2D Floor Plan
The most efficient and quickest way of creating floor plans from an existing building, especially old ones, is by utilizing 3D scanning technology. It gives you all the details in one go! No need to go back and add information like windows' height, ceiling heights, and lots of other details that could be missed in conventional methods.
Do not think of using any other methodologies than 3D Laser Scanning when you are revovating a house. Get the drawings done proprly as they are the base of any other work to be carried on.