SMART INSPECTOR SCIENCE
CANTILEVERED DECK ISSUES
A “CANTILEVERED” DECK OR BALCONY IS HUNG ON THE SIDE OF A BUILDING WITH NO SUPPORT POSTS. TYPICALLY, THE HOME’S FRAMING JOISTS ARE EXTENDED BEYOND THE ENVELOPE TO SUPPORT THE DECK. DECK FLASHING DONE RIGHT Here’s what to look for with deck flashing (Illustration X039). Deck boards must be spaced to allow drainage near the wall. Flashing above the deck must originate behind the siding and extend to allow drainage over or around the deck boards. Also, two-part flashing must be placed around the joist and lapped over the moisture-resistant wall covering below.
Note that the structural deck joist is an extension of the home’s wood joist framing. This is common in residential construction.
Photo 1. Cantilevered deck.
Illustration X039 Cantilevered Deck Flashing.
A REAL-LIFE EXAMPLE
From above, the deck shown in Photo 1 looks fine—or at least the fresh paint and caulk look good. But maybe the paint is a clue that someone’s trying to hide something. As we look for deck flashing near the rule, we can’t see any flashing through the caulk (Photo 2), but we can see a deck board tucked into/under siding and pitched into siding (the ruler shows the pitch discrepancy). The deck board directs water into the wall and over the top of painted brick veneer. 20
ASHI Reporter • MAY 2021
Photo 2. Deck flashing.
