Design & DIY

Expert advice for building a deck

Rob Dearing, general contractor in Gore Bay, Ont., since 1995: “There’s no point going in-between: You either build your deck on top of the soil or go all the way below the frost line with a foundation.” We asked Dearing for more deck-building tips.Reinforce the base: 
Always put 1/2″ rebar in concrete support piers—four vertical pieces tied into a cage, lowered into a 10″ or 12″ Sonotube before you pour the concrete. Smaller piers can support a deck, but the rocks and pockets of hard soil that you’re bound to hit will make it impossible to put the piers exactly where you need them. Oversized ones give you wiggle room to correct when you put posts and beams in place. I’m also sold on Bigfoot footing forms: They boost load-bearing capacity by creating a bell-shaped concrete bottom under the tubes.unnamedShear strength: 
Whenever a fastener has a load coming from the side, it’s under shear forces. A beam fastened to the side of a post—that’s a shear situation, and Code demands metal hangers and hanger nails, or bolts, but never screws. Screws shear easily; use them alone and your deck stands a good chance of falling down. Shear forces are strong on joists too; nails alone aren’t good enough. Use them to hold the parts up initially, then add joist hangers before the deck boards go down.Beef up the posts: 
Fork out the extra cash for 6×6 support posts. Even when 4x4s are actually strong enough, they don’t look it. And don’t stop your posts at floor level—extend them all the way to the top of the railing. The world already has too many wobbly deck railings.High impact, low effort: 
This is my signature design detail: I trim all the overhanging deck boards—after they’re installed—with a 15º bevel using a circular saw. I snap a chalk line as a guide, and just run the saw along the edge. You can clamp 
a 2×4 to run your saw against if you’re new at this. It’s fast and easy, and an angled edge looks way better than a square one.Flash it right: 
You’ve got to waterproof the seam between the building wall and the ledger board. But I see it done wrong all the time: Aluminum flashing corrodes quickly if it touches pressure-treated lumber—it’s a chemical thing. Prevent metal-to-wood contact with a layer of tarpaper. Better yet, use stainless steel flashing. Need some inspiration for your next outdoor project? Check out a full episode of Decks, Docks and Gazebos below!