Drywall screws are used in conjunction with nails and construction glue to fasten a piece of drywall across existing framework. The exact number of screws used in any given sheet of drywall varies from carpenter to carpenter and even from job site to job site, but there are screws of different sizes that may be called upon, depending on the exact situation
Drywall screws are manufactured in various sizes to better accommodate each individual job. Screws that measure 1-1/4 inch in length are appropriate for sheets of drywall that are 3/8, 1/2 or 5/8 of an inch thick, while screws that measure 1-3/8 inches are meant for sheets of drywall up to ¾ of an inch thick. Drywall sheets of a larger thickness, such as 7/8, 1 inch or 1-1/4 inch, require a screw length of 1-1/2, 1-5/8 or 2 inches respectively.
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Coarse vs. Fine Thread
Black drywall screws feature a coarse thread that is better suited for attaching drywall to wood. Silver screws are typically manufactured with a fine thread, which lends itself better to metal framework. Both types are made in different lengths to accommodate the various thicknesses of drywall board.
Additional Drywall Layers
Additional layers of drywall can be installed on top of each other to boost insulation, soundproofing and fire rating. In this case, a screw size of 1-1/4 inch can be used for installing the base layer while a screw size of 1-7/8 inch is required for the second and any additional layers.
Drywall screws aren't inserted by hand. Instead, professional drywall installers use a screw gun -- powered by either the electricity in a home or rechargeable battery -- to insert screws in a fast, safe and efficient manner. Some screw guns are equipped with a self-loading mechanism. This uses a plastic ribbon of screws that are automatically fed onto the tip of the screw gun, thus saving the drywall installers the hassle of having to retrieve a new screw each time.