I have a 10 year old shed for my lawn tools, that is 2X constructions, with standard particle board siding. While the outside was painted immediately, the inside of the siding was left unpainted. The doors are basically a sheet of siding with 2x4 around the edge of each door and in the pattern shown in the picture. The doors come to the bottom of the floor joist. Unlike the picture my shed has a dirt ramp up to the bottom of the skids the shed is built on, and I use 2x8 boards ramp to drive the tractor into the shed. The minimum clearance under the shed is about 8" and is open on all four sides.

That area between the door and the joist has started to come a part Red area in picture. Since at this time the decomposition is minor. can i stave off the replacement of the door by gluing the loose particles and painting that are of the door?

Is there a better solution?