Shelf for attic - sloping roof without knee wall

That's right! So far, I have only found the parts in "2x large base" + "2x narrow base". Do you happen to know a model that can be built as "1x large base" + "1x narrow base"? That could be a good solution.

I have the ones from Obi, they have 5 identical bases, and if you need a very wide base, you just put two of them in a row ;)

Yes, a lot of space is lost. Behind that, we have things like spare tiles, a crib, a changing attachment. Things you rarely need to access. On the shelves, boxes with things you need to access more often.

[Ivar] is by the way quite expensive if you want to achieve the same storage capacity as with a heavy-duty shelf.

I still had some Ivar parts left over from my previous apartment, which I installed under the roof. I think I even shortened them by a few centimeters at the back to get the shelves further under the roof. With low slopes, every centimeter counts. In the garage, I have the heavy-duty shelves from toom. They are good, but 1. the setups for the boards are very high. That wastes quite a bit of space. Also, to my knowledge, you cannot purchase additional tiers.

Not at the hardware store, but maybe from the manufacturer? Otherwise, you just buy complete shelves. One costs as much as two shelf boards for IVAR (not even on sale). The assembly part is true though. You always lose about 3cm there.

I don't have a solution for our attic yet either. I would also prefer to use every cm, but I don't get around to building it myself (there are many instructions for that). At the moment, there is a very low shelf placed as deep as possible in the slope, but there isn't much space inside...

And the solutions: "Something tall in front and using the space behind for things you don't need often" I find super annoying because when you do need it, it's really inconvenient to get to it.

Maybe Kallax cubes in three heights on wheels are a quick solution? (found on Pinterest)