Chris-
Yes I have used this technique for heavy loads (magnetic white boards), however there are few loads as heavy as a loaded book shelf.
I used to figure about 2 pounds per running inch of bookshelf when designing bookshelves.
How tall are the shelves? How close to the top edge would the strip be mounted? How deep (~10")?
So if your studs are 16" o/c that's 32lbs per shelf per stud.
If you're talking about a 4-shelf unit (~40 to 48" high & about 10" deep). The CG of your book load is about 6" off the wall, the total (per stud) book load is about 130 lbs.
If the line of action to resist the shelf pulling away from the wall is ~3" from the top & the bottom edge of the shelf bears against the wall you have a resisting "couple" of about ~36" minimum.
If my way of looking at it makes sense; we've got 6" x (130lbsof books
Or (torque yanking bookshelf off the wall) 930 in-lbs resisted by a
36" couple>>>>>
Need ~25lbs of safe allowable withdrawl per stud location. We also need 155lbs of safe allowable shear resistance per stud location.
I'm was concerned about shear loading than withdrawl but that's just my point of view.
I'm talking about burly #12 or #14 SMS not POS drywall screws. Should be able to get a lot more than 25lbs withdrawl safely out of a #12 unless your studs are paper thin.
btw any idea stud gage? anything less than 20 & I'd get worried.
Anybody willing to verify / correct my assumptions & calcs? The are just "seat of the pants" but they seem reasonable.
Chris, I guess we should also consider the "unanticipated" load, extra
125 lbs point load; painter using the shelf as a foot hold. I've done that dsort of "extra" loading.
You could whip up a small frame out of plywood, sawn lumber or MDF & do a quick experiment. Screw it the to wall with the bottom ~4" off the ground & then stand on it.
Or you could install a SMS thru a piece of 3/4" ply, leave the head proud & see if you can pry bar it out. Figure you mechanical advantage on the pry bar (10 or 12 to 1?)
One good test is worth 100 expert opinions. :)
cheers Bob