Stud load-bearing limits

[FJ and G]

I'm sure you are sick of hearing about my layout planning by now, but tonight I pick up metal shelving and brackets from Home Depot. They aren't that expensive but the cost does add up the more you purchase. I'm planning to space them every 32 inches, since my studs are 16 on center. The shelf will be approx 3 feet wide and mostly styrofoam so I don't see a weight problem, tho I would like the shelf to support my weight as well, actually my daughter's so she can paint the backdrop.

I know that studs can handle a phenominal amount of weight because I put backerboard everywhere in the bathroom with tiles. If you add up the tiles and backerboard, each stud is probably bearing 150 pounds.

Anyone have any knowledge on load bearing? Also, how far do you space yours apart?

Dave Vergun

[Anonymous]

I have no idea what the limits are, we need a structural engineer for that. My guess is the limitation is how much force does it take to pull a screw out of a stud? I think you'll find the limit is a lot more than 150 pounds.

The studs in a load bearing wall supoprt the weight in compression. If you think about it, the studs on the bottom floor of a 2 story home with a snow laden roof are probably supoprting a lot more than 150 pounds each.

Provided you use long enough screws & are sure that the shelf brackets themselves can support the weight, I think you'll be OK.

Tony

[Big_Boy_4005]

Not any exact numbers here, but the studs load bearing capacity is enough to hold up the weight of an entire house when configured proprely!

The key in your application is the anchors used to go into the stud. Thats' s the weak link. What type of fastener, how many per stud, how well you hit the stud, and the condition of the wood have a lot more to do with how much weight your shelf can hold.

[FJ and G]

Thanks. I'm using long drywall screws but I know that they sheer more easily than long nails. Hmmmm. I may rethink the drywall screws and go with a heavier screw. Again, thanks. Sorry for taking up so much bandwith here.

[cnw1995]

We're not tired of hearing about your layout, Dave. I, for one, am eager to hear how this weekend goes. As for me, this weekend, we will add two more 4x8 foam boards in our quest to reclaim more of our raised crawlspace for the layout. Nothing like five feet of rocks and concrete to keep the trains up. It's just one big U shaped, stretched-out oval: 4 x 20 on one side connected to another 4 x 8 continuation

[FJ and G]

cnw,

That sounds interesting. i was reading a magazine about wine, while sipping some wine and wiling away my time. One article described how you can make your own wine cellar. In the article was a picture of one of them tiny bulldozers (or backhoes?), digging out another room in the basement. You can guess what I was thinking...

...more layout space, with wine storage under the layout.

With my luck, I'd hit a natural gas line and be blown sky high, or doze thru my neighbor's basement. His dog and my dog already don't get along and that would just add to our mutual grief!

[Anonymous]

The things about a screw that detemines how much holding strength it has in a material like wood are the length and the depth of the threads. A screw with deep, coarse threads will go in faster & generally hold more weight than one with shallower, finer threads.

Also, are you sure that drywall screws shear out of wood easier than nails? I have actually pulled a screw with a stripped head out of a wooden plank using a claw hammer,and believe me, nails come out much easier.

The little bulldozers / backhoes are called "Bobcats"

Tony

[lionelsoni]

Drywall screws are very brittle and not meant to hold much of a load--a square foot of drywall just doesn't weigh very much. They are popular for other purposes because they are cheap. Wood screws are not that much more expensive and a lot safer, especially for something that will be supporting persons.

A shelf mounted with screws through the drywall and into the studs may become loose and sag as the heavy load that you contemplate compresses the drywall. Here are a few ways to avoid that:

Expose the stud under the connection by removing a small amount of drywall. This would not be practical with shelf brackets, but would work with a diagonal brace.

Cover the drywall with plywood or one-inch lumber under the connections to distribute the load over a wider area.

Put a pile of washers or a spacer over each screw between the bracket and the stud, in a hole through the drywall. I have used this method successfully with a heavy stair rail.

[Big_Boy_4005]

Dave, these are the kind of topics that this forum has been lacking for so long.

Keep em comin' and we'll keep answerin!

Oh, and don't use nails , they could pull out. I'm partial to LAG BOLTS myself.[:D]

[FJ and G]

Tony,

I tend to agree w/Bob. I've unintentionally stripped the heads of drywall screws and rather than twist them out with pliers, you can break them off with just 2 hammer swings; wheras the heavier screws you can't. The other side of the coin is that drywall screws screw in easier. Solution is to predrill holes. I'll pick up some heavy ones.

Also like Bob's idea about distributing the load.

[Buckeye Riveter]

QUOTE: I have no idea what the limits are, we need a structural engineer for that.

It's time for that new game show; let's ask the structural engineer, but first some basics.

1. The sum of the forces must equal zero for static equilibrium.

2. We don't want the darn thing to even think about falling on the floor and breaking our great trains into tiny bits.

Seriously, Dave many of the forum member have given you some excellent advice, but I do have a thought or two that may help you not mutter bad words in the future.

I would suggest that your brackets be connected to the studs at every 16 inches and the reason is deflection, not of the train layout but to make sure you never see "waves" in the wall. The vertical location where the shelf attaches to the stud with respect to the floor and celing will govern the amount of outward deflection of the stud.

Several members brought up two failure modes.

1. Pull out of the attachment.
2. Shearing of the attachment.

In a technical sense they were discussing moment and shear, but I don't think some of them knew it. If you weigh say 200 pounds and sit on the end of the 3-foot long bracket, you are creating a 600 ft-lb moment. That moment is going to be transferred back to the stud by the attachments. The attachment at the top of the bracket is going to try to be pulled out, while the one at the bottom of the bracket is being shoved inward. If there are two attachments and they are 12" apart, the pullout force is 1,200 pounds for the top attachment and 1,200 pushing in on the bottom attachement. (I did these calculations on the conservative side, but in reality, one would more likely spread the load out over two studs.) If there are again two attachments, the shear for each attachment is 100 pounds, if you don't bounce around on the shelf. Using the common sense approach, how many chairs do you see attached to the wall in this manner for you to sit in? Probably less than one.

To be honest with you, the brackets you purchased from Home Depot may fail, by buckling before they pull out of the attachments unless you used some really small wood screws.

Lionelsoni advice about the drywall is 100% correct. The weight over time or during construction will cause the drywall to crush. It isn't concrete.

Also if you want your layout to be real quiet try a sandwich method of Styrofoam and thin veneer plywood. Two inches of foam, thin veneer, one inch of foam then the track. Guess what the track screws grab a hold of? Of course, if you didn’t sit on your layout to paint the background, the 16” spacing will support the Styrofoam without a metal shelf beneath it.

BTW, that snow load comment was good, real good.

[FJ and G]

Buckeye,

Your information is good but the news you bring is bad. More money to spend now on additional supports! There is one difficult section that will have to span a 6 foot window, but I will not be standing on that area or add any weight besides the foam and trains.

BTW, the studs I'm using are load-bearing studs already on outside wall of the house. Home Depot already treats me as its most valued customer.

BTW again, I had visions of the roof collapsing at the Baltimore Roundhouse with that snow on roof comment.

[Anonymous]

I didn't know about the brittleness of drywall screws. Most of the applications I've used them for were in cabinets where they were counter-sunk & the glue was really doing most of the holding.

Wood screws it is, then!

Tony

[Anonymous]

I'll add my 2 cents worth. I used to build houses so I know a little about this stuff. You shouldn't have a problem with the studs in the walls, especially if they have plywood or if the house is older, some kind of pine sheating on the outside of the stud. This building style makes for a strong wall. I would be more concerned with the metal shelving brackets and the fasteners you are going to use. The brakets I have seen are made out of some pretty thin steel, if these are like yours then I would definitely put one on every stud. Also I would use a fairly big screw probably a #10 or even a #12. In case you are not familiar with the screw nomenclature, the bigger the number indicates a bigger diameter shank on the screw, hence bigger diameter threads which leads to greater holding power. If the brackets are thin I would also use a fender type washer to help hold the bracket on the wall. This will spread the force of the screw head out over a bigger area. You should also size the screw so at least an 1 1/4" goes into the stud, so if the braket is 1/8", the washer is 1/8", the drywall is 1/2" then your screw should be at least be 2 " in length. I would probably go at least 2 1/4 or even 2 1/2" in length for this example. You should also predrill the hole as was mentioned with a drill bit just slightly smaller then your screw shank. This will make driving the screws easier and there is less chance you will break or strip a head. A little trick if you have alot of longer screws to drive is to get a bar of soap or if you have some old fashioned floor paste wax to coat the screws with either of these, it makes driving them in much easier!! Hope this helps.

[dougdagrump]

How about trying a different solution?
Two heavy firring strips lag bolted to the wall, one slightly below shelf level the second slightly above floor level. 1x3's nailed, perpindicular, to the top firring strip with an additional 1x3 glued and screwed to it( so it forms a T ). The last support would be a vertical support from the lower firring strip to the outside edge of the 1x3 T. Sounds a little complex but I think I would trust this more so than the metal brackets. Probably less damage to the walls as well.

[ChiefEagles]

If you use "sheet metal" screws, they will hold better [deeper threads] and have larger flat heads. You can add a washer to insure the brackets don't pull thorugh. Pre-drill the holes with a smaller bit to insure the screws do not split the wood. If you hit the studs, you will not hit electrical or gas as they are not in the wood. A 2X4 is 3 1/2 inches X 1 1/2 inches. I'd use a screw about two inches longer than the thickness of the bracket. Size? As big as the hole in the bracket can stand. Most "sheet metal" screws are used for more than metal now. They are the kind that come with plastic anchors for installing anything in concrete and brick. Drywall screws do not need to be used. If you want to use that type of screws, use deck screws.

[jkerklo]

The problem seems to be supporting backdrop painters more than trains.
Perhaps, paint the backdrop, then attach the shelves.

Otherwise, I would use 5/16 lag screws, with a "fender" washer, to attach the top of metal supports. A smaller screw can be used for the bottom of the support. Pre-drill all holes.

John Kerklo
TCA 94-38455
www.Three-Rail.com

[jkerklo]

More thoughts.

Instead of lag screws, perhaps "hanger bolts." These are a thing that has a lag screw on one end and machine threads on the other. They are installed by putting two nuts on the machine end and setting the lag end into the 2x4. Remove the nuts then attach the bracket.

The advantage would be that the brackets can be trial installed, then removed for the painters.

Pre-drilling the hole, and soap on the threads, is a good idea. You can break off the head of a lag screw if it takes too much force to install it. The only way to remove the broken bolt is to tear down the house.

John Kerklo
TCA 94-38455
www.Three-Rail.com

[jkerklo]

How about a test.

Get one bracket and selected hardware, install it on a wall (any wall), grab the end and lift yourself up.

If the bracket and hardware hold, you have a workable solution.

If not, then see a doctor for your back and go back to home depot for stronger brackets and hardware.

John Kerklo
TCA 94-38455
www.Three-Rail.com

[Buckeye Riveter]

[#offtopic][:-^]Let me see if I can remember the way this was told to me by my grandpa.[:D]

Several years ago before the Soviet Union collapse, the Communist Party Engineers designed and built a new bridge far out in Siberia. After the bridge opened to their amazement the locals would not cross the bridge and the rumor was that the new bridge was unsafe. Rumors of shoddy work and corruption were abuntant.

The poor peasant’s rumors were trampling the egos and the reputation of the Communist Party Engineer’s and that would not be tolerated. To prove the bridge was completely safe the engineers devised a test that all of the locals could see and hopefully the rumors would cease.

The engineers ordered the highway department to load their big dump trucks with sand and park them on the bridge. One by one the loaded trucks slowly drove onto the bridge, but all of the local drivers proceeded to abandon their trucks on the bridge and head to what they perceived as a safe location. The engineer's couldn't stand this slap in the face from the drivers and decided they would drive the last six trucks on to the bridge as if they were in a parade.

Needless to say, the sixth truck was hardly on the bridge when the whole structure collapsed sending the engineers to the bottom with their safe bridge.

[Anonymous]

Unless my memory has failed me, #2 Southern yellow pine or Lodge Pole pine studs are rated at 3,300 ft lbs load bearing when double plated.(typical residential stud wall).

Drywall Screws!
Based on a demonstration at Home Depot, Drywall screws were shown to have little shear strength---deck screws are much stronger. My problem with drywall screws is the head shearing off when backing them out of a 1x4, 2x4 etc.

[Big_Boy_4005]

John (Kerklo) may be onto something here, that would render this entire discussion moot for Dave if he was to change the way he sees the problem. This has been a very useful and informative discussion about anchoring things to walls, but what if the back drop was a seperate panel that could be painted in a position that was convenient and comfortable for the artist, and then set into place.

The mountain comes to Mohamed, Mohamed paints the mountain, the mountain returns to it's proper place.[(-D][swg]

This of course is not conventional thinking, nor common practice, but rather, part of the beauty of a forum such as this!

The exchange of ideas!!

[:D]

[Buckeye Riveter]

Big Boy I agree 100% with the logic of painting the background first and then putting it into place and not using the shelf as a place to locate your or your loved ones derrières.

[lionelsoni]

Frank advised that electrical wiring and plumbing are not in the studs. Jeff advides that screws penetrate the studs at least 1 1/4 inch.

Actually, horizontal runs of non-metallic sheathed cable (NMC), which is what almost all houses are wired with, normally go through holes drilled through the centers of the studs. The National Electrical Code requires that the holes be kept 1 1/4 inch from the stud's surface, unless covered by steel plates. So the screws should not go into the studs any more than 1 1/4 inch, although I would certainly try to use all of that.

SYP and other strong woods are not often used for studs. In fact, "stud" grade is one of the lowest. Walls fail not in compression but by "Euler" buckling, which means that they bow out from under the load. The sheathing (even drywall counts) keeps the studs from buckling in their most vulnerable direction, within the plane of the wall. Their stiffness keeps them from buckling in or out. The buckling problem limits their capability to well under what would be expected from their compressive strength, which is why they can be built from cheap wood.

The complicated bending load on a stud supporting a shelf layout is quite different from what it bears in holding up the house and would be difficult to analyze; but I would be pretty sure that it is negligible. As several have said, the fastening is the thing to worry about.

[FJ and G]

Thx for more info. I measured the holes that conduct the wiring thru the studs, factored in the drywall and screw sizes before attaching the shelving. Everything worked out. I'll post something about how the construction was performed.

Dave V.

[FJ and G]

btw, We are going to probably paint separate panels rather than labor over the shelf. I DON'T want the painting before the layout as I want the layout to blend in.