Bookshelves may begin to bow when you place more items on them than they are made to support. This can happen from purposeful overloading as well as weak materials used to make the shelves. Whether you have stand alone bookshelves or a bookcase with several shelves, you may fix the sagging shelves on your own. You may opt for a quick fix or a more permanent one, depending on your needs and your budget.
Add Support to Stand Alone Bookshelves
Use a tape measure to determine the width of the shelves.
Visit a local hardware store and buy metal brackets for the shelves. Check the size of the brackets to ensure they will not protrude beyond the edges of the shelves. Select screws shorter in length than the thickness of the shelves.
Take everything off the shelves.
Attach a metal bracket directly in the center of the sagging area for each shelf. Usually the bracket will come with its own screws and you just need a screwdriver or drill.
Shelves in a Bookcase — Quick Fix
Take everything off the bowing shelves.
Remove the shelves from the bookcase. They may be screwed in, nailed in, glued in or laying on top of pegs. Tools needed to remove the shelves depend on how they are connected.
Flip over the shelves and put them back in the bookcase. This places the bow so that it now bows up.
Put everything back on the shelves. This is a quick fix that will use the weight of the items on the shelves to straighten the shelves.
Shelves in a Bookcase — Permanent Fix
Use a tape measure to get the distance between each shelf and the width of each shelf.
Cut pieces of 3/4-inch plywood to fit between the shelves.
Paint or stain the plywood pieces to match the bookshelves.
Insert the pieces on each shelf directly under the sagging area. You may need to nail or glue them into place.