Foundations are used to raise the level of the main floor and can be used over uneven terrain. In The Sims 2, unpatched versions of The Sims 3 base game, and The Sims 3 for console, foundations are required for the construction of basements.
The foundation tool is used by clicking and dragging an a square area on the terrain. There is also a diagonal foundation tool.
Players can choose either a decking foundation, an elevated foundation, or a brick foundation.