huangyhg

drywall screws
wood frame construction
an idiot contractor on one of my jobs started using 2 1/2" drywall screws instead of real nails for stud to plate connections and other connections. what equivalent penny size can this be? the box is marked "black coarse drywall screws". so not galvanized! is this contrary to the intl building code? what does coarse mean? could there also be a different shear stress, pullout strength, etc. between these screws and nails specifically called out by the ibc?
if your bottom plate is treated, then i would reject the non-galvanized screws. this is especially important as the new types of pressure treatment (non-cca types) are much higher in corrosiveness than the cca lumber previously used. reject it.
typically, wood screws do have higher capacities than nails, but with "drywall" screws i'm not sure.
since i wrote this thread i talked to the manufacturer.
they said the screw is #8, and coarse meaning as in fine or coarse threads.
diameter of #8 screw is 5/32 inch at shank and 7/64 inch at root , root governs.
7/64 inch = 0.1094 about 12 gauge which is 0.1046 and that puts it at or 6d (11.5 ga).
the length of a 6d is 2 inches
smaller than the 2.5 inches of the screw, so i think that 6d is about the answer.
any comments
agree with jae, about the steel corrosion with new pt products. this will be the next big contruction issue in a few years. even simpson literature recommends an access panel to check fastener performance with the new pt, unless sst is used,
the drywall screws are typically hardened steel. they are not appropriate in shear loading. i would consider requiring renailing with correct fasteners.
thanks boo1
on the steel corrossion, yes i know about that too, been to simpson seminar's also.
on the steel hardness factor, ok, the screw is no good for shear and too small.
pt999:
just curious, when you were talking to the manufacturer, did you happen to ask what the shear and pullout loads where? surely, they have test reports on their screws.
yes, i was curious about that too - but with "drywall" screws, would a manufacturer have tests performed to check for wood to wood shear? i wouldn't think so...but a check with the screw manufacturer would still be appropriate.
on test reports, i asked the mfg to send me their technical literature, but i am not really expecting anything really useful, just catalogs.
and my idiot contractor has a lot of screws to pull out. i think he has few loose screws too.
do you need to remove the screws in all locations? you could probably leave them in place to rust along side the new connectons without significant detrimental effect.
i would not remove the studs to re-nail. consider toe nailing the studs or cliping the studs in place. with the walls raised consider using simpson sp2 (bottom plate) and sp4 (top plate).

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