For those folks asking about shelves, I managed to find the online version of step-by-step guide to making floating shelves from hollow-core folding doors. It’s a simple process, and the results are stunning, but warning: this may not be the best option if you’re renting. Even if you alter Step #7 from “glue and then nail along the back” to “use coarse-thread wood screws every 6-inches along the back”, the strength may be somewhat compromised… and it will definitely require a bit of effort to remove (but at least you won’t have to use the circular saw to cut it right off the wall).
Assuming the cleat doesn’t leave a slight impression from compressing the drywall, it’ll still be a good 5/8″ hole left in every stud where you had to drill for the lag-bolts. (If, however, you’re not afraid of spackling, it’s not a size that requires major surgery to cover; it’s just that the holes will, until spackled and sanded, be somewhat, uh, impressive. Comparatively.)
Torsion boxes are incredibly strong — much, much stronger than you’d think, when you look at the separate parts. In this case, hollow core doors are made from two layers of 1/8″ plywood, a lotta cardboard, and 1¼”x¾” solid wood for stiles/rails. What gives a torsion box its real strength isn’t the separate parts but, in fact, the glue between the sandwiching skin-layers. Cheaper (or smaller-width) hollow-core doors will have cardboard in a wiggly-pattern from one side to the other. For a full-size hollow-core door, the cardboard’s more often in a honeycomb pattern.
The more honeycombing going on between the two outer skins, the stronger the torsion box. Thing is, I can’t find anything — even among ‘to the trade’ articles or knowledge bases — that gives an idea of how strong a torsion box really is, in the sense of “use this size, this length, this width, to cover this expanse.” There are adequate estimates, many of which are based on personal experience, but nothing nearly as specific as the charts that designate how much expanse you can cover with hardwood versus plywood versus MDF, etc. This is mostly because the combinations for torsion boxes — material for skin, amount of internal honeycombing (and material used for honeycombing), material for rails/stiles — are so varied that it’d be almost impossible to nail down a specific value outside a random guess.
Instead, I’ll just stick to demonstration. This, from Ron Hazelton’s instructions on building a torsion-box floating shelf: yes, that’s two grown men (and not small grown men, either) sitting on a torsion box. This is the other half of the reason no one bothers to list spans for torsion boxes, from what I gather: it’s pretty much irrelevant. Whatever it is, the torsion box is going to be a lot stronger than you realize, if you gave it plenty of internal ribs. (The link that opens this post says the floating-shelf limit is about 100lbs or so: a test shelf held a set of encyclopedia without a problem. Most likely, the limit there isn’t from the shelf, but how much a single cleat can take before coming right out of the studs.)
In fact, if you want to build shelves on the cheap but can’t afford hardwood that’s anything above the knottiest pine, the cheaper — and in fact somewhat stronger — method is a type of semi-torsion box, itself. Use ¾” plywood for the shelves, but put a facing or ‘lip’ along the front that’s solid wood. This doesn’t have to be a ‘hardwood’ (like oak); softwoods work just as well. IME, Home Depot’s 1×2s tend to be a better cut & less warpage than Lowe’s, but this may be dependent on the local mills. A 1×2 is a construction-grade cut, so it’ll always be cheaper than fancy edging, but if you want to go for fancy and stain/seal the edging, using moulding ½x¾ will give a nice finishing edge (though obviously not quite as strong as what you’d get from 1×2’s larger amt of wood).
For those unfamiliar with why shelves are better built like this (compared to solid-wood-only or plywood-only), it’s not that one-material-only shelf is necessarily bad. It’s just that plywood and solid-wood each have particular strengths and weaknesses, and combining the two uses the best of each while combating the worst of each. Because plywood has a variety of layers in it — 5 to 7, on average — and each layer’s grain runs in a different direction, plywood has a lot of stamina when it comes to fighting off wood’s tendency to curl and warp. This anti-curl strength means plywood has massive amounts of goodness for vertical strength (like when building the vertical supports for a stand-alone bookcase), but its lateral strength isn’t as good as solid wood.
So why not use solid wood for shelves? Well, you could… but you’re also going to pay through the nose for solid wood that’s not knotty and isn’t warped, cupped, or twisted in some way. Plus, just because the wood you purchase today looks straight, this doesn’t mean it’s going to remain exactly like that through its use-life. You get it home, and once it adjusts to your house’s relative humidity, what was a minimal twist may suddenly become way apparent… and now you have a shelf that may be level along the back, but the front edge goes from too high to too low — a lovely twist, and too common, thanks to a combination of inadequate drying time at the mill plus changes in humidity between mill, truck, lumberyard, and your house. Plywood won’t do that; it may curve slightly if you don’t store it flat, but it will also easily slip back into perfectly level once you set it in place on strong supports.
Which means the combination of plywood shelves + wood facing doesn’t just cover the stripey-end of a plywood sheet; it also uses the wood’s grain to keep the plywood from sagging, and at the same time uses the plywood’s strength to keep the wood strip from twisting or warping. (Plus, even if the wood facing is warped slightly, strong glue and judicious clamping can torque the wood back into alignment, by forcing it to follow the plywood’s edge.)
Facing plywood or MDF with solid wood is also a save-move if you have sagging shelves on a store-bought bookshelf. Many of these shelves, from Walmart up to Ikea and beyond, aren’t even plywood; they’re particle board. For lengths of up to about 20″ or so, particle board can hold its own; you don’t really need the expense of solid wood if you’re talking about such relatively short spans. The problem is that over time, if you’re storing huge weights on the shelves — and I suspect the majority of you are a lot like me, with too-many-damn-books — then the particle board will start to sag. In some cases, the bookcase design means you can remove the shelf and flip it over, letting the weight of the books push the curvature down to straighten out the sag. Problem is that eventually this pressure will carry on through until the particle board is again sagging.
In that case, a simple strip of wood glued, nailed, or screwed along the front (best is glue + finish nails) will reinforce the shelf and extend its life. You can either flip the board and weight it until it’s near-to-straight, then attach the edging, or — if it’s a non-flippable shelf — you can lay it on a flat surface like your kitchen or bathroom floor, and stack all the books on top. This will push the particle board down, and then you attach the edging. Don’t remove the weights until the edging-face glue is dry, and the edging’s nailed into place — you don’t want the shelf’s curvature to force the wood to curve as well.
If your bookshelves are faced with a colored veneer (such as white, black, whatever laminate), you can paint the wood or stain/seal and use the edge as accent. Based on experience, prime/paint, or stain/seal, the viewable edges of the wood — not the side to be glued!!! — before attaching. (Otherwise you have to do the whole taping-covering crap with the shelf after the front edge is in place.)
If you want to paint the entire unit, there’s a nifty spraypaint now available that’s designed to be used as primer on plastic and plastic-like surfaces. Prime lightly with that, paint whatever color you want with a regular latex-based paint, and then seal with a water-based poly. Two coats of the poly and you’ll have a non-yellowing seal that will stand up to a lot of abuse.
An equally witty concept, over on instructables, is for creating floating shoe shelves out of PVC pipes. Easy, lightweight, and damn cheap! Best part is that if you live in a rainy, snowy, or muddy place, raising your shoes like this means water and mud can drip onto a moppable surface. (Or you can use the method an equestrienne friend used, which was to keep a low, cheap, plastic container under the shoes to collect dripping mud and/or melting snow, which could then be emptied without the carpet getting messed.)
Last, on wall shelves: these ‘Hungarian Shelves’ may be easier than dealing with floating shelves (unless you, like me, have a handful or more of ugly folding closet-doors that will hit the trash unless you can come up with some use). The concept for these wall shelves is pretty much identical to the design in Ikea’s Varde shelves, and I can attest to the strength of those puppies.
FYI, FWIW: in this case, the shelves are solid wood. Unless you really want to deal with the process for creating a strong solid-wood shelf that won’t have the usual sag/bed/curl/warp issues, I’d recommend the plywood+edging route. For those of you who look at the Ikea shelving (or similar) and say, “it’s not solid wood, it’s just strips!”, the instructional moment here is that gluing wood strips under pressure is using the grain-layering method of plywood, but with solid wood.
If you prefer solid wood but either ended up with pieces that are good looking but cupped, or alternately, you don’t want to risk cupping as the wood settles into place… then laminating (that is, gluing) thinner strips together creates a non-warping, much-stronger, plank.
First, gluing long-grain to long-grain is the strongest glued-joint you can possibly get (which is what you’re doing here, between the strips). In fact, the glued joint in some cases may be stronger than the wood around it — which means the lateral strength of wood treated in this manner is phenomenally strong.
Doing shelves like this doesn’t mean the manufacturer was “too damn cheap” to use a solid piece of wood, because when it comes to the strength you need for long-enduring (and major-weight carrying) shelves, this method is among the best. It’s just a side benefit, really, that it’s also much kinder to the environment in a production facility, because the wood used can be a variety of odds and ends rather than the tree-intensive cutting to get 12″ wide boards.
Which is to say: the next time you look at a bookcase, butcher block, tabletop, or any other structurally-important or weight-bearing lateral surface and someone decries the “lots of small pieces” as being a bad thing… you can set them straight. Mocking them behind their backs is also acceptable, if you prefer.
Tagged: carpentry, construction, shelves, storage