Residential Building Inspector B1Roof-Ceiling ConstructionHard
A residential building inspector is evaluating the roof framing of a new home. The rafters are spaced 24 inches on center and span 12 feet. The ceiling joists are also spaced 24 inches on center and are nailed to the sides of the rafters. What is the minimum number of 10d common nails required for each rafter-to-ceiling joist connection to act as a rafter tie?
- A5 nails
- B4 nails
- C3 nails
- D2 nails
Show answer & explanationAnswer & explanation
Correct answer: C. 3 nails
According to IRC Table R802.5.1(1) or R802.5.1(3) (Fastening Schedule), a rafter-to-ceiling joist connection requires a minimum of three 10d common nails when the ceiling joists serve as rafter ties. This ensures adequate resistance to rafter thrust.
Why the other options are wrong
- A. 5 nails is more than the minimum required by code.
- B. 4 nails would provide additional strength but is not the minimum required.
- D. 2 nails is typically too few for a critical structural connection like a rafter tie.
Rafter-to-Ceiling Joist Fastening
The connection method and number of fasteners required between a rafter and a ceiling joist when the joist functions as a rafter tie, resisting outward thrust.
- Crucial for preventing rafter spread and wall collapse.
- Specific nail size and quantity are code-mandated.
- IRC Table R802.5.1(1) provides fastening schedules.
Memory trick: Rafters push, ties hold fast; three nails keep the house from falling.