Ceiling – How much weight can threads hold

boltsceilingjoistsscrews

I'm building a pot rack that will hang from my ceiling and I want to make sure it is secure. I rigged up a hanging apparatus that consists of a 1/2" x 12" bolt, two lock nuts, a 3/8" pipe floor flange, and two deck screws. The deck screws will be directly embedded into a solid ceiling joist.

I'd like to know generally, how much downward weight can a bolt like mine hold before the threads strip and fail. I'd also like to know the same thing regarding the deck screws. I couldn't find any sort of general chart or stats online. I included pics of my parts:

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Best Answer

The 1/2" bolts will hold up your truck, or thereabouts, so that's not an issue.

I'd be concerned about the pullout strength of the deck screws (especially if your rack was particularly big or you have a fondness for cast iron). Upgrade to something a little bigger. I'd lean toward a 1/4" lag screw, 3" or so, assuming that fits the flange. If that doesn't fit, aim for a #12 deck screw. Predrill pilot holes for the screws.

A little research... in typical conditions, you can expect a 2.5" fully threaded #12 screw to hold something like 300# in pine. See the calculator at engineering toolbox.