Mike has an attic full of loose-fill insulation and needs to renew his ceiling. But he doesn't dare take the old drywall down because of all that insulation. So how do you put new drywall over the old?
First locate the ceiling joists by the nailing pattern, and mark the ends of the joists on the walls an inch below the ceiling. That way you can find them as the new drywall covers all your clues. If you don't want to write on the wall, mark them with little pieces of painters masking tape.
With marks on opposite walls you can snap a chalk line across the new ceiling showing where the nailing base is located.
Stagger the new drywall to overlap the old, no drywall edges lining up from one layer to the other. Remember that the original ceiling was always put up before the walls, so if you want to match the nailing pattern and you measure four feet from the wall, your new mark is a half inch past the existing nails. You may want to trim some sheets accordingly to avoid nailing too close to the edge of the joints. Put extra nails around the edge of the room because the walls are no longer supporting the ceiling.