Most of the time this can be fixed pretty easily. The door will just have to be leveled out and Rehung. Far as what causes this problems there are a few different things 1 is the bottom piece of wood that runs along the whole bottom of the door usually a 2 by 6 piece of lumber will over the years from the elements start to sag in the middle causing it to rub the floor of the garage when it is closing. Another Thing that can cause this problem is a bent or damaged or even a hinge that is falling apart because it needs to be replaced. When a one Piece door hinge gets distorted or starts to break down it will put the garage door in a totally different position than it was when it was originally hung in there for will start to rub in different places that it did not used to.

adjust a one piece wood door

The best way to be level and adjust a one piece wood door is to have the door in the down position and put some kind of wood shims underneath the bottom of the garage door where it may be rubbing. then you will have to remove the 3 or 4 screws that attach the hinge to the actual garage door and then drill new holes for the new position of the door and then once that it has complete the door should open up and close without rubbing. Not every instance would allow you to do this since you have to actually move the door up about an inch at least so you will need to consider the top of the garage door and where it hits when the door is closed.

bottom piece of lumber…

Now if your bottom piece of lumber on your wood one piece door is sagging in the middle then you might have to replace that piece of wood which is kind of a pain to do but it can be done and don’t expect a garage door company to do it very cheap because there’s a little bit involved and ripping apart old wood can make matters worse and then they would have to replace other wood on the door that they did not plan to so it can kind of turn into a big mess. One consideration would be converting to a sectional roll up garage door if you can, or you can replace your wood one piece garage door with a metal one piece garage door that looks exactly like a sectional roll up door the only difference is it does not roll up it will act and function just like your wood one piece garage door but look exactly the same as a sectional garage door when it is in the down position because sometimes your garage cannot accommodate a sectional roll up door.