Regarding wall anchor specifications

Question

Wall anchors say that they are rated for x number of pounds.

My questions are:

Is that “per anchor”? And, if so, how accurate is it? And up to what point?

For example: if I had 100 wall anchors rated for 100 lbs in drywall, and I distributed them evenly over a large space on my wall, could I hang a car? Doesn’t seem likely, but I don’t know.

Practically, I’m hanging shelves, and I may be placing some heavy stuff on them. I want to know how much weight I can with certainty say they can hold, given that I’m using less than the calculated weight limit for the anchors for drywall.

In short, is there a weight at which anchor specifications become unreliable? And if so, approximately what is it?

Answer 1

Yes, per anchor unless otherwise specified (and sometimes it is, e.g. in pairs).

Accurate? This is advertising we're talking about, and assumes perfect conditions. I'd halve the number given.

Regarding your car example, obviously at some point the load will overcome either the structural integrity of the entire drywall sheet (as opposed to the local structure immediately around the anchor) or the holding power of the sheet's fasteners.

Hollow wall anchors should be used as a last resort and with a grain of salt. Use common sense, and never use them for things that move. Since shelves don't move, but the contents do, I'd not rely heavily on anchors except in rare cases where studs aren't available for one part of the shelf.

Answer 2

Theoretically yes they’d support a car, but in reality no because of rotation (eccentric load).

To answer your question, the loads for fasteners are with a “safety factor” usually 0.6 times “ultimate load”...but understand it’s usually just in shear, withdrawal, etc. as per listing. So, if you’re asking it to do more (like keep a car from rotating off the support, not just shear support) then it could fail.