Residential Building Inspector B1Floor ConstructionMedium
A floor system utilizes a combination of 2x10 wood joists and 3/4-inch plywood subflooring. To prevent squeaks and improve the composite action between the subfloor and joists, what adhesive application is typically required by code, in addition to fasteners?
- ANo adhesive is required if the subfloor is adequately nailed or screwed.
- BA continuous bead of construction adhesive on the top edge of all joists.
- CA vapor-retarding adhesive applied over the entire surface of the subfloor.
- DAdhesive applied only at the ends of the subfloor panels.
Show answer & explanationAnswer & explanation
Correct answer: B. A continuous bead of construction adhesive on the top edge of all joists.
IRC R503.2.3 specifies that subfloor panels shall be fastened to joists with fasteners and a continuous bead of approved construction adhesive on all supporting members. This creates a stronger, more rigid bond, reducing movement that causes squeaks and enhancing the load-carrying capacity through composite action.
Why the other options are wrong
- A. While fasteners are essential, adhesive is commonly required by code for subfloor installations to prevent squeaks and enhance performance.
- C. Vapor retarders are separate components and not typically an adhesive type for subfloor-to-joist bonding.
- D. Adhesive is required along all supporting joists, not just panel ends, for effective composite action.
Subfloor Adhesive Application
The method of applying construction adhesive between subfloor panels and floor joists to enhance structural integrity, reduce squeaks, and improve composite action.
- Required by IRC (R503.2.3) in addition to fasteners.
- Applied as a continuous bead on all supporting joists.
- Reduces squeaks by preventing movement between subfloor and joists.
Memory trick: Fasten Firmly, Adhere Actively, Resist Rattles.