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When a deck collapses, it's often because the ledger wasn't properly installed. Whether a collapse is the result of foolish work practices (say only nail-gunning a ledger to a band joist) or simply outdated technique (no flashing between the siding and the ledger — which is how we learned to do it years ago), or even a deck put to uses for which it wasn't designed, i.e., hot tubs, the thought of a deck coming down is terrifying.

And yet, there has been scant agreement until recently about best practices. But there's more at work here than just sticking on a board that stays. The ledger board is the control-point for layout, and where it's hung on the building affects the experience of using the deck. “It's not a lot of the deck,” says Dennis Schaeffer, owner of Creative Wood Products, a deck company in Fenton, Mich., “but it's the most important part of the deck.” Here's a quick guide to getting it right.

  • Making the connection. The American Wood Council's “Prescriptive Residential Deck Construction Guide” (www.awc.org) is a free resource outlining proven techniques. Although general, it does prescribe key details such as stripping the house siding before ledger installation, flashing above the ledger, and lag requirements.

Speaking of which, the Guide specifies ½ -by-6-inch lags. Although those work great — and are code in many parts of the country — the newer, faster-to-install screws such as those from Olympic Manufacturing Group (LedgerLok) or Simpson Strong-Tie are my preferred solution. Schaeffer advises drilling all the way through the brick into the open cavity space and attaching bolt to bolt. His view? That will soon be code.

As for flashing, I like P&G Solutions' DuraFlash. It's pre-bent and is easy to work with. Flashing above the ledger prevents moisture from corroding bolts or traveling along the bolt into the house, causing leakage.

  • Laying it out. Forget pulling strings for post layout. I use the ledger — already attached to the building — for layout. Basically, you mark the ledger and the cantilever beam, at the same time, for joists. Next, cut 1½ inches off each end of the ledger. Bolt it to the house. Cut each band joist to length; face nail it to the ledger. Once fastened (and supported temporarily at the opposite end) level and square the band joists in real time. And because you laid out the beam at the same time, joists run straight.
  • Locating the ledger. Before I set the ledger, I tuck a peel-and-stick membrane under the siding, extending it below the ledger so trapped water can escape. I caulk liberally under door thresholds. I then position the ledger so the decking, once installed, tucks under the home's entry door threshold. I think this makes a graceful transition onto the deck. Other builders drop the deck a few inches below the door to accommodate snow drifts, which is also nice.
  • Free-standing. Affixing a ledger is loads of work. Many deck builders skip it altogether and build free-standing decks.

—Mark Clement is a remodeler in Ambler, Pa., and a member of the DeckExpo Live Demonstration Team.