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.

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.

Photo 1. Cantilevered deck.

Photo 2. Deck flashing.

Tom Feiza has been a professional home inspector since 1992 and has a degree in engineering. Through HowToOperateYourHome.com (htoyh.com), he provides high-quality marketing materials that help professional home inspectors educate their customers. Copyright © 2021 by Tom Feiza, Mr. Fix-It, Inc. Reproduced with permission.

By Tom Feiza, Mr. Fix-It, Inc. HowToOperateYourHome.com

FRAMING CONCERNS

Sistered joists are visible beneath this deck (Photo 3), but the sisters are not supported at the ends and provide no structural support. Maybe they’re just a fresh nailing surface.

Photo 3. Sistered joists.

Viewing from the opposite direction confirms our suspicion: improperly sistered joists (Photo 4). There’s a new corner support post, but no structural beam over the post. We can also see more clearly that the deck board actually extends over the top of brick veneer, allowing water to drain into the wall. Luckily, the deck is protected by a wide overhang so water exposure is limited, but I would still check the brick veneer and the home’s interior for water intrusion damage.

THE TAKEAWAY

Cantilevered decks and balconies always raise concerns regarding improper flashing and control of water. You must watch for serious rot, water intrusion and structural issues. Always identify these and consider recommending further evaluation.

TO LEARN MORE, ATTEND TOM’S TECHNICAL PRESENTATIONS AT EDUCATIONAL SESSIONS FOR ASHI CHAPTERS.

Tom can also provide his knowledge for your educational event; contact him at Tom@HTOYH.com.

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