Added a new ladder object.
• Added a new modular arch object.
• Added a set of new Stilted Foundation objects.
• Lots can now be partially placed on water.
• Holding down the Alt key while dragging out a foundation will now make a single step height foundation.

You can find the download link to the patch here.