Looking for load-bearing plastic blocks (cheap)

I’m thinking of using some wooden planks that I already have to build some bookshelves. Remember in college when you’d use concrete blocks and boards to build shelves? That’s what I want to do, but I don’t want to use heavy concrete blocks or bricks (which I don’t have, anyway). I looked around for something plastic. I found these planter corner wall blocks but they are not load-bearing. I found these construction blocks but they’re super-expensive and overkill for what I want to do. Does anyone have a suggestion for something cheap, load-bearing, and not super-heavy that I can use for this purpose?

Plastic milk crates?

That is what my wife was using in her apartment when we started dating. 4 milk crates and 2 strong boards for her stereo and albums and some other misc. stuff.

Milk crates are remarkably strong and lightweight. As your local grocery store or restaurant. They might have some you can “borrow”.

Do they have to be plastic or do you just want them to look like plastic?
If it’s just the look you’re after, you could find something else suitable and put a few coats of Plasti-Dip on it. That’ll give it that shiny (or matte, if you want) uniform color and texture that should replicate plastic.

You might also take a look at valve boxes for underground sprinkler systems. Most big box hardware stores will sell them in a variety of sizes.

Rolled up corrugated cardboard would probably be strong enough.

I was gonna say even the cheap type decorative milk crates that weren’t made to carry milk should be strong enough for making shelves. They are incredibly strong under compression, but you may not be able to leave the open top part facing out for storage if they are not all that strong. The trouble with that theory is that nothing is cheap anymore, here’s a pair of milk crates for $25 bucks on Amazon. They look to pretty sturdily made though.

You might find some simple plastic storage containers for less than that on sale, but the price of everything is horrific.

This isn’t exactly what you’re describing, but I thought you might want to consider them:

For the most part, the stores or even the corporate chain does not own the milk crates, they’re the property of the dairy vendor, and they expect to get them back.

True in some cases, but my wife manages a restaurant and the dairy provider never collect the crates. You can have as many as you want.

I’ve purchased used milk crates from a dairy/distributor. I bought a dozen used crates for a dollar apiece. They are great for storage, boat stuff, making shelving units, etc.

What about non-heavy concrete blocks? You can get aerated concrete blocks that are so light they float in water - like these: Toplite Aerated concrete Block (L)440mm (W)100mm (H)215mm | DIY at B&Q
-not that you would want to put them in water - they are also porous. They can be cuit to size with an ordinary hardpoint hand saw, and for indoor use, you could paint them with wall paint.

About 20 years ago I built my daughter a shelving unit using 1½" PVC pipe. I made two 5 foot tall ladders for the uprights and two 4 foot ladders for the top and bottom using straight pipe and T connectors. These are connected to each other with elbows. I originally used particle board for the shelves but they sagged over time so she had someone make her new shelves from 3/4" plywood. She is still using it today.

Thanks for all the ideas, keep them coming! It’s starting to look like milk crates for me. I am finding places online that are a lot cheaper than the Amazon link above. And I will keep looking for used crates somewhere. I’m still open to any other ideas that would work.

My water bed has sat on 11 or 12 plastic milk crates for over 40 years(jeez, I am that old). No issues with them at all.

The dollar stores sell fake milk crates for like a dollar.

They do, but generally they’re a lot weaker than actual milk crates.

Not plastic but glass window blocks come in several sizes and designs, they aren’t expensive:

Another route would be the same type of block from a craft store such as Hobby Lobby, Michael’s or Joanns. They sold with an opening in one side so decorations could be inserted (or fairy lights.

I think glass blocks are a great idea for making shelves. It probably requires are at least 2 on end for each support, but still not that expensive and available in different colors. Also easily reusable for other purposes or to build a glass box wall or window.

Wire cubes are cheap. Don’t use the plastic corners. Instead zip tie them together and put one or two sides inside vertically for extra support. If that’s not strong enough, zip tie another side to the front.