I'm with
@francist on this one—vertical is the way to go. But your needs will vary depending on if you lean towards machining vs. fabrication. My original one was horizontal, and if you look closely on the pics you can see how it was designed that way, but later converted to vertical. Vertical takes up less space and is easier to access material from. But originally I thought, "how am I going to stand up 10' material in a 9' shop, so I built horizontal. Turns out that all the long stuff I buy I cut up almost immediately, and the shorter off-cuts can be stored in the vertical rack now, or organized like
@Dabbler says. (You can't store short off-cuts vertically as easily if you think about it—unless you have shelves that are solid or expanded.)
Put it on casters, and use a chain or something to restrain stock, but such that it can be removed to get the longer stock out easily. Design some kind of a bracket system to isolate types of material—this is critical. Mine are rigid; but I wish I had made them adjustable. The best system I ever saw was at Metal Supermarkets; they use brackets that just slide on horizontal cross members to hold material but can adapt to your needs. I wish I had done that.
I do have
some horizontal storage in a garden shed where I hang chain from the rafters. It's perfect for longer 10 and 12 foot lengths when I spot a good deal on tubing or angle iron I can't pass by. But once they are cut under 10'—they go into the vertical rack inside.
Give some thought to secondary storage too. I added a few metal bins I made on the back for scrap and off-cut pieces, and storage for some sheet goods. In the pics you can see the sheet goods at the back of the rack. I never regretted it for a sec. Sheet goods rust even in a shed, so the sooner you can move them inside the better. Don't skimp on the casters BTW; bigger is better. As noted by
@francist, a loaded rack is tough enough to roll as is...you don't need some tiny metal shaving stopping your casters dead in the water if they are too small. While on the topic—think a bit about placement of the rack. If it is in a tight place of your shop, consider swivel casters on all four corners—despite conventional wisdom. In a small shop like mine, for example, being able to move the rack in any direction (thanks to four swivel casters instead of two), is a blessing. Another thing noted by
@francist is the wood bottom. While I try to avoid flammable material in a welding shop as much as possible, the wood floor is something I would do if I were building another rack. That's because i skinned mine with 16 gauge sheet, but it can be slippery—especially for sheet stock at the back. Sheet will always slide when stored on edge. A wood floor prevents this, which is nice and a good compromise it you don't have the space for flat sheet storage like a pro shop.
One last thing. As your collection of scrap and off-cuts grows, it gets harder to control. Stuff falls over and gets lost behind bigger pieces. Next thing you know you're buying material when in fact you already have what you need, but it just fell behind other stuff and now you just wasted money. The secret is to group stuff together and wrap it so it doesn't get lost in the pile. It took me years, but my lesson was to use that stretchy plastic wrap you can buy on a roll from places like Princess Auto. At first I thought it wouldn't be strong enough for metal, but with just a few wraps it is actually strong enough to transport large angle iron on a flatbed. Best of all it is dirt cheap and you just cut it off and replace it when you need a piece. Totally worth it
Best of luck
@cuslog . Post whatever you come up with as a solution...we'd all love to see pics.
