melamine shelf deflection (long)

[loutent]

I would like some expertise on this.

We have this pantry in our kitchen which SWMBO wants reorganized/re-shelved to make it more useful - right now (and for the last 18 years), it has had fixed particleboard shelving of various depths.

The pantry space is 24 (deep) x 30 (wide) x 96 (high) and a 24 inch door for access.

I am thinking of buying (1) - 16x96 drilled melamine sheet and (1)

12 x 96 drilled melamine sheet - each of which I would crosscut to give (2) 48 inch sheets of each width. The 16 would rest on the floor on either side of the pantry while the 12 would rest on the 16's - all screwed to studs. Then I would use standard 3/4 melamine for the adjustable shelves - some 16's & some 12's.

I would support the adjustable melamine shelving with metal shelf pins (1/4 inch) - and no back support (gulp!?)

Would such a shelf support a double high, triple deep of my Campbells Chicken Noodle (i.e. say, 50-75 pounds each if needed?)

I DAGS (see link at end) and came up with this interesting chart.

If I understand this correctly, a 30 inch span of 12 inch melamine will support 350 pounds before deflecting 1/4 inch. They don't mention 16 inch x 30, but from the chart, it looks like it would hold even more weight before deflection.

Any thoughts - besides the fact that I am over-thinking this?

Thanks!

Lou

Here's the chart:

-------------------- Shelf Deflection of 1/4" by Estimated Total Distributed Load in Pounds

This table shows loads that cause various 3/4" unfixed 8"- and 12"-wide boards to sag 1/4" when spanning 30", 36" and 42". Loads required to cause sagging less than 1/4" may be estimated by direct proportion. For example, the load required to cause a 1/8" sag is one-half that of the values in the table.

-------------------------------- Material Span

30" 36" 42" Material Width 8" 12" 8" 12" 8" 12"

-------------------------------- Red Oak

356 534 209 313 133 206

-------------------------------- Medium Density Fiberboard (raw or covered with melamine)

100 150 58 87 36 54

-------------------------------- Birch faced plywood, veneer core

145 218 86 129 54 81

-------------------------------- Birch faced plywood, particleboard of medium density

125 188 72 109 46 68

-------------------------------- Particleboard of medium density covered two sides and one edge with nominal

0.050" high pressure decorative laminate 234 350 137 205 86 129

-------------------------------- Information provided by the Department of Wood Science, Division of Forestry, at West Virginia University for the Architectural Woodwork Institute.

--------------------------------

Check it out at (watch the wrap):

[bob]

I find it hard to believe that a 12" x 30long sheet of melamine only deflects 1/4" with a 350 lb load. I would at a minimum add a 1" lip across the front of each shelf for strength, and I would make the strip out of real wood, say some poplar, painted white to match the melamine.

Why not build some really nice shelves out of stained oak? You wouldn't need any additional strength strips, etc.. with oak, at least over 30 inches.

Bob

[Tom Watson]

At my local Borg (HD) they have glued up 3/4" Pine stock that they sell as closet shelving.

Pecky as it may be, it will hold your soup cans up without complaint.

It's a damned sight more attractive than melamine, and it has that organic thing going for it.

Amen.

Regards, Tom.

"People funny. Life a funny thing." Sonny Liston

Thomas J.Watson - Cabinetmaker (ret.) tjwatson1ATcomcastDOTnet (real email)

[stoutman]

Try:

stock = MDF.

[Old Nick]

On Thu, 02 Dec 2004 21:25:17 -0500, loutent vaguely proposed a theory ......and in reply I say!:

remove ns from my header address to reply via email

Only opinion.

There's the problem. That 350 lb is for quite e differetn material than the average "melamine".

(average hardware melamine)

is not in any way

I would think. The second one looks as if tht e skins provide a serious "sandwich" stiffness.

There is also the matter of time. Particle board is notorious for bending slowly over time. I would place a lip under that self, and / or support it at the back.

[Old Nick]

On Thu, 02 Dec 2004 21:25:17 -0500, loutent vaguely proposed a theory ......and in reply I say!:

remove ns from my header address to reply via email

More thoughts.

In that test they do not show what sort of load it was, nor do they show how it was distributed along the shelf. Silly. I would take those tests very carefully.

Load carrying goes up proportional to the width. But all this assumes that the load is not all at the front or back of the shelf at any point.

On the time thing and bending. I have a _empty_ unsupported shelf ion one of my sheds. It is bent about 2" along its 48" length. Empty.

One way to stiffen shelves enormously without any added beams is to rout out a couple of 1/8th inch slot along the front and back and insert a 1/8th steel "beam" on the underside of the shelf. You could probably even go shallower and use steel strap; 1/16th or so. It has to be glued very thoroughly, probably with epoxy, and several screws would not hurt. Lots of work, but useful in the needed places.

[Doug Miller]

[snip]

You _don't_ understand it correctly. See below.

[snip]

"Nominal 0.050" high pressure laminate" is _not_ the melamine layer on home-center particle board. That's talking about _Formica_.

Notice the thickness: 0.050. Fifty thousandths. The melamine layer on home-center particle board is more like four or five thousandths thick. It's nowhere _near_ fifty.

No way is melamine board from Home Depot going to support weights like that with only 1/4" deflection. No way. You're much more likely to see actual weights like those quoted for MDF:

but IMO even those are suspect; they seem kinda high.

Why not just buy one piece of the stuff, support it on blocks 30" apart, and start loading soup cans on it? That way, you can directly measure the actual performance of the material you'd be using -- and if it sags too much to suit you, you're only out a few bucks. Heck, if your testing doesn't put a permanent bend in it, you could even return it and get those few bucks back.

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter by sending email to autoresponder at filterinfo-at-milmac-dot-com You must use your REAL email address to get a response.

[J]

It is not overthinking. No one wants to have saggy shelves. It is a good idea to design them so they will work.

However, the numbers you have are NOT for the material you want to use. There are three basic ways you can make a sturdy shelf:

1)Use very strong materials (this approach is usually not so cheap)

2)Make the shelves thick (lots of ways to do this, one easy way is a thicker band at the front edge. Others are to make a sandwich with thin top and bottom and a rigid structure inside - some call this a torsion box- it is time consuming though)

3) Support them more often. A full length ledger to support the back is the quickest and cleanest way to do this, though vertical supports are also a possibility.

Obviously you can combine these approaches to achieve whatever level of strength you need, but what you are describing will not give you a satisfactory shelf. By adding a ledger at the back I'm pretty sure you can get by with the material you have. How often are you going to change the shelf spacing in the pantry? I'd be willing to bet that 90% of adjustable shelves get adjusted only once and that is when they are first installed. There is no need to make it adjustable.

-j

[loutent]

Thanks to all for the input.

I'm pretty much stuck with melamine since that's what SWMBO wants (easy to clean), so with all the info provided, I think that I will use it but add an oak strip in the front to add strength/rigidity.

I sort of thought that the laminate mentioned in the chart I posted was not the melamine we buy at the BORG, but I needed to be convinced of that - thanks!

I have some scrap melamine in the shop, so I think that I will set it on some blocks about 30 inches apart and then put about 10 gal of H2O on it - let it stand for a week or so, & see what I get.

Almost every adjustable shelf we have (many!) have never been adjusted. On the other hand, the customer is always right ;->.

Thanks again!

Lou

[mac davis]

I built a bookshelf for the kids games years ago and made the mistake of using 5/8" particle board for the 36 x 12" shelves... SAG..

I thought about the edging thing, but figured that the kids would have trouble with the lip.. What worked very well was to screw & glue a 36" long 2 x 1" to the BACK of each shelf, underneath it.. it moved with the shelves when they were adjusted and there wasn't a lip to snag things... also, very few people use that last inch or two under the back of a shelf.. YMMV

[mac davis]

of course, you could use laminate counter top for the shelves... strong, and easy to clean.. lol