4

I am building some industrial style shelving for my office. Basically I need to know how much weight can one 2 inch screw in a stud hold? This will answer my question. Thanks.

closed as too broad by isherwood, Tyson, Daniel Griscom, ThreePhaseEel, mmathis Mar 19 '18 at 13:11

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 3
    You'll need to give more details on the design of your shelf and the use of the screws to determine what kind of loads the screw will be under. Load capacity caries with shear loads (i.e. like with hanging a picture), and pulling loads (i.e. leverage action of a shelf pulling the screw out of the wall). Most shelves will have both types of loads, but the design of the shelf will help determine the type of load. Also, how much of the 2" screw will be into the stud? – Johnny Jan 11 '15 at 16:43
  • 1
    Two more important questions that need to be asked. What is the diameter of the screw? Is the screw installed in a correctly sized pilot hole or is it simply jam screwed into the stud. Both of these also greatly impact the answer to this question. – Michael Karas Jan 11 '15 at 17:57
  • 1
    Another thing to consider is that you should never design a support system for a load that is calculated right up to the capability to the last screw. You should always go for 3 to 4X the rated capability of fasteners to assure the biggest safety margin. The last thing you need is for the industrial style shelving to come down on top of someone. – Michael Karas Jan 11 '15 at 18:01
  • Also to be taken into consideration is the quality of the screw alloy and proper tempering thereof. I've seen cheap stuff that snaps off just in the act of tightening 2" of threads into Douglas Fir and I've seen structural screws that have guaranteed published tensile and shear strength and tables that delineate the type of wood and the expected holding power. – Fiasco Labs Feb 11 '15 at 4:27
  • 1
    The other factors not being mentioned is the fact that the screw will have a piece of drywall in between it and the stud. This will have more impact on the screw than almost any other factor. With (less) weight now the screw has ample room to deflect down. Conceivable the screw will be 5/8" out of stud which will have a really big bearing on how much it would hold. – DMoore Feb 11 '15 at 7:50
1

How much load a screw can hold does not depend on its length, assuming it is long enough. Instead, the load is a function of its cross-sectional area. A typical range for proof strength for steel is 50 to 100 kpsi (i.e., a screw with a 1 square inch cross-sectional area of steel can hold up to 50,000 to 100,000 pounds).

See here and here.

Of course, as the diameter of your screw increases, the stud is likely to fail first.

  • 1
    Withdrawal loads are a function of screw diameter, penetration depth, and wood species. In addition the 50 kpsi etc. are ultimate strengths at which the steel undergoes non-elastic deformation. Working loads are a fraction of ultimate strength based on an appropriate factor of safety using sound engineering practice. – ben rudgers Jan 12 '15 at 1:53
  • Ben: Hence I mentioned the proof strength to avoid going beyond the yield point. My main point is to point out to the OP that the length of the screw does not really matter, as long as it's long enough. Look at the other answer -- "So now we have a whole one inch actually used for support. Enough to keep things tipping over but not enough to hold anything heavier than a picture up." As if doubling the length to 2 inches will increase the load the screw can hold. – wsw Jan 12 '15 at 2:51
  • @wsw the length of the screw does matter as there is typically going to be a 'pull' load in many case (if we're talking shelves supported by the wall, for instance) it's a load shared with the stud, of course. – DA01 Jan 12 '15 at 3:44
  • @DA01: I disagree and I don't follow your example. If we can agree that when a screw is tightened, it is stretched under tension. However, note that the threaded part is not stretched; hence doubling the length of the threaded part will not help increase the strength of the screw. – wsw Aug 25 '17 at 3:38
  • 2
    @wsw I see what you are getting at. Yes there is a limit to the screw strength. But that usually exceeds that of the pull out strength in shelving situations given the number of screws used. So typically the load it can hold is more dependent on threads and length. – DA01 Aug 25 '17 at 8:31
1

Assuming you mean a standard #8 wood screw, and a standard office, not much. A 2 inch drywall screw will hold even less.

The first half inch of most screws are tapered and thus don't add much to it's strength. Then you need to subtract the thickness of the bracket and the drywall. So now we have a whole one inch actually used for support. Enough to keep things tipping over but not enough to hold anything heavier than a picture up. And if you overtighten it into the wood it's more of a pin than a screw.

Offices often have commercial steel-stud walls. Bad news for you as steel studs are designed to hold up drywall and nothing else. They are thin sheet metal.

"Industrial-style shelving" implies industrial-style loads. Get a self-standing model from any shipping or warehouse supplier.

And the reason drywall screws hold less weight is because they are intended for one (and only one) purpose - holding drywall to steel studs. They are hard, thin, brittle and will snap off if overloaded.

  • Its a #12 wood screw 2in long. I drilled a pilot hole slightly smaller. I used 3/4 galvanized floor flanges to secure my galvanized pipe which is holding the shelf. There are two screws in each flange. Into wooden studs. 3 supports per shelf, so thats 6 screws. It doesn't need to hold much. Id say 50 to 100lbs would be more than enough – Stan Morris Jan 12 '15 at 16:56
  • Back them out and get some 4 inch #12 screws. Predrill deeper and set them properly (don't overtighten with a big drill) and you should be fine. (you are quite sure you hit the middle of the stud? 1/4 inch from the edge won't hold much) – paul Jan 16 '15 at 11:52

Not the answer you're looking for? Browse other questions tagged or ask your own question.