ᐅ The back panel of my Kallax unit is developing mold – any solutions?

Hello everyone,

I have an issue with my Ikea Kallax shelf: the back panel appears to be developing mold in some areas, especially in the lower corners. The shelf is in the living room, close to an exterior wall, and is used normally, so there is no excessive moisture.

I understand that Kallax back panels are just thin MDF boards, which are not necessarily moisture-resistant, but I haven’t had this problem before, and I haven’t owned the shelf for long.

Can anyone explain why the back panel is molding? Is it due to indoor humidity, poor air circulation, or the material itself? And most importantly: how can I solve this problem permanently without having to dispose of the entire shelf?

Thanks for any advice!

Pogi59 schrieb:
Can anyone explain why the back panel is molding?

The mold problem on your Kallax back panel is most likely caused by a combination of poor ventilation, high relative humidity, and the non-moisture-resistant material of the MDF back panel.

These thin panels absorb moisture when the humidity remains elevated for an extended period, creating a breeding ground for mold spores. The situation is particularly problematic near the exterior wall, where many older buildings have a cold bridge that causes the dew point to be reached on the back side.

The solution would be, first, to keep the indoor humidity consistently below 60%, ensure better air circulation—especially behind the shelving unit—and, if necessary, replace the back panel or apply a mold-resistant barrier.

Mold on a Kallax back panel? Honestly, Ikea doesn’t really design its products for damp rooms. Your issue is likely not caused by humidity alone but rather the construction.

REN40 schrieb:
These thin panels absorb moisture if the humidity stays high for a long time, creating a breeding ground for mold spores.

That is true, but I would suspect that poor air circulation and proximity to an external wall make the difference.

Perhaps it’s time to reconsider the idea of placing furniture like this—originally meant as lightweight room dividers—directly against exterior walls. That’s where moisture tends to build up, and the furniture just makes it visible.

Hello Pogi59,

You provided a very detailed and excellent description, thank you for that! I fully agree with REN40's assessment.

Unfortunately, MDF is not designed for damp environments, and near an exterior wall, condensation can actually occur. To address the problem, you should consider a few measures:

1. Measure the humidity – with a hygrometer, you can check if the indoor air is too humid.
2. If so, regular ventilation or using a dehumidifier can help.
3. Move the shelf slightly away from the wall to allow air circulation.
4. Replace the back panel with a moisture-resistant board, such as HDF or OSB with a primer/sealant.
5. Alternatively, paint the back panel with anti-mold paint to create a protective layer.

I hope this helps you!

Mold on the back wall means humid air and poor ventilation. Move the shelf a few centimeters (inches) away from the wall; that is usually enough.

If that doesn’t help, use absorbers or a dehumidifier.

Muso4 schrieb:
maybe it’s time to reconsider the idea of placing such furniture (which are actually meant as lightweight room dividers) against exterior walls

That’s an important point. Especially IKEA shelves are often not designed for high humidity exposure, and placing them directly against a cold exterior wall encourages mold growth.

I would recommend improving the indoor climate first. This means ventilating the room by fully opening the windows at least two to three times a day and making sure not to dry laundry in the same room. Additionally, it can be helpful to install a hygrometer to better monitor the humidity levels.

If the shelf is pulled away from the wall, it can dry out, which should reduce mold formation. If the shelf is already damaged by moisture, replacing or sealing the back panel can help limit the damage.