Build a top notch deck

Five strategies for DIY deck-building

By Steve Maxwell

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4. Non-Laminated Support Beams

No matter how good a deck looks when new, the real test is how it stands up structurally over the next two or three or four decades. And even if you choose rot-resistant materials such as cedar or pressure-treated lumber, that’s not enough to guarantee long life. Under conditions often found in conventional decks, rot can overtake key structural areas in 20 years or less. And this is especially unfortunate since it’s so easy to postpone rot with diligent design. This makes at least as much difference as the type of wood you choose.

You need an arrangement of deck parts that minimizes large wood-to-wood contact areas between pieces of lumber. And the biggest rot zone of this kind is the ubiquitous laminated beam. It’s certainly easier to spike together three or four 2x8s or 2x10s to get the support beams you need, but one-piece beams are better because water can’t seep in between the layers. This is key.

Pressure-treated 6x6s or 8x8s are your best bet for deck beams. They’re widely available, and the advantage goes beyond just rot resistance. If you need bigger beams, pressure-treated 6x12s and 8x12s are available as special-order items. Regardless of the shape, large timbers such as these also allow you to create the kind of decorative details on beam ends and edges that can vault your work beyond the ordinary. At a minimum, trim the ends at a 45º angle. For the investment of a few more minutes of work with a router, chamfered edges make any deck beam look terrific. Even if you only see the ends peeking out from under the deck, the results are worth it.


– solid beam prevents water retention

– angled and chamfered beam end

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