I’m building a dock that will be six feet wide, supported on cribs. I’m going to go out at least 50 feet, with a floating dock at the end. What width should I make the cribs under the dock? And how far apart should they be?
—Bob La Rose, via e-mail
Though the dimensions may depend on a few site-specific details, Garry Best, the owner of Garry Best and Sons Carpentry in Lake of Bays, Ont., says you’ll need four cribs, roughly 10 feet apart. “One at the shore, one at the end, and two evenly spaced in between.”
The cribs need to be as wide as the dock: six feet, in your case. Paul Bell, the owner of PBCarpentry in Lake of the Woods, Ont., says the simplest option is to make the cribs 6′ by 6′ (buy 12′ timbers and cut them in two). Ideally, for the most dock stability, you should make the width and length of the crib at least as large as its height.
The total size of your project may be restricted by local bylaws and other regulations, so if you haven’t done so yet, check with your building department to find out about size limitations. “It’s easier to design a crib dock to already fit within the township’s parameters,” explains Best.
Other limiting factors when it comes to cribs? The depth of your lake—crib docks aren’t practical in water deeper than eight feet (see the above width-length-height rule of thumb). They’re also not great on lakes with severe winter ice, wildly fluctuating water levels, or a very squishy bottom.
“A soft bottom is just not good footing for a crib, since it may lean or shift after it’s filled with rock,” says Bell. “And it will likely continue to sink year after year.”
Also, don’t forget about the aquatic creatures that these big honkin’ containers of rocks may disturb: According to Fisheries and Oceans Canada, crib docks are more environmentally disruptive than other docks because they can interfere with fish spawning habitats. So, no surprise: As you would with any project that requires work in or near water, you’ll need the proper permits and approvals from, potentially, several environmental bodies and levels of government. This doesn’t mean you can’t build the dock of your dreams, but if it involves cribs, you may have to deal with a little extra red tape.