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The Dock Primer

The Shape of Things to Come

The most common dock shape is the rectangle. It is, after all, the simplest and most economical shape to build. But often there are better choices, both from the shoreline's perspective and that of our cottage wish list. The neat thing is that most variations are based on the rectangle, often with one or more rectangular sections joined together to make a more stable, useful, and attractive dock.

In most cases, dock stability increases with size. It's simply a matter of percentages - the bigger the dock, the smaller the impact your visit, or nature's tantrums for that matter, will have on it. But it's also true that as dock size increases, so too does the risk of harming nature. All docks possess the potential to disrupt currents enough to erode submerged lands and shorelines (including those belonging to your neighbours), increase the shading of submerged lands, and disturb submerged lands via a dock's seemingly benign footprint, all of which can destroy aquatic flora and destroy fish habitat and spawning areas. Then there's the connection of dock to shoreline and dock to cottage, both of which are no slouches when it comes to disrupting that delicate ecological balance. The bigger the dock, the greater the potential for mayhem. "Bigger" also costs more to construct and maintain. So big docks are bad, right? Maybe. The problem is, build a dock too small and not only is stability compromised, it might also fail to serve your needs. That's why that map of your shoreline is so important - it makes it easier for both you and the various approval authorities to choose the dock best suited to both your shoreline and your needs.

The needs part of the equation is your wish list. The list tells you what activities are envisioned for the dock, and these often dictate minimum size requirements. For instance, while considered small craft, both sailboards and canoes can become serious dock hogs when out of water, demanding plenty of deck acreage to swing around and launch. And things only get worse should Aunt Mabel demand unobstructed sitting room for her and her favourite deck chair while all this is taking place. That said, if your shoreline includes a usable beach (check your map if you forgot), some things - such as swimming zones and sailboard storage, may be best assigned to the beach, reducing demands on dock size. However (dock planning has no shortage of "howevers"), if big boats are in the picture, there's little point in opting for a small dock. Should nature make waves, and the dock isn't up to snuff, it's goodbye to both dock and boat. If the shoreline has no usable beach - where water and land meet at a steep cliff, for example - the dock then takes on the role of a beach.

Dock Shapes

L-shape

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The Limits to Thin

With the exception of finger docks (we'll get to them later), 3' is the practical minimum width for any dock. You need that much room for two people to pass without risking one, or both, being bumped into the drink. Also, as you will see in our discussion of the various dock types, most docks have minimum size requirements and stability suffers if you try to go smaller.

If your needs are modest (perhaps in rare harmony with your budget), the basic rectangle may be your best option. However, by adding a second rectangular section perpendicular to the first dock (at the deep end), the resulting T-shape or L-shape adds to dock stability- like training wheels on a bicycle - and the shapes created help to define designated activity areas. For example, one end of a T-shape could be set aside for sunbathing, while splashing and diving are moved to the other end. The shapes can also "capture" protected areas of water for the mooring boats or to create a children's wading area.

Breaking away from the basic rectangle allows us to direct foot and boat traffic, and activity patterns, reducing dock congestion. Therefore, less deck acreage is required to accomplish the same goals. This means less cost, less impact on the environment, and usually makes for a more attractive shoreline. And, as a bonus, those additional rectangles can be added or subtracted over time as needs - and finances - change.

What shouldn't be considered for budgetary reasons are finger docks. Finger docks are long and skinny rectangles that run out from a much larger main dock or breakwall. They are designed to provide the maximum number of slips (stalls to moor a boat) in a given area, not to save on construction costs. Because of the reduced width (sometimes down to a foot), finger docks wiggle around just like fingers and provide wobbly access to boats, but not much else. If your activity list demands greater versatility, or you don't relish that impending doom feeling of a tippy dock, stay away from finger docks.

Between a Dock and a Hard Place

The main problem docks experience is one shared with everything else in the universe: entropy. Or the idea that nothing lasts forever. Wood, metal, plastic, concrete - all the basic ingredients of dock building - and even nature's own bedrock, are all under continual assault from two very destructive forces - stress and decay. The deleterious effects of stress (the result, say, of visiting boaters bashing into the dock, or nature hurling up huge waves, or spring ice pounding at your shoreline) can be reduced by distributing the loads. For a dock to survive to its maximum life expectancy, all loads must be shared by as much of the structure as possible. That's construction rule number one.

Decay is often a keen partner to stress when it comes to destruction. Wood rots, plastic degrades, concrete spalls and cracks, metal corrodes, rock erodes - it's all part of nature's regenerative process.

Generally, decay thrives in an environment of warmth, a little moisture, and a little oxygen, all readily available at your local shoreline. Too much or not enough of any of these ingredients and decay moderates its attack. The secret to longevity, therefore, is to take advantage of this weakness, using good design and appropriate materials to discourage the onset and growth of decay. That's construction rule number two.

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Dock materialism

Wood

Wood is the most common element in residential dock construction. It's relatively easy to work with, reasonably priced, and has some "give," allowing it to bend slightly under duress. It's also at its strongest under short-term loads (such as when your neighbour Phil clobbers the dock with his new ski boat), a decided advantage to waterfront structures. And things made of wood are usually easy to rebuild should nature prove the better of humanity once again.

On the other hand, wood is at its worst down at the waterfront - wet and fat one moment, dry and skinny the next. Therefore, joining pieces of wood in dock building requires different techniques than the accepted practices of house carpentry.

The preferred deck woods for dock building are western red cedar, redwood, cypress, and eastern white cedar (in that order), all of which offer reasonable longevity and beauty. For most docks, that's also the preferred structural list, but for dock cribs and permanent piles, stronger woods, such as Douglas fir, hemlock, and tamarack (in that order) are a better choice. Unfortunately, this group is not as resistant to rot as the first. For permanent piles, western larch, pine, and even spruce can be used if fir is not available.

The downside of opting for the preferred species, such as western red cedar, is cost. It may last longer than other species, but it's also becoming increasingly expensive. Granted, that could be said for all types of wood. Certainly, the better decking species, being naturally resistant to rot, will outlast species such as spruce, but what if the bank account won't accept that logic and demands a cheaper solution? That's when we compromise. One way to do this - already mentioned - is to reduce the deck acreage. Or we can try to extend the life of lesser grades of wood.

Unfortunately, the standard route to wood preservation - paint and stain - is not the answer for docks. Any coating you put on a dock will fade, blister, and peel. Not only will this look terrible, but damaged coatings also trap water, creating an ideal spot for a wood-destroying fungi family to take up housekeeping. So you can either scrape and re-coat the dock every few years or use preferred wood species and do as many dock builders advise - let the wood go naturally grey, an option that suits my minimal-work ethic just fine.

Pressure Treating

But we're not out of the protected woods yet. There's still pressure treated spruce or pine, that Kermit-green alternative seen on countless decks, jungle gyms, and suburban retaining walls. Pressure-treated pine or spruce is about 20-30% less expensive than the preferred decking species, such as cedar, but because the grades of lumber set aside for treatment are usually low, pressure-treated wood is typically more susceptible to warping and cracking when exposed to weather than the untreated decking species, and even some of the structural species, such as fir. Most of the problem wood is labelled S-GRN (the chemicals applied when the wood is wet with sap, and therefore not as absorbent); pressure-treated wood labelled S-DRY is typically of much better quality and longer lasting, but also more expensive.

Because it can leach chemicals into the environment, pressure-treated wood is banned for waterfront use in some areas and, in all cases, construction should take place well back from the shoreline, with the finished dock being left to thoroughly dry and "age" before being launched into the water. Working with pressure-treated wood is more difficult, the sawdust considered toxic, and each cut end must be sealed with an approved preservative, all of which exposes the builder (not to mention the flora and fauna living in the water) to some nasty chemicals.

A reasonable compromise is to use pressure-treated wood for the structure of the dock, keeping the preferred species for the decking, thereby lessening the odds of exposing skin to potentially harmful chemicals.

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Plastic

Plastic has become a common building material for docks. Compared to most woods, metals, or concrete, the types of plastic used in dock construction are relatively low in strength and lack hardness, which rules them out for structural duties. Plastic is, however, the primary material for dock floats and when supported by an appropriate structure - typically made from wood, metal, or concrete - plastic materials can be used for decking. Plastic is also waterproof and decay-resistant, a decided advantage when it comes to dock construction.

The cost of plastic decking usually fits somewhere between cedar and pressure-treated wood, although some variations are more expensive than even the preferred species of wood decking. Typically, plastic decking comes in traditional "planks" of solid polyethylene (PE), extrusions made from polyvinylchloride (PVC), and composites of recycled PE and wood by products. Unfortunately, all plastic decking has a propensity to sag, which means that decking cannot extend across the spans of traditional dock designs (check with the decking's manufacturer).

Plastic decking is more fragile than wood and more prone to splitting during installation (so follow the instructions), but when installed properly, it can certainly offer long life.

Hardware

I cannot stress enough the importance of good hardware in building docks. Dock hardware is that bewildering array of metal brackets (usually steel) used to brace corners and joints, connect dock and ramp sections, hold the legs of pipe docks in place, and basically add strength to any dock connection under load. Technically, it doesn't fasten stuff together; it leaves that task to the nails, screws, nuts, and bolts. Instead, once secured in place with nuts and bolts and the like, dock hardware shares and transfers loads, diminishing stress at crucial junctures. Joints that are nailed or screwed together without the benefit of dock hardware will inevitably pull apart.

It doesn’t make sense to waste your time and money on second-rate hardware - whether it’s your own creation (sorry), a piece of metal conscripted for a duty it wasn’t designed for (such as barn-door hinges used to join sections of dock), or even most hardware sold from mass-merchandising outlets. Whether you’re buying individual pieces or acquiring the hardware as part of a completed dock or in a kit, buy your hardware from an established dock builder. It’s an expense you’ll never regret.

As for fasteners, screws and bolts hold a dock together much better than nails. The extra cost is minimal, but the increase in strength is not.

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