Building functional, durable outdoor structures like decks, pergolas and sheds requires using the right materials. The components exposed to the elements day after day must stand up to rain, sun, snow, and seasonal temperature swings.
Selecting Appropriate Lumber
The framing and surface boards are critical structural elements. For decking, redwood, cedar, pressure-treated pine, and tropical hardwoods have natural weather resistance. Choose knot-free, straight boards without cupping, twisting or checks. Avoid lumber with excess knots, which create weak points more vulnerable to rot and insect damage. Hardwoods like Ipe are extremely durable but require pre-drilling to prevent cracking and splintering when fastening.
For structural framing, pressure-treated lumber is inexpensive and handles moisture well. Look for the PT stamp and end tags noting the exact preservative chemical used, either alkaline copper quaternary (ACQ) or micronized copper quaternary (MCQ). Verify the treatment meets standards for your projected use. Outdoor wood glues and protective end caps deter rot at cut points. Naturally decay-resistant cedar and redwood are pricier but long-lasting options. Redwood contains tannins that resist insect damage.
Picking Reliable Hardware
The nails, screws, hinges, joist hangers and brackets used outdoors must resist corrosion. Hot-dipped galvanized and stainless steel hardware is recommended for coastal and severe environments. The galvanization zinc coating deters rusting. Look for G185 coating (1.85 oz zinc/square foot) for optimal corrosion protection. Electroplated galvanized has a thinner coating. Stainless steel contains nickel, chromium and sometimes molybdenum to prevent oxidation.
For treated lumber, use hardware meeting ASTM standards like ACQ or MCQ for chemical compatibility. The metals cannot react adversely with preserved wood fibers and leach out corrosive oxides. Double hot-dipped galvanized or marine grade stainless hardware provides extra insurance. When assembling, pre-drilling prevents wood splitting while allowing seasonal movement. Waterproof polyurethane or epoxy wood glues also strengthen mechanical connections.
Choosing Durable Fasteners
Nails and screws penetrate and hold wood fibers, so durability against moisture and the elements is critical. For framing, choose 10 or 12 penny hot-dipped galvanized nails over thinner electroplated. The larger diameter nails have higher shear strength without bending. Ring shank and spiral shank nails have enhanced holding power due to greater surface contact. Combining water-resistant adhesives along with mechanically fastening joints prevents loosening over seasons.
Resistant to withdrawal forces, #8 and #10 trim or composite deck screws with ceramic, electroplated zinc or other protective coatings are ideal for decking and outdoor structures assembly, according to the experts at SPAX. The threads grip wood fibers to resist pull-out. Pre-drilling dense cedar or hardwood reduces mushrooming of screw heads. Setting nail heads and countersinking deck screws allows for flush finishes.
Finishing Right for the Elements
Clear wood sealants protect outdoor projects while allowing the natural grain to show. Oil-based penetrating finishes like tung oil deeply saturate pores but require maintenance as they fade, erode and leach over time. Water-based acrylics form a protective coating while still allowing proper moisture vapor release. Only use a finish compatible with any pre-treatments already applied to the wood.
Pigmented, film-forming stains add opaque, translucent, or semi-transparent layers of color. Prime all sides and cut ends thoroughly before installation, then apply two final finish coats for full protection on upper surfaces. Penetrating oil finishes need reapplication every one to two years. Inspect for wear, cracking or thinning and refinish as needed to prevent deterioration, swelling and rot.
Choosing suitable lumber, hardware, fasteners, and finishes ensures your outdoor structures can handle sun, rain, snow, and heavy use for years to come. Do your homework during the planning and design phase so material selection stands up to the conditions. Your properly constructed outdoor project will not only look great, but also provide lasting performance and enjoyment.