Commercial Building Inspector B2Roof Ceiling ConstructionMedium
An inspector is checking the installation of a new roof assembly on a Type III-B commercial building. The roof deck consists of 1-inch nominal tongue-and-groove wood boards. What is the minimum required nailing schedule for these boards to wood rafters or purlins, according to common practice and IBC-referenced standards?
- AThree 8d common nails per bearing
- BTwo 10d common nails per bearing
- CTwo 8d common nails per bearing
- DOne 8d common nail per bearing
Show answer & explanationAnswer & explanation
Correct answer: C. Two 8d common nails per bearing
For 1-inch nominal tongue-and-groove wood boards used as roof decking, common practice and prescriptive requirements (often found in the WFCM or NDS, which are referenced by the IBC) typically call for two 8d common nails at each bearing (rafter or purlin). This ensures adequate fastening for shear and uplift resistance.
Why the other options are wrong
- A. Three nails per bearing is excessive for 1-inch nominal decking and not typically required.
- B. Two 10d nails would be stronger but are typically not required for 1-inch nominal decking and might risk splitting the wood.
- D. One nail per bearing is generally insufficient for structural roof decking.
Wood Decking Nailing Schedule
The specified pattern and size of fasteners (nails) required to attach wood roof decking to its supporting members (rafters or purlins) to ensure structural integrity.
- Critical for resisting gravity loads, wind uplift, and diaphragm shear.
- Varies based on decking thickness, material, and span.
- Governed by prescriptive tables in wood design standards (e.g., WFCM) referenced by IBC.
Memory trick: Nailing wood decks takes two nails to hold tight.