Residential Building Inspector B1Public Safety and Special ConstructionMedium
A homeowner is constructing a new deck that will be attached to the dwelling. The deck is designed to support a uniform live load of 40 psf. What is the minimum ground clearance required for untreated wood joists supporting the deck?
- A12 inches (305 mm) to exposed earth
- B24 inches (610 mm) to exposed earth
- C18 inches (457 mm) to exposed earth
- D6 inches (152 mm) to exposed earth
Show answer & explanationAnswer & explanation
Correct answer: A. 12 inches (305 mm) to exposed earth
Untreated wood joists supporting a deck must maintain a minimum clearance of 12 inches (305 mm) to exposed earth to prevent moisture-related damage and pest infestation. This clearance helps ensure the longevity and structural integrity of the deck.
Why the other options are wrong
- B. This exceeds the minimum requirement and is not specified for joists.
- C. This clearance is for girders or beams, not joists, when exposed to earth.
- D. This clearance is insufficient for untreated wood joists to exposed earth.
Deck Joist Ground Clearance
The minimum vertical distance between untreated wood joists and the exposed earth below a deck.
- Applies to untreated wood joists
- Minimum 12 inches (305 mm) to exposed earth
- Prevents moisture and pest issues
Memory trick: Keep wood dry, twelve inches high.