Hey Kev - I was going to ask someone more in-the-know than myself if sheetrock (especially if glued in addition to screws) would provide some shear value. My buddy's brother (professional foreman, previously professional sheetrock hanger) helped me sheetrock my barn rec room and said it would add "a lot" of strength, but I never dug in deeper to find out what that means exactly. Is there a rule of thumb? Is it 50% of plywood shear? More or less?
It helps somewhat against racking once it is all up, but it does not provide "a lot" of strength. There were test done on framed houses with sheetrock walls, and the final conclusion was that sheetrock is not to be classified as to adding shear strength to a wall. But a lot of those test were conducted in California because of all of the seismic activity.
Does it add strength to prevent racking? It all depends on what one person calls racking vs. what another calls racking. It will never be as strong as OSB or plywood. But if you have a 16', 2x4 wall, and push on one end or the other, the wall WILL rack. Once you have 4 sheets of 1/2" drywall on it, then you go to one end or the other and push the wall, it will not rack unless you put a lot of effort into it. It would also be dependent on how it is fastened. Drywall nails will cut through drywall if you try to rack a wall, so one could say that drywall has no shear strength at all. using screws will reduce that somewhat, and naturally, if it is GLUED and screwed, then it is stronger yet. Exactly how much though is dependent on a lot of factors, and would really need quite a few of CONTROLLED test. Nailed or screwed, nailed and glued, screwed and glued, brand of glue, type of wood the drywall is on (Older fuzzy Oak studs, vs. new 2x4's), thickness of drywall, drywall mounted vertically vs. horizontally, then com[paring the vertical vs horizontal with nail, nails and glue, and on, and on, and on.
They do make a high strength drywall, and IIRC, it has fiberglass in it. I don't know whether it's in the paper or the Gypsum itself. There is a lot of variables as to what the shear strength actually is, and even climate would affect it which would also depend on how tight a house is.
Myself, I would say that it definitely does add shear strength to a wall, but ideally, OSB or Plywood would would be way better. Then of course there is the great debate that pops up every once in awhile about drywall vs. OSB
Myself, i like drywall on a garage. I don't throw wrenches, I don't run into my walls, and as far as strength, whether the garage is strong or not.......well, it's just as strong as my house with drywall inside. So as far as shear strength, I imagine that will be a new topic that will pop up on Garage Journal every once in a while. My take of it is that if the structure has good bones, then put on the walls what you want on the walls. But if you don't have good bones, then drywall will not be a sure fire cure.
