i know folks here talk about beam loading, both steel and
wood. i am building several large wall mounted shelves in
a frame home. they are metal L-brackets rated at 500-600lbs
each, topped with 3, 4 or 5 2x4 studs.
there is no spec, or minimum load for these shelves, just want
them to be heavy duty and safe. the brackets vary in width,
16-20 inches. this accomodates between 3 and 5 2x4's on their
side, with some amount of spacing between.
i would rather use 3 & 4, rather than 4 & 5 wood members, if
the wider spacing is no problem. this leads to the question:
with support at 32" intervals, how much load can a 2x4
support on its side?
btw, i am using 5/16"x3" lag bolts to fasten the brackets.
it's "HEM FIR", Hemlock Fir, about the cheapest "stud" on the market.
these are about "util" grade, there is one about a dime cheaper at HDepot.
if there is a grade stamp, it must be, "STUD-R", manufactured in Cowlitz,
Wa. Thanks! --Loren
That really only means both Hemlock and Douglas Fir are in the pile .
Pretty common . If you can hand pick , find stuff with as small of
growth rings as possible . You ask how much will it support on its side
? I take it you mean on its edge ? The best way to make sure you get max
support is to have the cross braces supported from underneath rather
then simply screwed to the standing support . Look at real old wooden
ladders . You will see where they add small blocks of wood between the
rungs . I think this will double or triple your max loading . Good Luck
Try the Sagulator
Usual limit on timber shelving is visible sag, not breaking load.
What ? Me ? Evil Dictator of Iraq ?
Nah mate, I'm just a Hobbit, honest
My calculator comes up with breaking load of 150 pounds in the
center of a softwood 2x4 laid flat on 32" center. This is the
same as 300 pounds equally distributed (row of books) I wouldn't
go more than half that. 2 studs would be OK for lightweight loads
(Christmas wrapping paper?) use 3 to have a bit of safety factor.
Deflection is not really an issue in this application, who cares
if it sags a bit? But the sag will increase over time, usually at
least half again more than when you first load it.
Keep in mind that stud grade lumber is not rated for the sideways
load on the weak side since the sheetrock keeps it from moving in
that direction. Look for any shakes, splits, etc. I've been able
to easily break some of the cheap 2x4s with a quick snap over the
knee. Take each one and slam the other end on a concrete floor.
If it 'boinks', fine, if it 'buzzes' put it back. Don't be
surprised if some break.
BTW: text books are some of the heaviest things you can put on a
shelf. Those nice engineering text books run about 6 pounds per
inch of shelf!
Loren Coe wrote:
hmmmm, i am already considerably over that on my first shelf. the
"woodbin sagulator" that Roy suggested shows a 0.16" sag for "West.
Hemlock" with 600' in the center with another 50% sag overtime. my
guess is that is close to the breaking point.
my first load is about 450 lbs on 4 members with no visible sag
across the 33" span. another span of 40" is sagging on just the
front member, about ____ with about 1/2 the load. this may be
explained by an overhanging box that puts more load up front, plus
that first member has no help on the outside. this makes me think
again about the placement of that member, i have been overhanging
the bracket about 1.25" (this makes a 16" shelf on a 14.75" bracket).
well, thanks to all for the feedback, i am taking it slow on this
project. here's hoping i don't make the Dallas Morning News, "Man
dies of broken nose, neck, and spine when tractor engine falls from
top shelf." <grin> --Loren
For really heavy stuff, the Z-bar shelving units available at Home Depot or
Costco are hard to beat. They cost about $90 per 6' section, IIRC. In a
garage/warehouse, pallet racks are extremely strong and available used at
Engine blocks ... I don't like the idea of hanging your shelves from wood
stud walls using lag bolts. Much to be said for a straight vertical support
from the floor.
You're in the general neighborhood, I think. Boeing almost always has 500
lb load per shelf industrial shelving, $1 per shelf, cheap if you use plain
angle stock for the uprights instead of buying the posts ($10 per post, 2
posts to "start" and 2 posts per running section). I have a couple
thousand square feet of the stuff. Forget the clips, just assemble it with
5/16x1" bolts and nuts.
ENGINE BLOCKS???? Sheesh!
Your numbers sound about right. I used some strength numbers for
the more junk varieties of studs. Keep in mind that all of the
strength numbers used in the building tables are for multiple
member applications which means the AVERAGE. Some are higher,
some are LOWER. If your load is all on one, you are at risk.
Another comment: there is a lot of difference between 32" and 40"
if you are talking about a distributed load. (less if you are
talking about point load, that relationship is linear)
I have some similar shelves, I had some left over 2x12 in
Southern Yellow Pine. Two of those are heavy duty!
Loren Coe wrote:
that may have been an overstatment. i have built a deck in the
'attic' of a large garage that held about 2 tons, all wood. i
never felt at risk when pawing thru the contents. ymmv.
that is encouraging, and i understand about hand selecting, some-
thing i cannot imagine _not_ doing. the "whacking" test is new
to me, tho. it must thrill the "associates". i am not sure if
i am up to that, maybe just drop them?
yes, that url i mentioned shows a wide variation in "sag", 32 vs
42 inches - much more than the geometric variation. as said in a
previous response, the "normal" spacing s/b 32".
these brackets are hefty, Stanley and National brands, some made in
China (the L member varies from 1/8-5/32", but the brace is always
5/32/"). the apparent quality varies from batch to batch, they seem
to change from "steaking" to welding the brace. i can easily hang
from any one of them, at about 210 lbs, even chin myself.
Hold the 2x4 level at waist height, hold one end, drop the other.
Tell the 'associate' that you are a klutz.
The 'whacking' test is quite interesting. You can definately hear
the difference between a solid one and one with flaws. I did that
with a batch of used wood fence posts recently. The good ones
went 'bonk', the bad ones 'fuzzzzz', and the really bad ones just
snapped. I lost almost half the stack! But better that way then
digging more post holes. (at 20 minutes apiece in hardpan clay!)
I'd handselect the lumber for even grain and so forth as any knotholes will
seriously weaken the strength of the lumber. Better is to get a better
quality lumber that is used for roofing.
Next is that you don't want to do is to screw the lumber together. Better
is to support the beams so that you could put the shelf together witout
fasteners and it will stand (until some side forces knocks the mess down) by
itself. Screws, bolts and nails, etc. are nice but they shouldn't be doing
the heavy support as they are localized loads and will be in shear which
will quickly crush the wood in the area of the fastener.
"Fancy" joints were used in the old days for a very good reason, they
allowed the jointing of wood without the need for the expensive metal
fasteners of that day. The wood was supported by the joint and nails or
pegs were used to make sure that the odd load didn't pull the joint apart.
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works evevery time it is tried!
i hope the hell not. i possibly overstated the intended load, that one
33-34" section was pretty much the max, and not typical. the 40" section
was probably unique, against a plumbing wall, which actually speaks to
your point. those walls are pretty chopped up and even tho 2x the width,
are a worry. hopefully, i will hear some kind of creak or groan before it
completely collapses. :-(
there will be only a single shelf of the type i have described, but
definitely made to take a load. if i can relate the "sag" data to
some "limit" data, that would be useful. otherwise i plan to keep
an eye on things and an ear open. escpecially since another poster
cautioned the same as you. Best Regards, --Loren
ps. aren't you going to miss the Great NW? a brother and grandfather
both worked for Boing, the So. Seattle plant.
As was stated before, it is not sag you need to worry about but
load capacity. Wood is pretty flexible so in a building you
ususally run up against the sag issues before the load
considerations. Here it is all about load. And load issues tend
to be catastrophic.
All the lumber is sized for house building things done in a
'standard' fashion. You are using it completely differently.
There is a beam loading calculator that some of the NG guys use
(I have a different one), see if someone will give a URL for it.
Use these values for a 2x4 laid flat:
Section Modulus = 1.3125
Moment of inertia Fb (max stress) = 900 psi (pretty variable!)
Youngs Modulus (elasticity) =1,000,000
Loren Coe wrote:
Hopefully it isn't also a bearing wall that is holding up a lot of
vertical live and dead weight load. If the shelf pulls the wall out
of vertical with the plumbing notches in wrong the side of the stud,
it can collapse in buckling mode due to induced eccentricity with,
maybe, a few milliseconds warning. Buckling is a truly nasty failure
I don't know what the wall's role is in the structure, so this may all
be worrying about nothing.
Since I've been doing a lot of structural calculations to firm up this
house design, I've gotten a whole new respect for their structural
integrity, and, possibly more importantly, how it can be screwed up.
The traditional framed house is a really forgiving structure, most of
the time ...
hummm, it's a not bearing wall. hopefully, the ceiling sheetrock helps
to keep the top plate from moving. i can see now that some extra caution
s/b exercised here, tho. possibly strapping the entire length of the
studs being compromised. at the very least, be _sure_ that all three
lag bolts bite into solid wood. if not, install a strap at that loc.
your comments reflect mine and my brother's experience. i have always
wondered at the performance of connections made with simple nails, often
key members of the roof structure. the nail gun w/glue coated nails seemed
like a real improvement. later i heard that is not always so, the nail
heads came under suspicion, too small or countersinking seemed to be the
issue/s. they were suspected of pulling thru or seperating during earth-
quakes in California.
my brother built a house with engineered timbers, the "I" beam type, and
due to his own lack of knowledge, had big problems with record snow loads
(in Montana). for this one reason, if i were building a home of any
size (read $$$$) or using engineered beams, i would have an architect
sign off before starting. just mho. good luck! --Loren
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