Drywall Screws

Types of Drywall Screws

There are two main types of drywall screws:

• Coarse-thread screws
  Best for wood studs. The wider threads grip wood tightly and reduce the chance of the screw pulling out.
• Fine-thread screws
  Designed for metal studs. The finer threads cut into metal more easily and provide a strong hold.

Drywall screws are also available in different lengths, depending on drywall thickness and framing type. Bugle head screws are designed specifically for drywall applications. The head has a flat surface top with a smooth concave progression from a head's upper perimeter to the shank in a shape similar to the bell of a bugle which smoothly countersinks into drywall preventing surface damage (paper tearing). It creates a flush finish without predrilling the countersink hole. It disperses stress evenly for better holding power. Also, most drywall screws are coated to resist rust, helping prevent stains from appearing on finished walls.

Proper Use

For best results, drywall screws should be spaced evenly and driven just below the surface of the drywall—snug, but not over-driven. Proper installation helps prevent cracking, popping, or loose panels over time.

The Ontario Building Code | Spacing of Screws

9.29.5.9. Spacing of Screws

(1) For single-layer application on a ceiling, screws shall be spaced not more than 300 mm o.c. on ceiling supports.

(2) Where the ceiling sheets are supported by the wall sheets around the perimeter of the ceiling, this support may be considered as equivalent to screwing at this location.

(3) Except as required by Sentence (4), for single-layer application on walls, screws shall be spaced,

(a) not more than 300 mm o.c. on vertical wall supports where the supports are more than 406 mm o.c., or

(b) not more than 400 mm o.c. on vertical wall supports where the supports are not more than 406 mm o.c.

(4) Except as permitted by Sentence (5), for single-layer application on walls, where gypsum board is required to provide bracing, lateral support or fire protection, screws shall be spaced not more than 300 mm o.c. on,

(a) vertical wall supports, and

(b) top and bottom plates.

(5) Where a fire-resistance rating is determined based on Table 1 of MMAH Supplementary Standard SB-3, "Fire and Sound Resistance of building Assemblies", Sentence (4) need not apply for the purpose of fire protection.

(6) Screws shall be located not less than 10 mm from the side or edge of the board.

(7) Screws shall be driven so that the heads do not puncture the paper.

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Performance Values

Fasteners performance values requirements depend on application. Use drywall screws for drywall application only.

There are several performance factors to be considered:

• Fastener shear strength: When applied at a 90 degrees angle, the measure of force required to break a screw.
• Connection shear strength: When a screw is connection two pieces of material, the force required to pull one piece in one direction and the other piece in the opposite direction until the connection fails (until the screw breaks or pulls out of or through either piece of material).
• Fastener tensile strength: The amount of force required to break (pull apart) a screw when pulling one end in one direction and the other end in the opposite direction, or when securing one end and pulling on the other end.
• Connection Tensile (Tension) Strength: When a screw is connecting two pieces of material, the force required to pull the two pieces apart by applying the force from between the two pieces outward in opposite directions until the screw head pulls through one piece or the screw threads pull out of the other piece (typically, the latter occurs first).
• Torsional Strength: The measure of the ability of a screw to withstand a twisting load to the point of breaking (typically measured in kg-cm or lb.-in.).

Drywall screws are excellent at what they’re designed for—attaching drywall. For anything else, always use the correct fastener (wood screws, structural screws, lag bolts, or rated metal fasteners). Using the right screw ensures strength, safety, and code compliance.

Drywall screws are designed specifically for fastening drywall to wood or metal framing, and using them for other applications can cause problems. Here’s why they should be used only for drywall work:

• They are brittle, not structural: Drywall screws are hardened so they drive easily, but that hardness makes them brittle. Under bending, shear, or vibration loads, they can snap instead of flex, which makes them unsafe for framing, shelving, or load-bearing uses.

• Poor shear strength: Drywall screws are designed to resist pull-out, not sideways (shear) forces. In applications like decks, cabinets, or general carpentry, shear loads are common—conditions where drywall screws can fail.

• Not rated or approved for structural use: Drywall screws do not meet building code requirements for structural fastening. Using them where structural fasteners are required can lead to inspection failures and potential liability issues.

• Corrosion limitations: Standard drywall screws have a phosphate coating, which is meant for indoor drywall environments. Outside drywall use—especially in damp areas—this coating offers poor corrosion resistance, leading to rust and weakened fasteners.

• Thread design is application-specific: Their thread and shank are optimized to hold gypsum board without tearing the paper face. This design is not ideal for wood-to-wood or heavy metal connections, where proper wood screws or self-drilling metal screws perform better.

• Safety and durability concerns: Because they can break without warning, drywall screws used improperly can cause sudden failures, leading to property damage or injury.

Drywall screws may seem like a small detail, but they play a major role in the strength and appearance of finished walls and ceilings. Using the correct type and installing them properly helps ensure a clean, durable result. Always use appropriate tools, personal protective equipment (gloves, glasses) to prevent injury.

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Source: https://grabber-construction-products.dcatalog.com/r/Grabber-Construction-Products/, the Ontario Building Code

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