Commercial Building Inspector B2Footings and FoundationsEasy
A commercial building inspector is reviewing the details for a wood sill plate connection to a concrete foundation wall. The plans specify pressure-treated lumber for the sill plate. According to the 2021 IBC, what is the minimum nominal width required for a wood sill plate that is anchored to a concrete foundation wall?
- A2 inches
- B8 inches
- C4 inches
- D6 inches
Show answer & explanationAnswer & explanation
Correct answer: A. 2 inches
IBC Section 2304.3.1 specifies that wood sill plates shall be not less than 2-inch nominal thickness. While the question asks for nominal width, standard lumber dimensions mean a 2-inch nominal thickness corresponds to a 2-inch nominal width (e.g., 2x4, 2x6). The minimum structural requirement is for the 2-inch nominal thickness to provide adequate bearing and allow for proper anchor bolt placement.
Why the other options are wrong
- B. 8 inches nominal (e.g., 2x8) is larger than typically needed for just the sill plate minimum.
- C. 4 inches nominal is a common size (e.g., 2x4) but not the minimum required nominal width.
- D. 6 inches nominal (e.g., 2x6) is often used for wider walls but is not the minimum.
Sill Plate Nominal Width
The smallest acceptable nominal width for a wood sill plate anchored to a foundation wall.
- Provides a bearing surface for wall framing.
- Must be pressure-treated when in contact with concrete.
- Minimum width ensures adequate bearing and connection strength.
Memory trick: Smallest sill plate width is two, anchoring securely for me and you.