Vertical Grab Bar: Only Two Screws?

Just watched a vid of the process and they only used a single screw at each end of the bar.
On one hand, it makes sense:
- With two holes exactly centered on the stud, the hole that is under the bar is inaccessible, leaving only the "Outside" hole.
- Offsetting the holes enough that both a top and bottom hole are accessible seems like it is flirting with screwing into one or both edges of the underlying stud.
On the other hand.... just 2 screws ????
Yeah, each screw is 2" long... but still...
Can somebody make me feel better about this?
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Pete Cresswell

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On 03/15/2016 12:51 PM, (PeteCresswell) wrote:

What size/material screw used? If it's sized properly and not something brittle like sheetrock screws, one'll hold more than your weight easily, given proper installation.
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Per dpb:

Thanks.... They're pretty official-looking screws supplied by the grab bar manufacturer, so I would trust they are sufficient.
Now that I am visualizing it, weight on the bar results in a levering force over a 1.5" lever that is stopped by the 3" diameter mounting plate bearing on the wall and transferred into trying to pull the screw directly out of the wood.
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On 3/15/16 2:12 PM, dpb wrote:

Just curious, how do you know sheetrock screws are brittle...and why are they made that way?
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On 03/15/2016 2:42 PM, Wade Garrett wrote: ...

'Cuz they snap a head off at the sign of anything hard you try to drive 'em into...and why? Because it's easy/cheap to make 'em hard if they also don't have to be ductile.
They're designed for a very specific purpose, lateral load not being included.
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On Tuesday, March 15, 2016 at 3:48:19 PM UTC-4, dpb wrote:

Agree but I think any fastener, certainly not a screw or nail, should never be loaded in shear. They should always be in tension.
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On 03/15/2016 3:25 PM, TimR wrote:

And, the bulk of the load in OP's application is, _but_ --- if load the bar by any vertical pull that fraction of the total load is in shear and when pulling anywhere on the bar besides directly over the fastener there is a least some bending moment. Can't avoid either, entirely.
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On Tuesday, March 15, 2016 at 7:50:40 PM UTC-4, dpb wrote:

If the tension force times the coefficient of friction is sufficient to be greater than the vertical force, theoretically there is no shear load.
The bending moment - I dunno, might have to give you that, but..........if the screw tension is enough to prevent movement I think it would be small.
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On 03/16/2016 11:12 AM, TimR wrote: ...

Not sure I'd give a lot of credit to the vertical friction force on a (presumed) rock wall...
"In theory there is no difference between theory and practice. In practice there is." Jan L. A. van de Snepscheut
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Years ago, before I first knew how brittle they are, I built a roof frame for a shed on the ground. It was a small 10X12 ft frame made from 2x4s. I screwed it all together. When it was all put together, I began to lift it onto the walls. By the time it was halfway up, I had a few broken apart pieces. I added more screws. Then I hoisted it up onto the top of the walls and the whole frikking thing fell apart. After I finished cussing, I had to take all the pieces and rebuild it all over. This time I used 16d or 20d common nails. That time everything worked fine!
I also bought a homemade wooden lawn chair at a garage sale. It looked nice, was made from all oak. A few weeks after I got it, I sat in it, and it partly collapsed. Sure enough, they used those goddamn drywall screws. Fortunately no wood broke, so I just replaced every drywall screw on the entire chair, with real wood screws. I still have the chair after 10 or 12 years and it's never broken again.
Drywall screws are made for drywall, and nothing more. Yea, you might be able to mount a piece of 1x4 trim around a window frame with them, but dont use them for anything that will put any load on them.
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On 3/15/2016 3:42 PM, Wade Garrett wrote:

I know they are brittle having broken a bunch by over tightening. Easy to snap. I'd never use them for anything other that sheetrock or similar non-critical application.
FWIW, Each of my showers has a horizontal bar in back, vertical bar in the front side and they feel very secure with the single screw mount. Check the specs. many have 500 pound rating, some are 250.
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Per Ed Pawlowski:

I went ahead with the single screw on each end.
This is a vertical bar 24" long.
I'm 215# and gave it a pretty good workout.
It feels solid to me.
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Back when people took pride in their work, and before everything was made to get the most profit with the least amount and quality of materials, and the least labor, they used to knotch the 2x4 studs and put a horizontal 1" (3/4") thick board wherever there was to be anything mounted, such as wall mounted sinks, towel and toilet paper bars, and so on. That began in the 1940s maybe before that, and ended in the late 1960s or early 70s.
These days, unless you build your own home, you wont find any of that. Homes are built as cheaply as possible and have a life expectency of 30 years (IF they are constantly repaired).
I expect that in 20 years all homes will be entirely made from molded particle board. Just pour the liquid mixture of sawdust, shreaded cardboard, and glue into forms, let it harden, and you have a home. But if it ever leaks, kiss it goodbye in weeks....
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On Thursday, March 17, 2016 at 7:14:00 AM UTC-4, snipped-for-privacy@unlisted.moo wrote:

Yes. Because the studs are notched, there is no shear stress on the connection of the board to the wall. There is only tension on those fasteners.
Of course there can still be shear stress on the connection of the sink to the board.
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On 3/15/2016 1:51 PM, (PeteCresswell) wrote:

I doubt it.
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wrote:

The one I put in for my mother had 2 at each end.
To be extra cautious, I didn't drill the holes big enough and I had a heck of a problem getting the screws out after she died.
And it was a rented apartment, but they were very nice and didn't complain about anything. I didnt' drill into the tile either, only sheetrock. But I put switches on the bathroom fans, pull chains, so she wouldn't have to listen to that infernal noise all the time. I just left those.
And I kept renewing a month at a time while I tried to pack up all her stuff and sell what my brother and I coudln't use, and one time I forgot to renew and when I went to do so a day or two in advance, they'd rented the apartment to someone! I didn't know what to say, but they said, Don't worry. We'll tell them they have to take another one. And they did.

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On Tuesday, March 15, 2016 at 1:51:57 PM UTC-4, (PeteCresswell) wrote:

I use a minimum of two screws on each end of grab rail. I don't want a sin gle point of failure. You can usually position them so you can get two to bite on the same 2x4 if you figure out exactly where it is behind the wall and angle the fasteners a little.
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(PeteCresswell) posted for all of us...

That's how the manufacturer made and rated it. The ones I have in my house are three screws each end. I had to block out the finished wall to my satisfaction.
Look at stair handrails. Some of the ones I've seen look pretty sketchy but work.
I am no lightweight. I see your later posting that you are happy-good.
DAGS on Sheetrock screws and there has been much discussion here on their durability (none). Work for their intended purpose. I would like to find a Z bolt to fix my miscalculations.
--
Tekkie

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On Tuesday, March 15, 2016 at 10:51:57 AM UTC-7, (PeteCresswell) wrote:

Rather OT but when my wife became disabled I installed hand grabs and long bars everyplace I could. One was a vertical grab about waist high and at a comfortable arems reach on the wall by the toilet. First time I used it I wished I had done it 30 years earlier. I highly recommend one, makes gett ing up, wiping, etc. a whole different job.
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