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I have removed several old and moisture damaged built in storage units from my house. I would like to replace them with shelving. There are a number of different sized gaps (width and depth to fill).

I would like the shelves to hold quite alot of weight (large numbers of books and similar).

Some of the shelves I would like to span quite a width. For example, 2 meters, and be quite deep (say 50cm). For aesthetic reasons I would like them to be supported only at the back and each end, avoiding large brackets or similar underneath the shelves as far as possible.

One way to do it would be to buy very thick strong material for the shelves. I would like if possible to avoid having to spend that kind of money. I would like to use cheaper and lighter materials, which I can apply some kind of finish to (paint or something).

What methods of construction, other than using a single thicker stronger piece of material, can I use to improve the distance a shelf can span before deflecting too much or collapsing? What are the limits (span, depth, load) of these different methods of construction?

(I have already solved the source of the moisture problems)

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13 Answers 13

I'd use plywood with a thicker piece of hardwood glued onto the front edge. This gives you very good strength. Here is an online calculator I use to find what kind of materials you can use and the amount of sag you will have. Here's a good quote from the author of the site.

“The eye will notice a deflection of 1/32″ per running foot.”

The sagulator

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That is a really useful calculator, thanks. –  flamingpenguin Feb 23 '11 at 14:10
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For a more in-depth beam deflection calculator with different loadings and methods of support, try: aps.anl.gov/APS_Engineering_Support_Division/… You may need a little bit of engineering background though. This website is a little more user-friendly, but doesn't have an automatic calculator: engineersedge.com/beam_calc_menu.shtml –  Doresoom Feb 23 '11 at 14:56
    
BTW, moment of inertia (I) can be calculated for a rectangular cross section by I=1/12*w*h^3, where h=height (direction load is applied) and w=width. –  Doresoom Feb 23 '11 at 15:10
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This is a pretty good answer and I agree with the hardwood front stiffener. Add one other component. Put a piece of 1X stock across the back wall between the end supports for the back edge of the shelf to rest on. This will support at least 1/3 the width weight, and the stiffener on the front will help with front edge sagging. Definitely use at least 3/4 inch stock for the shelf. This is a good practical answer to your situation –  shirlock homes Feb 23 '11 at 21:08
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@flamingpenguin: Actually, if the calculator is assuming a simply supported beam (fixed only at endpoints), it won't be applicable for a shelf supported on 3 sides. You're not going to find an easy calculator for that situation - that's FEA territory. –  Doresoom Feb 24 '11 at 14:43

Strong and light and cheap? Take a look at torsion box construction.

enter image description here

Granted it's not exactly thin but as @Joe mentioned, getting all four of those qualities is a tall order.

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This is basically a construct-your-own version of the hollow door possibility mentioned by @Joe. –  Martha Oct 21 '11 at 19:19
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Sure, but building it yourself gives you more control over how well the parts are glued together, what material it's made of, how it's mounted to the wall, etc. The one hollow core door I've cut open used lightweight fiberboard around the edges, cardboard inside for stiffening, and the skin material was ~1/8" thick masonite. –  Mike Powell Nov 29 '11 at 7:09
    
I recently had the misfortune of disposing of some Ikea furniture. It was an approximately 2 meter span shelf supported at each end and designed to fit over a bed. I had to saw it in half, and it turned out to be constructed pretty much like this. The battens were made of veneered particleboard and the faces out of veneered hardboard; but the voids were filled with a cardboard lattice. There was a batten on all 4 sides and one across the short dimension near the centre (no rebate). It was pretty strong and light, although not particularly thin (~7cm). –  flamingpenguin Sep 28 '12 at 9:42

You want strong and cheap and light and thin? You're asking for a lot.

You can get lighter by making a laminated shelf with honeycomb in between ... but it won't be that cheap, or all that thin.

You can get cheap and light by adding a couple of stringers along the bottom as stiffeners, but it won't be all that thin. You could use something other than wood so it's thinner, but then it won't be cheap.

... so that only leaves one alternative that I can think of -- you didn't say that it had to be flat. So make an arch. Yes, it'll be a whole lot of work, but if you got think sheets, and glued and clamped it to laminate it into an arch, it'll transfer the load laterally as it took the weight, so the weight gets transfered better to the ends.

Of course, when you factor in all of the adhesive, it might not be as cheap as just going with a thicker piece of heavy plywood, and it's going to be significantly more work, and be much less practical in the end, but it'd at least get three of your four desired qualities.

As for the span limits ... it depends on the material used, number of layers, final thickness, and the amount of arching.

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Yeah its asking alot :-) I realise that there are always going to be trade off involved. The arch idea is very interesting. It could make an attractive alternative to big metal brackets. But it would prevent lower shelves from using some of the space above them. I guess it might be possible to use two half arches at each end of the span too? –  flamingpenguin Feb 23 '11 at 14:03
    
I wonder if you could describe a bit more the honeycomb that could be used in the laminate idea. What could it be constructed from? –  flamingpenguin Feb 23 '11 at 14:05
    
I've used this stuff before with a carbon fiber layup for an SAE RC aircraft heavy lift competition. aircraftspruce.com/catalog/cmpages/01-00488.php The finished product is unbelievably strong and lightweight. Not very easy on the wallet though, and probably not the best option for shelves, when shelf weight isn't an issue. –  Doresoom Feb 23 '11 at 15:43
    
Arching shelf! That's brilliant! –  Vebjorn Ljosa Feb 23 '11 at 16:04
    
@Doresoom I remember seeing something that looks similar but is made of cardboard (and presumably much cheaper). I wonder if that is vaguely strong enough and could be used or if it would be too easily squashed, might have to try and get some and do some tests. –  flamingpenguin Feb 23 '11 at 16:10

You could try a plywood shelf with a run of EMT or other rigid pipe underneath. Hang the pipe with some closet flanges, and then lay the shelf on top of those.

To cover it up, you could paint the pipe, and cover the front of the shelf with a face frame.

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Interesting idea. How would I go about working out what diameter of pipe is required for a given span/load? –  flamingpenguin Feb 24 '11 at 11:10
    
I am not aware of any load bearing tables for typical conduit pipes. To get some idea, you can go to the hardware store and check out the conduit there. I would start with maybe 3/4" or 1" galvanized (thickwall) pipe. If you can find a spot in the store, try and prop it up at the ends and see if it will deflect under your weight. –  James Van Huis Feb 24 '11 at 21:35

I just had another random thought on this ...

hollow door blanks.

Yes, it's thicker, and you'd have to get them just the right length, as you can't trim 'em down too much, but the construction would make it quite stiff ... it's actually similar to the honeycomb idea ... the honeycomb isn't to give strength, it's to make sure that the top and bottom layer are a distance away from each other so they can take a better moment. (well, and for epoxied applications, it also keeps them from being able to separate or move closer together)

I don't know what the ultimate load-bearing capacity would be, though.

It looks like the Home Depot near me sells various widths of "Wood Unfinished Flush Slab Door", all 80" tall (a hair over 2m) for $21 (18" / ~46cm wide) to $33 (36" wide)

The only thing is ... if you need to strengthen it further, I'm guessing it'd be best to laminate another layer on top (both to stiffen the compressive layer against deflection, and to provide durability if someone drop something heavy on it. ... which is a little more work than adding a stiffener to a piece of plywood.

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I found this page which describes a method for making 9' width floating shelves from hollow door blanks. wikihow.com/Build-Simple-Floating-Shelves –  flamingpenguin Feb 25 '11 at 10:02

Put shelf boards on horizontal rods of steel which are set into drilled holes in the wall, with the rods perpendicular to the length of the shelf. Grooves may be cut in the bottom of the boards to fixate them on the rods. Depending on the thickness of the boards, you may even be able to hide the rods. Yay! Magic Shelf!

This will only work if your wall is strong enough, meaning 20cm or thicker stone or concrete.

The setup works in my dads workshop. Rods are 1m apart, Grooves are shallow, boards are tongue & groove 16mm, 60cm deep. The rods are steel pipes 16mm diameter, not simple iron. The wall is massive concrete, 24cm deep. Holes are prolly 16-20 cm deep. Not sure anymore, we drilled the holes like 30 years ago. The shelf is loaded with tools and materials and holds very well. While the boards are shorter than the length of the shelf, the tongue & groove helps distribute the load at the joints. The shelf runs about 3.5m with 4 rods per board.

I guess a wood wall would just buckle.

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Bamboo is not as straight & controlled as traditional lumber, but its strength is outstanding over large spans.

In the town I used to live (Redmond WA), there was a bamboo farm where they sold bamboo just like lumber at a lumber store. Out of curiosity I used it in place of traditional wood in many projects, and I have to say, I am amazed.

For example in one project, I wanted to build a crane. Materials for the boom had the same problems: too heavy, too thick, too expensive. We tried a bundle of bamboo and found it satisfied all our conditions with flying colors. The drawback is that the visual impact was not pretty. So in that regard, get creative :)

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I guess it would have a distinctive visual effect. What would the construction method be? Rest the bamboo next to each other and on supports at each end and somehow tie them together in a few places? –  flamingpenguin Feb 24 '11 at 11:21
    
The methods I used were, I would say, primitive. Pipe straps, screws, that kind of thing. Being mostly hollow, most traditional woodworking techniques don't work. I can think of a couple general approaches: 1) tying like you say, 2) screwing to the nodes (which are the only "solid" part of the bamboo) 3) finding bamboo in compressed dimensional form, like from here calibamboo.com/bamboo-lumber-lumboo.html. I have never worked with that though and have no idea how it performs. –  tenfour Feb 24 '11 at 11:45

Cheap, super strong, and hidden...that's going to be tough.

Given that equation, you'll have to sacrifice somewhere and I'd suggest investing in a lot of time and labor.

I'd look into taking down all the sheetrock/plaster. Then reinforce the studs with custom metal places that have welded-in-place i-beam brackets. The plates would then be bolted to the studs (and, ideally, the studs reinforced to the base and top plats with simpson brackets)

The brackets would have to be designed and engineered, but likely wouldn't be that much to have a local welding shop do that.

Then, finish the wall and you can then create shelves that completely cover the brackets giving the illusion of floating.

This has the advantage of putting the strength inside the wall, therefore hidden.

This has been done for things like floating staircases where the tread appear to be hanging out from the wall unsupported.

Another thought, which would depend on what's above your ceiling, would be to attach angle iron to the wall to support the back of the shelve, then use some form of cable/wire system hanging from the ceiling to support the front of the shelves. Not quite as 'hidden' but less obtrusive than large brackets.

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My walls are made of concrete blocks and covered in plaster (not stud/drywall), I'm not sure how I can adapt this idea. –  flamingpenguin Mar 2 '11 at 10:59
    
You could bolt wood studs to the wall, attach mounting brackets/plates to the studs, and then sheetrock over studs. –  DA01 Mar 2 '11 at 15:10

I like parts of some of the existing answers. The obvious solution to me seems to be the 3/4 inch plywood, as others have mentioned, with the thin wooden support on the wall all along the length of the shelf. That gives lots of support. In addition to that, assuming it is a painted shelf, I would attach a piece of L-shaped aluminum angle iron all along the front edge, screwed into the bottom of the wood of the shelf with the L-shaped flange sticking down. This gives support for the shelf, and the metal edge sticking down would counteract a huge amount of weight that would otherwise tend to bow the shelf. This might allow you to use a thinner plywood as well, maybe 1/2 or even 1/4 inch, as 3/4 inch plywood is seriously heavy in itself. Just my 2 cents worth, hope this helps.

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Nice idea, what kind of thickness of aluminium and size would be appropriate? Is there a way to calculate it? Would 1/2" x 1/2" x 1/16" be appropriate or would something bigger/thicker be needed? –  flamingpenguin Feb 28 '11 at 10:57
    
I'm sure there is a way to calculate it, though I don't know right off hand what that is. My thought was just to go by intuition, based on how much weight you expected to put on the shelf, and then maybe build one and try it. The 1/2 by 1/2 by 1/16 seems like a good place to start. If you look at it in Lowes, that 1/8 material seems pretty beefy, so you would only need that for carrying a lot of weight. Sorry I can't give you a more exact estimate. –  AWMoore Feb 28 '11 at 22:15

I have used old metal bed rails. They will support a lot of weight, and I have found them for next to nothing at garage sales.

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Many answers recommend plywood. I'd like to point out that the construction of plywood (adjacent plies having their grain at right angles to each other) makes plywood equally strong in all directions whereas what you want is maximum strength in the long direction of the shelf. Strength in the short direction is pretty much wasted.

Thus, solid wood seems more appropriate for shelving than plywood assuming the same species of wood and no significant knot holes.

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The following might be helpful - doesn't address all your needs, and depends on having a wall with 2x4 wooden studs inside rather than your concrete block, but some ideas may apply.

I just finished a project similar to this. In my garage I wanted cheap, strong shelving, 16" deep with a minimum of support structure, for storage of heavily loaded 12 gallon tote boxes.

I cut 20 foot lengths of 1/2" rebar into 20" lengths (using a SawzAll). Used a laser level to project a horizontal line at shelf height and a Portalign drill guide to make sure I was drilling a 1/2" diameter hole 3" deep at right angle in center of every stud at the horizontal laser line. I sank each rebar 3" deep into the 2x4 stud. The 1/2" rebar is actually a bit oval shaped, slightly larger than 1/2" in one plane, so I used a belt sander to shape 3" of the end of each rebar into a more circular shape, and I relieved the sharp edges of the cut end of the rod so it would slide into the wood without catching.

I lubricated the insertion end of the rebar with Dove soap to make it slippery and drove it into the holes using a 3lb dead blow plastic hammer. I marked the rod at 3" so I would know when to stop driving it - otherwise you could drive it entirely through the stud and into the adjacent room.

Shelving material is 1/2" wafer board (OSB). I cut three 16" wide shelves (8ft long) from each 4x8 sheet of OSB. I laid the OSB on top of the rebar and joined the butting ends of shelves together with nailing tie plates (StrongTie HTP37Z) and 1/2" truss screws (underneath).

In spite of using the PortAlign, some holes were not 90 true and there were minor variations in the true level of the rebar sticking out of the stud. For garage storage, I did not bother to correct the issue. Although I could slip a pipe over the rebar and bend it to be level, the variations were relatively minor so I didn't bother.

Each 16' shelf is now loaded with twelve 12 gallon flip-top tote boxes, each weighing about 40 to 55 pounds, for a total weight of approximately 600lbs per shelf. They are placed on the shelves so the narrow end faces out and they actually hang over the front edge of the shelf a few inches. One wall of my garage has 6 shelves, 16 feet long so the total wall load is 3,600 pounds.

This shelf system cost me about $1.15 per linear foot (in 2013). It's not completely rigid - with the loading described earlier, the front edge of each shelf deflects downward about 1/2". The shelves bounce up and down slightly when putting boxes on them.

A structural engineer would probably not be happy that I drilled six 1/2" holes 14.5" apart in the studs of a support wall, and then loaded one side of that wall with 1.8 tons of weight.

If I was doing this for decorative shelves indoors, I'd probably use plain steel 1/2" rod which is more rigid than the rebar. Rather than trying to drill a hole edgewise into a shelving plank, I'd probably rout matching grooves in two boards and then face glue them so the grooves face each other and form holes to be slid over the rods sticking out of the wall.

Several times I had to remove rods that I had already pounded into the stud. I grabbed the rod with a large ViseGrip and pounded the ViseGrip outward with a dead blow hammer. It's imperative that the rod end has been lubricated with something like Dove soap to make it easy to insert and remove.

Obviously, this shelving system is not adjustable - or at any rate, I would not advocate drilling 1/2" holes every two inches up and down studs in a bearing wall in order to provide "adjustable" spacing.

It should be easy and cheap to do this for an 11" shelf, and probably the rebar would be plenty stiff in such a short length and less loading. I would advise using every stud you can locate.

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Interesting idea, but I think you are right in that this could present a structural problem with this many large holes in the studs of supporting walls –  Steven Jan 16 '13 at 21:00

If the shelves back into a wall, then affixing a nubbin or two for the shelves to rest on may do the trick.

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I'm not familiar with the word "nubbin" can you describe what that is? –  flamingpenguin May 21 '12 at 16:43
    
By nubbin I mean a small block of wood - around 1 cubic cm. - likely nailed or screwed into the wall. –  JoeHobbit May 21 '12 at 17:47

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