The damage is now so serious that the Duke Humfrey's reading room, which was built in 1422, is to close on Saturday for nearly a year while repairs are carried out.
The Dons who use this room, which stores the university's collection of ancient manuscripts dating back to the 14th century, will be forced to study elsewhere until next July.
For many the transfer to a modern reading room equipped with computers and all the latest technology will come as a shock. The only equipment allowed in Duke Humfrey's is a pencil.
Mary Clapinson, keeper of western manuscripts, said the work was part of a pounds 3m three year restoration of the library.
"All the oak panelling will have to come down and be renovated and then we will be installing a new copper ceiling and installing insulation to prevent the damp which has caused the problem," she said.
"It will also help to regulate the extremes of hot and cold which can damage the books.
"We have been trying to get people organised with their research and to do their work before it closes, but obviously some of them will have to use the other rooms."
Nick Sweeney, a post graduate at the university who uses Duke Humfrey's, said it would be a logistical nightmare for dons and students trying to find the right books.
"People will be restricted in their studies because many of the books have to be kept in special conditions to protect them and that will mean problems getting access to them while the room is closed."Reuse content