It looks like lumber above the box so I say it will be okay. But one screw is not enough. You might have to remove the screw and turn it so you can get at least two screws into good thick lumber. This by far is the easiest way to get this job done.
Not exactly a fan box, but okay for this old work.
That location looks like an easy swap to a fan rated box though. The box looks like it will come right out and allow very easy mounting of the correct box.
Not exactly a fan box, but okay for this old work.
That location looks like an easy swap to a fan rated box though. The box looks like it will come right out and allow very easy mounting of the correct box.