We get a lot of questions on our blog about the doors to our barn. We actually made them from recycled 3/4 inch barn flooring from the Cardington Barn we tore down last summer. When the huge doors needed for our new barn were going to cost over $1500 for just one pair - we decided to make our own from some of the old flooring we had taken out of the old barn.
A hint when working with old barn wood when your going to re-purpose - dont spend a lot of time with sanders or planers. They are hard to use - and easy to ruin with nail fragments. Instead - we use a fan nozzle on our pressure washer - and simply clean away years of grime. It leaves behind the beauty of the old wood and once it dries out in a day or two - you can stain or paint or just leave it natural. We ended up making 4 doors for our barn at a cost of about $20 in screws.
One other hint - pre-drill everything when working with old, hard oak. Your drills and screw bits will thank you :)
They have been up now since early this year and should last for years!