Screw in bending

[mpb21]

I am currently checking the following design:

A wood panel wall system using a Monarch M375 Z-Clip system (

http://www.monarchmetal.com/products/mf375-z-clips/),

where the continuous track is going to be screwed through a piece of 5/8" gyp. board to a 20GA furring channel that is running horizontally between 18GA studs @ 16" O.C.

My concern is the crushing of the gyp. board due to bearing as well as the bending in the screw due to the 5/8" stand-off. The gyp. is there for acoustical purposes and I've already been turned down when requesting that it be replaced with plywood.

Does anyone have any suggestions on how to determine the loading capacity or the gyp. or the bending capacity of a #8 screw?

Any help would be appreciate, thanks.

 

[CELinOttawa]

Sketch?

 

[wannabeSE]

Some people do not consider screw bending or gyp crushing. The only thing I have found is from OSHPD (Building Authority for California Hospitals). See the attached draft that provides a little background. Similar capacity tables have been included in there preapproved details at

http://www.oshpd.ca.gov/fdd/Pre-Approval/preapprovedDetails-dtaTable.html

. These values seem conservative and I would like to find a better reference.

 

[chicopee]

A little more work my be neede by you. Figurer out the linear horizontal load imposed by the wood panel on the continuous tracks and determine if that linear load is within acceptable limits that the sheet rock can take and if bending of the screws become an issue. I imagine that you'll have several rows of horizontal tracks on the sheet rock. To minimize the bending effect on the sheet rock, you could explore the use of inserts thru the sheet rock where the screws are to be positioned.

 

[Ron]

Use a rigid bushing through the gyp. Crushing at screw controls so increase contact area with bushing. That also keeps the fastener in shear and mitigates bending.

 

[CELinOttawa]

Just stick with the published values... Remember that theory does not always equate to safety. It is best to err on the side of caution rather than find yourself defending a skin-of-your-teeth design later.

 

[wannabeSE]

Contractor would probably prefer to install a lot of screws rather than a few screws with bushings. I am guessing the wood panel system weighs less than typical casework (upper cabinets).

I would like to find better information on sheet metal screws with bending (eccentric loading). Similar loading occurs when attaching things through EFIS or screwing channels for rainscreen through rigid insulation. How small of a load is OK. I also wonder about localized bending of the sheet metal at the screw.

 

[Tmoose]

From what I saw The monarch metal website clip selector does not list gypsum board among the acceptable substrates.

http://www.monarchmetal.com/z-clip-selector-tools/

"localized bending of the sheet metal at the screw."
yes, Shoot a 3" drywall screw thru a sheet of drywall then apply a side load.


Is that 20g furring channel one of the "resilient" acoustic designs?


there are Lots of comments about hanging cabinets on steel studs here. They seem pretty revelent to me.

http://www.woodweb.com/knowledge_base/Attaching_Cabinets_to_Steel_Studs.html

One poster there mentioned specialty cabinet hanging screws.

https://www.mcfeelys.com/search.aspx

The large flat heads would seem to take some of the stud wrinkling out of the picture, making the screw bending the limit .

"Installing a $200 box on a wall over a $20,000 copier with 20 cents worth of screws knowing that the box will be stuffed with reams of copy paper, is risky business. Blocking is the right way to go, and whoever makes the call not to install it should be the one to accept the risk."