ᐅ Kallax placed on aerated concrete blocks – cracks in the cabinet?

Hello everyone,

I have a question that has been bothering me lately: I placed an IKEA Kallax shelf unit on a Ytong block. The Ytong slab serves as a base to raise the cabinet and provide some insulation. However, I have now noticed small cracks in the cabinet, especially at the joints of the side panels and also slight vertical cracks on the front.

My question is whether placing the Kallax directly on Ytong is generally problematic? Could these cracks be caused by the properties of Ytong as a building material (e.g., uneven load distribution, material deformation, or moisture absorption)? Or is it more related to the construction of the shelf unit or the load applied?

I would appreciate any experiences or technical insights, as I don’t want to damage the shelf unnecessarily but also don’t want to change the base without reason.

Thank you in advance!

Tilis52 schrieb:
Is it generally problematic to place the Kallax directly on Ytong?

Hello,

first of all: Placing furniture on Ytong is generally possible, but there are some important points to consider. Ytong is porous and absorbs moisture, which can lead to swelling or uneven load distribution.

Tilis52 schrieb:
Could these cracks be caused by the properties of Ytong as a building material?

That is quite possible. Ytong can have some unevenness that results in the furniture being more heavily loaded at specific points than others. This can manifest as stress cracks in the wood-based composite frame, especially with furniture like Kallax, which has relatively thin panels.

My advice:

1. Check that the surface of the Ytong is completely level and clean.
2. Place a thin, stable insulating or rubber mat between the Ytong and the furniture to minimize pressure points and compensate for minor irregularities.
3. Make sure the shelving unit is not overloaded or unevenly loaded internally, as this increases stress on the joint areas.

In conclusion: If the Ytong base is uneven or excessively damp, it can indeed cause cracks in the furniture frame. It helps to ensure the base is as uniform and dry as possible.

Hope this helps! 🙂

SauDietmar schrieb:
Ytong can have certain unevenness that causes the shelf to be loaded more at some points than at others.

I would like to add the following: Has anyone checked the moisture levels of the Ytong? It is often overlooked that porous building materials like Ytong can absorb moisture from the air or ground, which over time can cause damage to the surface or interior of furniture.

Tilis52 schrieb:
Especially at the joints of the side panels and also slight vertical cracks on the front side

Cracks in these areas could also indicate inadequate gluing or poor workmanship of the cabinet. Therefore, I would suggest a two-pronged approach: check the substrate (uneven, damp) and inspect the furniture for potential structural defects.

Is the Kallax subject to heavy loads? For example, are heavy items placed unevenly on one side? Tensions can otherwise develop, especially around the vertical supports.

Maybe a foam pad underneath is not ideal, as too soft cushioning can cause deformation. A firm and even support board would be better.

What exactly is placed on the Ytong base? And how is the Ytong protected from moisture coming from below?

Tilis52 schrieb:
I placed an IKEA Kallax shelf on a Ytong block and have now noticed cracks in the cabinet.

Hello Tilis52,

I understand your concern; noticing such damage is naturally frustrating.

Basically, Ytong is a lightweight, very porous material that generally does not provide perfect sound insulation or flatness. It is not prohibited to place furniture directly on it, but it is not ideal. Especially with relatively thin panels like those of the Kallax shelf, uneven pressure points can cause issues.

If the cracks mainly appear at the joints, it is quite possible that mechanical stresses from the uneven substrate are transferring to the structure.

My advice:
- Use a suitable intermediate layer, for example, a rigid sheet of thin plywood or MDF, to level the base.
- The surface of the Ytong should be dry, as moisture could further damage the panels.
- Check the load on the shelf to ensure the weight is distributed as evenly as possible.

In my experience, it also helps to place furniture, no matter how light, on stable wooden battens or risers. This optimizes pressure distribution and prevents moisture from below.

If possible, carefully test whether slight movement makes the cracks worse – this would indicate substrate deformation.

I hope this helps! Feel free to provide more details if you like.