|We’ve built stable shelving units as tall as about 10 feet. Stability requires the proper foundation. You’ll do best if your lowest layer has all the crates oriented in the same direction — either horizontally or vertically — and can be braced against the corner of a room. The second layer of crates should overlap the first — i.e., you should start a few inches in from the edge of layer #1, so that each crate spans two of the crates below it. [As you place your crates (and as you fill them), you should try to really jam each new crate against its neighbors.] On layer #2, you can begin to mix vertical and horizontal boxes. Depending on how you do this, layer #3 will begin to introduce “gaps” into your structure — interesting negative spaces, also useful for storage. [Sometimes, you’ll want to plan these gaps in order to retain access to electrical outlets or heating ducts; the flexibility to do so is a real advantage of Home Organization Tools.] If you’re planning on building a very tall structure and want the utmost in stability, a few well-placed C-clamps do the trick. A home organizer in Manhattan can make other suggestions.
Another factor to consider is the slope of your floor. In many older houses, the floor tends to be highest along the walls, sloping downward toward the center of the room. In any case, what you want to achieve in your shelving units is a backward slant — you want the front edges of the crates to be slightly higher than the back edges. If the crates have this slight tilt, gravity provides extra stability for your structure — your shelves will be wanting to topple away from you, towards the wall, where they can’t go anywhere. So, as you’re adding layers, starting from the first, use a level to check your tilt and add your choice of shims to keep a constant backward slant. (If you don’t have a level, you can test the direction of tilt by placing a marble on top of the crate and watching which way it rolls.)
We’ve also built free-standing units from these crates — room dividers, about 5 feet tall. Stability was achieved by arranging two sets of crates, back to back. Store your heaviest stuff in layer #1.