CSLB General Building (B)Framing and CarpentryEasy
A contractor is evaluating the use of different types of wood screws for attaching subfloor to joists. Which type of screw is generally NOT recommended or permitted for structural subfloor attachment in typical residential construction due to its brittle nature and tendency to shear under stress?
- AStructural wood screws
- BSelf-tapping construction screws
- CDrywall screws
- DDeck screws
Show answer & explanationAnswer & explanation
Correct answer: C. Drywall screws
Drywall screws are designed for fastening drywall to studs and are made of hardened, brittle steel. They have a fine thread and a sharp point suitable for gypsum board, but they are not designed to withstand the shear and withdrawal forces common in subfloor applications and can easily snap.
Why the other options are wrong
- A. Structural wood screws are engineered for high strength and are an excellent choice for subfloor attachment, often replacing nails.
- B. Self-tapping construction screws are commonly used and accepted for subfloor attachment due to their strength and ease of installation.
- D. Deck screws are suitable for exterior wood applications and can be used for subfloor, though construction screws are often preferred.
Fastener Suitability for Subfloor
Selecting the correct fasteners (nails or screws) for subfloor attachment is critical for structural integrity, preventing squeaks, and meeting code requirements.
- Drywall screws are unsuitable due to brittleness.
- Common nails (8d or 10d) or structural wood screws are typically required.
- Fasteners resist uplift, shear, and squeaks.
Memory trick: Nails or structural screws, never drywall's blues.