Sims 2 Building Question?

I am trying to build a house with a connected garage, but it won't let me connect the walls to the foundation of the house. I had planned on having a small set of stairs coming down from the foundation of the house into the garage, and I don't want there to be a gap between the house and the garage. I have already tried the moveobjects cheat but that didn't work. Does anyone know how to do this?