ᐅ What to do if Billy bookcase shelves start to sag?

Hello everyone, I have an issue with my IKEA Billy shelves that many of you might be familiar with: the shelves, especially the larger ones, start to sag noticeably over time when I store books and other heavy items on them.

I’m looking for effective, practical solutions to prevent or at least reduce this sagging without having to replace the entire shelving unit. What options are there for reinforcing the shelves? Are there specific additional support strips, better fasteners, or alternative materials that can be used?

I’m also curious whether this is mainly a question of load or shelf size – what is the maximum weight or dimensions the contents should have to avoid the shelves bending?

Thanks in advance for your tips and experiences!

fivin43 schrieb:
I am looking for effective, practical solutions to prevent or at least reduce sagging

This is a very relevant topic. Fundamentally, when it comes to the Billy bookcase, you need to differentiate between two things: the load-bearing capacity of the shelf material – usually particleboard with a melamine coating – and the span between the side panels.

Sagging is primarily caused by the span. For example, if a shelf is 80cm (31.5 inches) wide and loaded in the center, it will bend more than a board that is only half as wide. In addition, the material itself plays a role: particleboard has limited stiffness and elasticity, which becomes noticeable over time.

A proven method to reduce sagging is to add a central support strip or a second shelf that acts as additional reinforcement. Often, lightweight strips made of wood or metal are installed in the middle, which can be screwed or glued under the shelf.

Note: It is important that the support strip fits snugly against the side panels and is firmly screwed in place – otherwise the weight shifts and the problem remains.

Also, consider distributing the load: avoid placing all the books or heavy items on a single shelf, and spread out the weight.

I would be interested to know how deep and wide your shelves are, and how much weight they currently carry on average. Then I can provide more targeted recommendations.

Shelves can be easily supported in the middle with metal brackets. Alternatively, thicker wooden strips can be attached underneath. Keep the load within limits, ideally not exceeding 15 kg (33 lbs) per shelf.

Laukau5 schrieb:
A proven method to reduce sagging is to install a central support strip or a second shelf that acts as additional reinforcement.

I agree with that. To be more specific: I added sturdy MDF strips less than 2 cm (less than 1 inch) thick directly under the shelves of my Billy bookcases. These strips run centrally from front to back and provide significant rigidity.

It is important that the length of the strips matches the exact depth of the shelf so they don’t protrude sideways. This becomes especially noticeable when holding heavy books.

Additionally, it helps not to overload the shelves completely but to leave some space every 5 to 10 cm (2 to 4 inches) between the books. This way, the load is better distributed.

Another commonly overlooked point is to make sure the Billy bookcase is precisely plumb and aligned against the wall. If it tilts or wobbles, the stress on individual points increases, which worsens sagging.