Lab storage shelf collapse: postmortem

[dfnr2]

Hi all,

I recently experienced a bit of a disaster in the lab.  When I moved in, I had a carpenter place 24-inch deep shelving about 8.5 feet high around the circumference of the (small) lab, a converted 1-car garage.  They were supposed to hold 100 lbs/ft.

About a week ago, one section gave out.  My wife heard some noise, and came into the lab to find a pile of heavy vintage computer wreckage on the floor.  Some of it hit the workbench on the way down.  Luckily, it looks like the equipment slid forward off a sagging shelf, rather than drop straight down, and nothing seems to have hit the RF test equipment on the bench below, although some accessories were knocked around.

In retrospect, the design was flawed.  The sagulator sag calculator indicates that for a 24 inch depth, 1 inch thick plywood material with a 1x2 inch edge should be able to support up to 100 lb/ft with a floating configuration (not fixed edges), and center loading (more sag than uniform loading), as long as the supports are no more than 36 inches apart. This design used 3/4-inch MDF, with some of the supports spaced 48 inches apart, and no edge strip.  The sagulator predicts a sag of 1.56 inches, which is dangerous.

I’ve attached a photo (below) of the design.  This is the section of shelf adjacent to the collapsed section.  You can see some space where the shelf is separated from the wall, no longer supported by the MDF strip on the wall.  The shelf was only held to that MDF strip by some thin nails.  I would think some glue, but I don't see signs that the edge of the MDF ripped off, so I am thinking no glue.  The separation is new, and I suspect it’s due to recent extreme variations in humidity (and to some extent temperature, but the lab is climate controlled.)

So now, I have to take down all the equipment from the shelves around the room, and place them in storage.  Then I have to replace all the shelving.  This time, I’ll make sure that proper brackets are used.  I was thinking something like this, or something standard like the unistrut system.  The shelves will be 1 inch plywood with 1x2 edge strip, and supports at least every 36 inches.

I've also attached a couple of photos of the bench below the failed shelf.  I apologize for the state of the lab here.  Normally it's reasonably tidy and clean.  All the debris is from the fall.  Also, I was recently given couple of computers, including an Apple II+, which I had on the bench for repair, adding to the clutter. 

Here’s how the equipment fared:

- IMSAI 8080: several broken front panel switch handles.  The case otherwise looks fine.  The boards were not installed, and were bubble wrapped, so they are all still in good shape.  Will have to power it up and make sure it is still OK, but I'm optimistic. 

- SOL 20: right wood panel sheared off the bolts and scratched.  The left wood panel is still attached to the base, but dented (flattened) at the front upper corner.  The panels had been pristine before the fall.  I will see if I can find a way to restore them.  Otherwise, I will try to make some replacements.  The metal case itself is in great shape, as are the internals look great, but there’s no video, so this will be a project.  I’m optimistic.

- HP 9830A computer:  heavy as a tank.  The keyboard bezel is plastic and the front part is smashed, along with the spacebar.  Several key caps have popped off, and some are broken, but the key switches still work.  A couple of key stems are broken.  I plugged it in and powered up, and it gave me a prompt, and I could type.  So, just keyboard repairs and cosmetic fixes.

- Infotek FD-30 disk drive.  This went with the HP9830A.  The front bezel is a bit cracked.  I don’t have the cable for this, and so have not previously verified this was working, so if it doesn't work, I can't necessarily blame the drop, but I think I will have to check the mechanism and realign.  I was able to find the biggest piece of the broken-off plastic and superglue it back.  Only a tiny defect remains.  I powered up the drive and the light comes on and the drive whirs.  I’ll have to make this a project to get it working with the 9830A.

- HP 9866A - This one face planted, and it looks like this printer broke the fall of the FD30A drive and HP9830A computer.  The front plastic part is smashed to tiny bits and the mechanism make a sick grinding sound when I apply power, so I think this will be a parts unit.

- HP 9836C - Luckily, the monitor did not implode, but the monitor case is cracked.  The monitor fan comes on when I power up the unit, but no display.  Not sure which part is the problem.

- Commodore PET 4032 - This one miraculously landed with minimal scuffing and no dents.  The monitor is just fine.  I powered it up and got the BASIC prompt. The display is nice and clear.  Inside, everything is tight and locked down.  Most of the keys don’t work well, but that’s because the keyboard needs cleaning, not because of the fall.

- Apple II+ - This was on the bench, and the shelf contents hit the Apple, and the power supply which was out for repair, on the way down.  Four keys broke off the keyboard.  I found what looks like replacements for the ALPS switches on AliExpress and have ordered them.  Also, the power supply case is badly dented to the point where it won’t go back together or fit in the Apple II case, so I’ll look for a donor power supply case somewhere.

Anyway, I thought I’d share this as a cautionary tale, and also share a bit of misery, since my family and friends don’t share the hobby and can’t really commiserate. . .

Cheers,

Dave

[cruff]

Looks like the door rail was bent by the equipment on the way down.  I'm really surprised that screws weren't used to anchor the shelves to the rail.

[schmitt trigger]

We in this forums, as your brothers in Instruments, DO feel your pain.
Specially since some of those are mostly irreplaceable.

I also have suffered a similar shelf colapse, although the damage was far less. The only irreplaceable component which I still mourn was an Arcturus blue-glass vacuum tube.

Hang in there, bro.

[SilverSolder]

Are those supports held with just one screw on the bottom?

[aargee]

So it let go at the back of the shelf proper, then pivoted on the brace where it attaches to the wall?
The turning moment where the weight of your gear would then be putting excessive force at the back of the shelf a few nails or screws for that matter aren't going to take it over time. The supports should have been full triangles with the vertical sections firmly attached to noggins.

A PITA with 20/20 hindsight, I've made a few shelf assumptions in the past too that have turned into educational sessions.

[Shock]

That is sad to see and I still feel nervous for the little HP voyager sitting there on the table. Perhaps attaching to beams or joists will give better additional support, personally though I'd avoid anything but steel racking from the ground up.

[TerraHertz]

The supports should have been full triangles with the vertical sections firmly attached to noggins.

Noooo, not the noggins! Those can't be trusted either, since they may be only attached to the vertical studs with inadequate nails. They are _supposed_ to have at least two big nails each end, but builders are lazy. Even in my own owner-built (by me) workshop I don't trust them.  Massive screws (see pic) into the studs, and nothing less. In some cases even bigger coach bolts where the bolt has to take sideways force as well. Even then with so much weight on some shelves I worry about the 2x4 studs breaking under the torsional load. Metal racks direct to the concrete floor, are the only structure I'm fully comfortable with.

But in OP's situation he can't do that due to the garage door opening path.

[rdl]

I don't think MDF was a great choice for the shelving material. MDF is basically just sawdust held together with glue. Seems like 1/2" plywood would be both lighter and stronger.

[basinstreetdesign]

Wow, that's a serious collapse. 
And yes you have to take it all down and rebuild it.
If it were me I would make sure that each and every one of the triangle supports is built with 2 x 4 material and screwed into a wall stud with 3 or 4 4" #8 wood screws.  That means one support every 32 inches at most and some or all only 16 inches apart.  And definitely 1" plywood not MDF for the shelf.  I built my bench from 1/2" MDF and regret it even though there's been no trouble yet 
Can you imagine if it had come down on your head?

[edy]

The problem is those 45 degree wooden supports. I would rather use something like a metal angle bracket screwed into every stud along the way, deep into the stud with several screws. See attached image. It is not the MDF that is the issue. It is those large wooden 2x4 cut with 45 degree edges and held into the wall with single screws. They put too much strain on a single screw and rip it out of the wall. Having an L-bracket with a few screws along the stud will greatly reduce the ability to shear off the screws.

You can see also attached an image of shelving up in a laundry room. Screwed into every stud, all along the entire length of the shelf. You need them to avoid having the shelf "sag". If you prefer you can use the ones that look like a triangle, also metal, instead of L-brackets. They are even stronger. If needed drill a 3rd hole along the vertical to screw it into the stud with 3 nice size screws. It won't move, every stud, you can hang your entire weight from it. I still think it was those wooden 45 degree "supports" for the shelf. I never use those, and if I do I will always brace it beneath at the stud with additional horizontal beam (like you have at the top under the edge of the shelf) to avoid it slipping down. Honestly the metal brackets are cheap and easy to install than cutting wooden 45-degree supports and will be stronger.

[med6753]

I'm no carpenter and I didn't stay at a Holiday Inn last night but IMHO that whole structure is flimsy and I wouldn't trust it to support 50 pounds, let alone 100 pounds. Either your carpenter was a total idiot or he didn't understand your requirements. Here is what I would do:

The strip along the wall is inadequate. It only gives you .75 inch mounting surface. Plus I don't see any evidence that it's lag bolted to the studs behind the wall board which in typical structures is 16 inches on center. Maybe it is and I just can't see it. Anyway, the strip should upgraded to a 2 x 4 which will give you 1.5 inches top mounting surface.

Shelving: 0.5 inch MDF is OK. 0.5 inch plywood better. But I would consider .75 inch plywood. Firmly bolted with wood screws, not nails, every 6 to 8 inches or so to the top of the strip WITH wood glue.

Supports: Those supports are completely inadequate IMHO. It appears by the tear out that the carpenter simply used wall anchors in the wall board. There should be supports every 16 inches bolted INTO the wall studs.

Additional safety: Consider using steel strapping at each corner from the ceiling to the shelf similar to what's used to support the garage door rail.

As I said I'm no carpenter but I do have some experience wood working as shown by this entire bench arrangement built by me.

[Berni]

Dang that is quite the carnage.

The design is not all bad tho. This sort of 45 degree support can be incredibly strong and does not need any massive screws to hold the support against the wall, just needs to be held from slipping along the wall.

The problem is that the top surface becomes part of the structure with such 45 degree supports. Loading it up causes the back of the shelf to be pulled away from the wall with significant force. There is more forwards force that downwards force on the back side. This is where you need big ass screws holding it into the wall. So the carpenter used crappy weak nails in the most heavily loaded joint.

Okay the top surface being MDF is not great too. It needs way more supports to get anywhere near 100lb/ft. But then again MDF does give a fair bit of warning beforehand. It would sag more and more if overloaded letting you clearly see its overloaded before it would actually break.

Plywood is certainly a better choice, but you could still fix up your shelves by putting in a crap ton of screws in at the back end and adding a few more 45 degree supports. MDF can tear a corner out under a lot of tension so the screws really need to be pretty narrowly spaced along the back. And yes glue is always a good idea (Also why a solid wood strip along the front is a good idea).

[Ian.M]

I wouldn't trust screws in holes too near the edge in MDF.   Even if it initially looks ok, add some condensation and temperature cycling and the expansion and contraction can 'fret' the MDF against the screw  shank resulting in delamination, and a massive loss of strength, so it tears out between the hole and the edge under load.  Also, gluing MDF in sheer isn't that reliable for similar reasons - the face layer can delaminate and tear off. 

I agree with med6753's comment about the depth (front to back) of the batten the rear shelf edge lodges on.  There is *NO* way to fix that without replacing the batten, as screw holes will either be too close to the edge of the MDF or too close to the face of the batten.      I'm with the 'Triangular metal brackets and plenty of them' crew on this, with looooong screws into the stud at the top back corner of each bracket, so the MDF doesn't carry the cantilever forces pulling the shelf back edge away from the wall.

[GreyWoolfe]

I would rebuild with something like these.



These 8" by 10" brackets will support 320 lbs per pair.  I used the bigger brothers to build my 'L' shaped desk and they support 600 lbs per pair.  They are available at Home Depot.

[Berni]

Yeah when i build shelves i just get metal brackets for the job and put a good strong piece of wood on top.



I use this design a lot. Comes very usefully when you want multiple shelves on one wall since the height can be adjusted on the fly to the requirements. And they come in pretty beefy versions that can carry a lot of load. I mount the rails onto solid brick walls with plenty large screws into inserts and its rock solid.

[Gyro]

No tear-out at all visible to me at the top of the back rail  . Looking at the shelf to the left, it just looks like a glue line, and one that didn't 'take' very well!

[Dielectric]

I put up storage shelving in my garage, and used 1/2" plywood ripped the long way, with 2x4 framing underneath.  Lag bolts to the wall studs at the back through the 2x4, and steel strap to the ceiling along the front.  It's strong enough to hold a full set of wheels and tires for winter changeouts, in fact if I get up there it doesn't even make a noise.  I'd feel comfortable sleeping on it.  The problem, if there is one, is that the 2x4 framing is probably overkill but I can also hang stuff from those rails with screw hooks, like bikes, without worries.

I also made some 4' wide shelves in a rack to hold tools, paint cans, etc.  There, I used 1/4" MDF sheet for the top surface, a torsion box frame of 1x2 furring strips glued and screwed, and a thin Masonite skin for the bottom surface.  That's a 4' span loaded with gallons of paint for about 10 years with no visible sag.  The only support is at the short ends, 1/4" steel dowels set into drilled holes in the 2x4 uprights.  It was a complete PITA to build but I liked the engineering enough to persevere.

[ebastler]

1/2" plywood ripped the long way

Hmm... In plywood, I would expect to find n+1 layers grained one way, and n layers grained at 90 degrees. For 1/2" plywood, n+1 becomes about equal to n...

So I don't think the cutting direction matters much at all, except for looks. But of course it looks "right" if the outer layers' grain runs the long way! 

[jmelson]

I don't think MDF was a great choice for the shelving material. MDF is basically just sawdust held together with glue. Seems like 1/2" plywood would be both lighter and stronger.

YES, ONLY ONLY ONLY use plywood.  No MDF or OSB (oriented strand board) these have no great tensile strength, and also sag over time.
The plywood is screwed into 2x2 lumber, and NEVER screw into the edge of the plywood, always drill through with screws at right angles to the sheet.
I built a set of shelves that fit on top of a steel bench 30 years ago, it is showing no signs of sag or weakening.

Jon

[aargee]

The supports should have been full triangles with the vertical sections firmly attached to noggins.

Noooo, not the noggins!

Not a builder am I, I meant those vertical ones - studs.

[Shock]

Not a builder am I, I meant those vertical ones - studs.

I think we can all learn from that, don't nail into a noggin, screw into a stud.

[Johnny10]

You've got some great equipment ! Tek 370 Cool.

That was not built by a real carpenter.
Those shelves wouldn't hold heavy clothing boxes let alone heavy Tech equipment.

Any carpenter would know that.
Whenever you get away from Post and Beam type construction careful attention must be paid to support spacing and proper fastener attachment.
Been a carpenter for 35 years.
Seen lots of hobbyist carpentry over that time.

Sagulator??  Come on. Just imagine if your house floor was constructed the same as your shelving.
Typical home floor construction is rated 40psf.
You would be in the basement.


You need to be using at least 2 x 4's with no more than 24" Centers. And angled supports that are properly fastened. MDF is fine as long as there is proper support spacing. If your trying to make design with no supports going to floor from front of shelving you might drop threaded rod from the ceiling.

Save that great equipment.
I want to know how you get the heavy equipment up there? Without hurting yourself?

Looking for effective designs with no supports intruding on floor space, I found this pic.

[joeqsmith]

That's too bad.  Looks like the next shelf down didn't take much of a hit.  I use that portable steel wire shelving.  I think they rate it to 500lbs per shelf and it provides a lot of air flow.    What model LeCroy? 

[soldar]

Use strong brackets fastened securely into studs.

Space them closely.

If you are using mdf or if the distance between supports is too great then you should reinforce the underside of the shelf with one or several strips parallel to the wall.

I am always surprised by how badly people judge and how undersized they build things. I always overbuild and never have problems.

[SilverSolder]

You can make strong shelves out of inexpensive 2x4 lumber, but the carpentry has to be taken a little more seriously if you need heavy duty capabilities.