Build a top notch deck

Five strategies for DIY deck-building

By Steve Maxwell


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Durable decks are more difficult to build than they look. That's why it pays to take the time to incorporate top-notch construction details into your next deck project. They're going to cost you a little more time and money up front, which is why few deck-builders bother. But the fact is you can easily add 10 to 20 years of life to your structure if you do things right, all while enjoying a deck that looks better and is easier to maintain. Diligence is always a good design.

1. End-Spaced Deck Boards

End-spacing is a key water-control detail. Wherever floorboards touch each other end to end, you're sure to foster premature rot. What else would you expect when thirsty end-grain surfaces come together and hold water between them long after rains stop? The solution is to install deck boards so they meet only over double joists spaced about 1/2" apart. This detail allows the ends of neighbouring deck boards to be spaced apart between 1/8" to 3/16", with a free drainage zone underneath. By allowing vulnerable areas of the wood to dry quickly like this, rot doesn't have the same easy start.

There are two hassles to this system. Besides having to install two joists every so often instead of one, you're restricted in where you can locate deck-board joints. The best way around this problem is to predetermine deck- board lengths that allow joints to occur in sync with your double-joist locations.



TOP: 1/8" to 3/16" end space

SIDE: 1/2" joint space

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


3. Safe & Solid Railing Design

The most powerful railing design advantage begins with your deck's support posts, the ones that rest on the concrete piers. Instead of cutting them off at deck-floor level, extend the posts high enough to form the main uprights of your railing whenever you can. This takes a little more planning up front, but the result is a super-solid railing that never loosens.

The best design for your project depends on how high the deck floor is above surrounding soil. If it's low to the ground, then building codes typically don't require railings to meet safety parameters. (Double-check with your building inspector to determine what's right where you live.) In cases like these, the best railing designs include routed pockets in vertical railing posts that hold horizontal railing members. These look good, they don't interfere with snow removal and they're very easy to paint or stain.

If your deck is going to be high enough to require a railing for safety reasons, then consult your building inspector for the proper spacing and height required to stay out of trouble. You may also find that a removable railing design is worth thinking about. The ability to take sections of railing down for refinishing and repair is a valuable advantage.


- 36" to 42" top railing

- support post continues through to railing

- less than 4" openings between balusters

- less than 2" spacing below lower rail


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

5. Routed-Edge Details

If you have a router, you can improve the quality of your deck with tasteful details and transform it from something ordinary into something that makes people take notice. The secret is three different router bits that you may already have in your workshop.

If you can only afford to add one large deck-building router bit to your collection, let it be a 3/4" roundover. One pass along the top and bottom corners of the edge of standard 2-by construction lumber yields a perfect semicircular profile. This bullnose shape looks gorgeous along the front of stair treads or wherever deck boards overhang the sides of a deck. The operation takes just a few minutes, with results that are out of proportion to the effort invested.

Want even more style for your deck? Get yourself a 2 1/4" chamfering bit. You'll need at least a 12-amp router to spin this bit, but the results make big posts and railing parts look like a million bucks. Aim for a chamfer that's 1/2" to 3/4" across, started and stopped several inches from the ends of the deck components involved.

A tiny chamfer bit in a one-handed router transforms ordinary deck boards into something special. Cut a deck board to length, then route a 3/16" chamfer on all the upper edges of the wood before fastening it down. Repeat the process with each deck board as you complete the surface. The results look better than square-edge boards, and later they're also easier to coat properly with finish because of the chamfer.

Building your own deck offers advantages that go beyond just saving money. As a diligent DIY builder, you also enjoy the chance to incorporate high-quality details and features that few professionals can afford. Take your time, learn what good deck design is really all about, then put it into practice in your yard. The biggest problem you'll have is how to say “no” to all those neighbours who will want you to build a top-notch deck for them too.


- stop chamfer on posts

- micro-chamfer on deck-board edges

- bullnose profile on deck edges

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