Rough cut lumber can make for beautiful and durable outdoor projects, but it requires proper treatment and preparation first. Here is a comprehensive guide on how to treat and prepare rough cut lumber for optimal outdoor use.
Choose the Right Wood Species
Some wood species are naturally more rot and insect resistant than others. When using rough cut lumber outdoors, choose woods like cedar, redwood, cypress, or pressure-treated pine. These woods contain natural oils, resins, and properties that help protect against moisture, decay, and pests. Avoid using raw softwoods like fir or spruce outside.
Dry the Wood Properly
Freshly cut “green” wood needs time to dry out and acclimate before being used for projects. Stack rough cut lumber with spacers in between to allow air flow. Allow a minimum of 6 months up to 1 year of drying time depending on thickness. Use a moisture meter to test – lumber should read 15% moisture content or less before finishing and installing outside.
Mill and Plane Down
Once dry, running the boards through a thickness planer will smooth down rough surfaces and get rid of dried cracks or checking on the outer layers. Milling lumber to uniform dimensions makes it easier to work with for outdoor projects. Always mill to final dimensions after drying.
Choose an Effective Wood Sealer
Sealing untreated lumber is crucial for outdoor longevity. Penetrating sealers soak into the wood grain and protect against moisture and UV rays without hiding the natural grain. Consider oil-based finishes like tung or linseed oil, or water-based options like acrylic, varnish, or polyurethane.
Apply Weather Protective Finishes
Clear exterior wood finishes further prevent moisture penetration while allowing the wood’s natural color to show through. Spar urethane or marine varnish are good options. For added color without hiding grain, use semi-transparent exterior wood stains. Apply 2-3 coats as directed by manufacturer instructions for optimal protection.
Use Proper Outdoor Fasteners and Hardware
Use corrosion resistant screws, nails, and hardware for all outdoor projects made with rough cut lumber. Hot dipped galvanized or stainless steel hold up best to the elements. Pre-drill holes for screws to prevent splitting.
Allow Proper Drainage and Air Flow
Allow space between boards for drainage and air flow on structures like signs, benches, or raised beds. Avoid direct ground contact with concrete footings or joist hangers to prevent moisture wicking upwards into the wood.
Apply End Grain Sealant
Seal all exposed end grains thoroughly with a clear wood sealer. End grain absorbs more moisture and deteriorates faster. Apply 2-3 coats allowing drying between applications.
Maintain with Regular Upkeep
Periodically inspect outdoor wood projects for signs of damage, wear, cracking, or decay. Refinish or reseal as needed to maintain protective barriers against moisture and UV. Address any pest, fungal, or drainage issues right away.
Properly treating and preparing rough cut lumber is important for outdoor wood projects to last. Allowing adequate drying time, milling to uniform dimensions, using weather-resistant wood species, and applying protective finishes will help maximize durability and longevity of your next exterior woodworking project. With proper care, you can enjoy the beauty and versatility of rough cut lumber outdoors for years to come.
Frequently Asked Questions about Treating Rough Cut Lumber for Outdoor Use
What are the best wood species to use for outdoor projects?
The most weather-resistant species for outdoor use are cedar, redwood, cypress, pressure-treated pine, or composite lumber. These contain natural protective oils, resins, and properties.
How long does rough cut lumber need to dry before using?
Allow a minimum 6 months up to 1 year of drying time for rough cut lumber prior to use in outdoor projects. Thicker wood needs more time. Use a moisture meter to test moisture is 15% or less.
Should rough cut lumber be milled before or after drying?
Always mill lumber to final dimensions after the drying process is complete. Milling while still wet can restart drying cracks and checks on the surface.
How often should outdoor wood projects be refinished?
Inspect outdoor wood projects yearly and refinish as needed, usually every 2-4 years depending on weathering, use, and wood type. Address any visible damage right away.
What hardware should be used for outdoor wood projects?
Use corrosion resistant screws, nails, hinges, brackets, and hardware made from galvanized steel, stainless steel, or quality non-ferrous metals outside.
Should end grain be sealed on outdoor lumber?
Yes, always seal end grain thoroughly with 2-3 coats of clear wood sealer. End grain absorbs more moisture and will deteriorate faster when left unfinished.
How can proper drainage be allowed for in outdoor wood projects?
Leave space between boards, use joist hangers or footings to avoid direct ground contact, and ensure water can freely drain off and pass through.
Conclusion
Treating and properly preparing rough cut lumber is an important process to ensure outdoor wood projects stand the test of time. Allowing adequate drying time, milling to uniform thickness, selecting durable wood species, properly sealing and finishing all surfaces, using quality hardware, and addressing drainage considerations will protect your exterior woodworking projects from moisture, UV damage, pests, and decay. With the right wood preparation on the front end, you can enjoy creating beautiful and long-lasting outdoor structures using locally sourced rough cut lumber tailored exactly to your needs.