ᐅ Have any of your Kallax doors warped after painting?

Hello everyone, I recently painted some doors of my Kallax units to give them a new look. Now I've noticed that some doors warped after painting, so they no longer close properly or get stuck. My question to you: Have you had similar experiences with Kallax doors warping after painting? If so, what do you think causes it exactly? Do you use specific types of paint or preparation methods to prevent warping? I would like to understand how to avoid this problem, as I do use primer, sanding between coats, and apply thin layers of paint, but apparently, that is not always enough. Thanks in advance for your feedback!

Hello fu-bla, I am very familiar with the issue of warping in Kallax doors after painting and can explain quite a bit about it. Basically, the material is usually coated MDF or similar engineered wood products, which are quite sensitive to moisture and heat. During painting, the surface is moistened, and depending on the type of paint, tension builds up during drying. Often, the wood fibers or MDF material contract unevenly, causing the door to warp along its length or width.

Thick layers of paint or sensitive water-based paints are especially problematic, as they first cause swelling and then shrink slowly. The primer also plays a significant role, especially if it is not applied evenly or is too wet.

If you have doors painted on both sides but not with the same layer thickness, this can also lead to a kind of "bimetal effect" causing the warping. Have you treated all sides of the doors equally or only the visible ones? Also, what were the ambient temperature and humidity during painting and drying? These factors can also affect MDF.

In short, to avoid warping, it is best to apply paint very thinly and evenly, ideally treating all surfaces on both sides, and to ensure drying times occur in dry, temperature-controlled rooms. Have you followed these steps?

danial60 schrieb:
If you have doors that are painted on both sides but with different layer thicknesses, this can cause a kind of "bimetal effect" that leads to warping.

Yes, that could definitely be the key point. In fact, I usually left the inner sides of the doors unpainted or only treated them with a very thin layer of clear coat, while the front side received more layers. That could well cause uneven stresses.

danial60 schrieb:
What were the ambient temperature and humidity during painting and drying?

For me, it was winter in an unheated garage, the air was quite dry, around 30-40% humidity, temperature about 8-12 degrees Celsius (46-54 °F). I always allowed relatively long drying times, usually several days between coats.

Thanks for the detailed explanation so far; I will consider properly treating the backs next time. Is there anything else I should keep in mind?

Paint both sides, applying thin layers. Make sure to keep the same layer thickness on the front and back to prevent the doors from warping.

The issue is well known: MDF doors absorb moisture and therefore react to uneven treatment. Paint seals the surface but cannot completely prevent the material from moving.

In addition to painting both sides, I recommend using a high-quality primer before applying the paint to seal the surface. This should minimize moisture absorption. It is also important to store the doors flat during drying to prevent warping in one direction.

I also advise applying the paint in as thin layers as possible and allowing each layer to dry fully before applying the next. Too thick layers cause stresses that can lead to warping.

Hey, I also painted my Kallax doors and was able to minimize warping by sanding them lightly on both sides, then priming with a bonding primer, and finally applying three thin coats of paint. Always lay the doors flat to dry instead of hanging them up!

This really helps because the doors don’t bend, and moisture can escape evenly. It’s really satisfying when it works! 🙂