Pattern paper in Kallax

Is your unit fastened to the wall? If not, you might have a problem if you don't have the weight evenly distributed. I have a 5 x 5 cubed unit and it's fastened to the wall, so I don't have any wiggling when I move any of my bins/cubes in or out.

Ours are Expedits, which look very similar but were built with some different materials, so take what I say with a grain of salt.

I had a 5x5 Expedit with sheet glass and supplies in almost all of the cubes, and that’s heavy - no problem. I didn’t even pay attention to what was put where. We have record albums in a 2x4 on casters horizontally and of course they’re heavy.

I’d put some heavy items in the bottom and maybe forgo casters, though you didn’t mention any. I can’t imagine the middle would be a problem but something should be on the bottom - even if you don’t use it. Reams of paper, for example. If you don’t need anything in that bottom row there are cheap reams of paper on Amazon for just a few bucks.

I just put up a 4x4 kallax unit in my basement. It didn't come with any brackets (I bought it used). It's heavy enough with the paper. I have the paper in the 1st, 2nd, and 3rd rows. It's weighted down. Plus the kallax is heavy enough on its own. I haven't noticed any wobbling or anything in the short while that I've had it up.

If your unit is wider than it is high, the risk should not be as bad. I wouldn't recommend standing it on end and then putting the heavy stuff in the top cubes, and nothing below it, but if you put at least a bit of weight in the bottom it should be okay with your paper further up.

Can you store albums down there? Or heavier accessories in a bucket with a handle that can be lifted up if you need them?

Just put a basket of punches in the bottom row- those things weigh a ton!

I have a 5x5 Kallax that I use as a room divider so not attached to anything, and I have to say that most of the shelves are completely full. I started with my paper in the bottom two shelves, but like you found that it wasn’t the easiest to access. The only paper now stored in the bottom are 12x12 pads with the title written on the spine so that I can easily find what I’m looking for. All the rest have been moved to middle shelves which is much more usable. They’ve been like that for five years now and are showing no signs of bowing. 

Another owner of a 5x5 Kallax weighing in. I have all my paper in the second row up from the bottom. The paper collection fills all 5 cubbies across. It is not attached to the wall, and I've had no problems. The unit even survived being moved by some very careless movers from Florida to North Carolina and it still stands straight with no issues. (I had no plans to move it with me, I was going to buy a new one. Then came Covid - all my scrap furniture moved with me!) Now that I'm looking at it I do notice that kitbot has a good point - my shelves going across are the solid pieces that run from one side to the other. That probably does help with the stability.

I have several Kallax and Expedit units In various sizes. Over the years (at least 10) they have been reconfigured so many directions never paying attention to how the shelves have gone. I have also had them in 3 different homes so they’ve been moved a couple of times. They are loaded with papers and supplies, and haven’t had any problems. I used to have my larger 4x4 unit on top of the large Hemnes dresser. I did have the papers on the bottom of that stack.

They can hold a lot.

(I do not have small kids, so that worry isn’t there for me)

This is what I use in my Expedit I can fit two side by side in each of the cubes and I find them easy to grab/sturdy enough when full of paper. The big draw for me is that they are very easy to flip through.