ᐅ Kallax shelves tend to sag, especially when loaded with books.

Hello everyone,

A few months ago, I bought a Kallax shelf unit from Ikea, mainly to store books. Unfortunately, I noticed that the shelves—especially the horizontal surfaces holding the books—start to sag significantly over time. According to the product description, the shelves are supposed to have a high load capacity, but in my case, they don’t seem to hold up in the long run. Has anyone experienced something similar or knows how to prevent this?

I’m particularly interested in whether there are reinforcing methods to better support the material or if alternative shelves or additional support braces might be useful.

Thanks in advance for your insights and suggestions.

Hello Lanicholas,

Sagging shelves are a known issue with Kallax units when subjected to heavy loads, especially if many heavy books are stored. The shelves are made of medium-density fiberboard (MDF), which, despite having some load capacity, does not have the solid wood quality that would prevent sagging.

What might help:

1. Add additional supports in the middle. For example, you can screw wooden strips as central braces underneath the shelves.

2. Alternatively, Ikea offers inserts or reinforced shelves that are somewhat more stable.

3. Distribute the load: place heavier books on the lower shelves and arrange them evenly.

4. If possible, avoid overloading the shelves vertically, or install extra movable dividers.

I hope this helps! If you like, I can also find links to suitable reinforcements for you. 🙂

Grace schrieb:
The shelves are made of wood fiberboard (MDF), which, despite having some load-bearing capacity, does not have the quality of solid wood, making it prone to bending.

I can only agree with that. MDF boards tend to deform elastically under load, especially when the shelf span is large.

To solve the problem: an additional central support bar or suitable angle brackets usually provide the best result. It is important to place the support where the shelves show the greatest deflection, often in the middle.

There are also well-made alternative shelves made of solid wood or plywood, which are less likely to bend. Although these options are somewhat more expensive, they can be worthwhile in the long run if the load is consistently high.

Basically, the issue of sagging Kallax shelves when storing books arises from several factors.

First of all, the shelf bracket configuration for IKEA Kallax is standardized: the shelves are typically made of 1.5 cm (0.6 inch) thick MDF panels with a melamine resin coating, which looks good and is durable but has limited load-bearing capacity and flexural stiffness.

The deflection can be estimated using simple elasticity calculations for the structural element: the larger the span (i.e., the width between the side supports) and the heavier the load, the more pronounced the bending will be.

A practical solution I often recommend is to use center supports made of wood or metal that support the shelf approximately at mid-span, effectively halving the span length.

In addition, I advise distributing the load as evenly as possible. If heavy books are placed only in the middle, this naturally accelerates the sagging process.

Specifically, I would like to know: how wide is your shelf? How many books do you plan to place on one level on average? This information helps provide a more accurate recommendation regarding the necessary reinforcement.

kulau schrieb:
How wide is your shelf? How many books do you usually place on one level?

Thank you for the detailed response!

My Kallax shelf measures 77 cm wide (standard Kallax with 4 compartments side by side), and I typically have around 25 to 30 medium-sized books per shelf. This adds up to a considerable load, which I estimate to be about 20 kilograms per shelf board.

I distribute the books evenly, but obviously, I cannot reduce the weight. That’s why I’m wondering whether, for example, a purchased center support beam or additional underlay is truly the best solution, or if there are other recommendations for reinforcing the shelf.

How much effort would that require in practice, and how complicated is the measuring and cutting if I were to make a custom solution?

I can fully understand your problem. I have the same shelf and initially had exactly the same concern about the sagging shelves under my books. It’s really annoying because you almost feel guilty for putting too much weight on the shelf.

Lanicholas schrieb:
whether, for example, a purchased center support or additional reinforcement would really be the best solution

For me, a combination of a simple center support and some lateral bracing worked well because it gave the shelf better stability and reduced shelf flexing.

The effort was manageable: I bought basic sturdy wooden strips, cut them to size, and screwed them under the shelves – it took less than an hour. So, not a big challenge.

As motivation: I was actually surprised by how much more stable the shelf felt afterwards. 🙂