Build a better boathouse

“You have to expect repairs at some point in the future,” Smith adds. “The less you start with, the less it will eventually cost.” He encourages the structure to be as open and as minimal as possible, to allow shoreline currents to flow, to let sunlight reach the bottom and to allow the free movement of fish. As well, you should use staving–the planking that skirts the dock–only where needed. The purpose of staving is to prevent a boat from getting under the dock and to hold boat bumpers that protect the hull. Otherwise, staving is largely cosmetic. Its overuse has a severe impact on the aquatic environment and impedes the movement of fish and wildlife. Where staving is necessary, provide adequate spacing for water flow and light penetration. Better yet, use horizontal boards where wider spacing is more practical. Staving should not extend below the high-water line.

The traditional crib for docks and boathouses is a timber frame of squared lumber, with alternating rows overlapping at the corners. Heavy, threaded galvanized rod runs vertically through holes bored in the ends of each timber. Broad galvanized washers at the top and bottom keep the nuts from burying themselves in the wood. Corrosion accelerates the decay of the timber; therefore, using galvanized hardware resists corrosion for longer.

The layered timber frame leaves open every other space on each side of the crib. This arrangement provides two features: an inside surface that allows the rock fill to grip and weight the crib and pore space for small fish and organisms to find refuge. Some builders will bolt a layer of heavy, corrugated galvanized-metal sheeting to the bottom of the crib, to help keep the structure from sinking into sand or other substrate. Metal sheeting also provides a platform for the inevitable rebuilding in the future, possibly 20 to 30 years down the road. Creating a crib with a false bottom provides refuge and shelter space as the rock fill stays above the bottom of the water. This feature helps to reduce habitat loss.

Smith suggests using woods such as cedar or hemlock in construction, rather than pressure-treated material. The former have natural preservatives throughout the timber, and if they can be purchased locally, you will help the regional economy. As it is a violation of the Fisheries Act to remove stone from the lake or river bottom to use as fill for the crib, bring in clean stone native to the area. Use large rock pieces to leave larger interstitial space as habitat and refuge. Do not use concrete or cement pieces as fill–these deteriorate into a smothering sediment.

Some marine contractors have turned to steel cylinders for cribs. These may prove to have a longer life-span than timber; however, the cylinders must have holes cut into them to provide space for shelter and refuge. While some property owners may be able to handle smaller wooden cribs, steel structures most likely mean bringing in the pros.