Build a top notch deck

Five strategies for DIY deck-building

By Steve Maxwell

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2. Concrete Pier Foundations

Since decks seem so simple, it’s easy to underestimate the need for a solid foundation. Easy at first, anyway. But it only takes a bit of frost heave or settling to make even the fanciest decks tilt and sag. That’s why it’s wise to look beyond standard deck-block foundations. Sure, they’re cheap and easy, and they might do OK on solid, well-drained soils. But how do you know until you’ve invested all that time and money into your new deck? Why risk thousands of dollars to save hundreds?

The best deck foundations are poured into heavy cardboard pier tubes that extend down below the frost line. U-shaped, galvanized-metal fittings called “post saddles” anchor the wooden deck posts to the concrete piers in the tubes. The piers themselves should also include a piece of 1/2″ rebar in the centre, extending up to within 4″ of the top. Distance between piers depends entirely on your deck design, as does pier diameter. Although 6″-diameter piers offer plenty of support for almost any deck, there’s another issue to consider. Long decks benefit from larger-diameter piers because they’re easier to work with. As you’ll discover when digging holes for the cardboard forms, it’s not easy to bore a straight line of holes. Rocks and variations in soil consistency can cause your auger to move out of alignment. Bigger piers provide a larger target for aligning all the post saddles.


– optional anchor bolts (for roof support)

– rebar extends down length of concrete pier

– galvanized post saddle

– black poly prevents frost heaving


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