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" wrote in message
...
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):
http://www.woodweb.com/knowledge_bas...tallations.htm
l