ᐅ Are movement joints necessary under Kallax units when installing parquet flooring?

Hello everyone,

I couldn’t find clear information about movement joints under Kallax shelves on parquet flooring and would appreciate your expert opinion on this topic. My specific question is: Are movement joints necessary under Kallax units when placed on parquet floors?

I understand that parquet flooring generally requires movement gaps around the edges to accommodate expansion and contraction caused by temperature and humidity changes. However, the shelf stands directly on the floor and might either “seal” that gap due to the pressure or, conversely, restrict the floor’s natural movement because of its weight.

Are there any recommendations on whether to leave a separate movement joint under the Kallax, or is it okay to place the shelf directly on the parquet without causing issues? How does the floor’s lengthwise expansion behave under the shelf?

I look forward to your assessments and experiences!

Interesting question, Birgittv52!

I have a somewhat different view on movement joints under Kallax shelves: In my opinion, these joints under shelving units are almost unnecessary because the furniture itself does not absorb moisture and does not significantly affect the expansion and contraction of the flooring. Of course, the floor needs an expansion gap around the edges, but whether or not there is a shelf on top does not change that.

Birgittv52 schrieb:
What about the lengthwise expansion of the floor under the shelf?

That is exactly the point: The expansion occurs across the floor surface, not necessarily directly under the shelf. The floor can also move beneath the furniture if the bonding is strong enough. Additionally, I think a joint under a shelf is more of an aesthetic choice than a functional one.

Therefore, I suggest focusing on ensuring that the perimeter expansion gaps are sufficient and that an extra joint under every piece of furniture is not necessarily required.

Hello Birgittv52,

I would like to address your question from a more technical perspective, focusing particularly on the process and material properties.

Engineered wood flooring, especially multilayer parquet and finger-jointed plank types, expand differently in length and width depending on the wood species and indoor climate. Expansion gaps are used to accommodate these size changes to prevent warping, cupping, or even lifting ("buckling"). These gaps are usually left open around all fixed boundary surfaces.

Now regarding the Kallax shelf: since it rests on the parquet with its weight, it may locally restrict the floor’s ability to move. This means the floor under the shelf cannot move freely, and the expansion allowance shifts to the surrounding area. If the shelf is very large and the parquet floor does not have adequate perimeter gaps, tensions may develop in the flooring.

SIAURORA schrieb:
The expansion occurs across the surface, not necessarily directly under the shelf.

That is basically true, but the weight on the parquet still reduces the deformation capability exactly at this spot. Also, this issue varies depending on the room size and the installation method used (e.g., floating or fully glued).

My recommendation: If your Kallax covers a larger area (e.g., wider than 1 meter (3.3 feet)) and your parquet is installed as a floating floor, it is better to leave an expansion gap below the furniture or at least check whether the surrounding gap is sufficiently sized. Otherwise, there is a risk of tension damage to the parquet.

For small shelves or heavy furniture that only rest on a small floor area, it is usually not a problem if no additional gap is planned.

How large is your Kallax and how is your parquet installed?

Hello everyone!

This is really an interesting topic – I love it when we can discuss such details! 🙂

A brief note on my experience: I have a Kallax shelving unit standing on a floating hardwood floor. I deliberately made sure not to place the shelf completely flat on the floor, but used small felt pads (only slightly elevated) so the hardwood can still "move" a bit. I didn’t leave a gap under the shelf itself, only paid attention to the perimeter expansion gap around the floor.

FABIAN_DEO schrieb:
If your Kallax covers a larger area (e.g. wider than 1 meter) … it’s better to leave an expansion gap under the furniture

That makes sense to me; I have several smaller Kallax units next to each other, so the overall footprint is quite large. After setting it up like this, I noticed that the hardwood floor doesn’t buckle or build up tension anywhere.

So my conclusion is: expansion gaps underneath Kallax units are not absolutely necessary, as long as the hardwood floor has enough space to expand around the edges.

It’s amazing how such small measures can have a big effect! 🙂

Keep up the great exchange of ideas!