What is Marine Lumber?
The conditions that lumber is continually exposed to in marine applications causes premature deterioration of the wood. To prevent deterioration and fight the effects of salt, wind, rain, sun and water lumber manufacturers provide products that have been specially treated to repel these weathering agents.
There are three general categories of marine lumber:
- Commercial grade marine lumber includes pilings and lumber that has been treated with creosote to withstand the harshest of marine conditions. Creosote is not approved for residential, personal or agricultural use because of the toxicity of the chemical. However, it does make wood very resistant to salt water. As preservation products improve, there are continually more techniques available for preserving marine lumber. Chromated copper arsenate, CCA, is also used to preserve pilings. Polymer coated pilings are available from some suppliers.
- Marine plywood is manufactured using waterproof glue and special techniques that eliminate the possibility of air pockets within the layers, or veneers, of wood. The veneers are pressed together with the grain of each layer oriented in a different direction from the previous layer. This creates a piece of plywood that is strong and flexible. Flexibility is essential when building a boat so as to create the curves necessary for an efficient hull. Marine plywood is usually made of woods that naturally contain oils, such as spruce, teak and Douglas fir.
- Decorative woods are used in marine applications for boat trim, molding, decking, louvered doors, handholds, and so on. The most common wood for decorative applications is teak. It is durable, light and has the natural oils necessary to repel moisture. Spruce, Douglas fir and other hardwoods also contain natural oils and are used in marine applications. The key to maintaining decorative hardwoods is to seal or oil them regularly.
For docks and similar structures the marine lumber of choice varies by personal preference. Due to human exposure, creosote treated lumber is not available for docks. Regular pressure treated lumber available from any lumberyard or home improvement retailer and will work fine. Cedar, cypress and composite lumber products are also widely used in dock construction.