Add the driveway piece and add the matching driveway extension piece to the inside of the garage and add a garage door. Add one block of foundation to the extra tile inside the garage and place a set of connecting stairs and a door. This will make it possible for Sims to enter the garage from their home. Add some wallpaper to the walls on the inside and some wall covering that matches the rest of the house to the outside. This is also the time to add windows and a back door. Also, be sure to add a roof. You have now completed building a garage with a foundation in The Sims 2. Now, a car can be placed in the garage and any other desired items.