The Sims 3: How do you build a garage?

On the Sims 2, how do you delete a wall or garage or whatever else. i go into build mode, but it wont let me.. i never built the house on there myself, but shouldnt i still be able to make changes to it?

• Answer:

  I had Sims 1 - In that one you had to select the tool (Door tool for doors, window tool for windows, wall tool for wall). It was best to remove windows, doors and wall hangings (furniture) before removing a wall. I believe holding down Shift key lead to walls being formed in a rectangle and I think it was holding down the Control Key (Ctrl) while using the wall tool over the existing wall to remove it. I think most of that carried over to Sims2.