Choosing the right lumber is crucial for any successful outdoor project. The type of wood you select will impact everything from structural integrity and weather resistance to aesthetics and longevity. This comprehensive guide examines the pros and cons of various lumber options to determine what lumber should be used for different outdoor applications.
Introduction
When embarking on an outdoor project, whether building a deck, fence, pergola or raised garden bed, one of the first decisions that must be made is which type of lumber to use. There are many factors to consider when selecting wood for outdoor use including:
- Durability and rot/insect resistance
- Strength and load-bearing capabilities
- Aesthetic qualities like color and grain patterns
- Budget
- Availability and sustainability
The optimal wood choice depends largely on the specifics of your project such as location, exposure to weather, desired lifespan, and appearance. By understanding the properties of common lumber varieties used in outdoor settings, you can make an informed decision about which option makes the most sense for your needs.
This comprehensive guide examines the most popular types of lumber for outdoor use to help determine what lumber should be for your next project.
Cedar
Cedar is one of the best woods for exterior use thanks to its natural resistance to rot, insects, and weathering. This aromatic softwood has distinctive reddish-brown hues and a loosely grained texture. Cedar contains natural oils that act as preservatives to help the wood last longer.
Advantages
- Excellent rot and insect resistance
- Naturally weather-resistant
- Attractive appearance
- Available in a range of grades and price points
Disadvantages
- Lower structural strength than denser woods
- Requires pre-drilling for nails/screws
- Can be expensive depending on grade
Best for: decks, fences, outdoor furniture, raised beds, planter boxes, pergolas, trellises, siding
Pressure-Treated Pine
Pressure-treated pine is one of the most ubiquitous outdoor lumber options. Pine is an inexpensive, lightweight softwood that is treated with chemical preservatives to resist rot, fungi, and insects. This process forces protective chemicals like copper azole into the wood.
Advantages
- Treated to resist rot, decay, and insects
- Relatively inexpensive
- Widely available
- Can be used for structural applications
Disadvantages
- Not as naturally weather-resistant as cedar or redwood
- Can warp, twist, or bow over time
- Treatment chemicals may have an odor
Best for: Deck framing, posts, beams, fences, retaining walls
Redwood
Redwood is another rot-resistant softwood excellent for outdoor projects. It has a distinctive reddish-pink coloration and straight, even grain pattern. Redwood contains tannins and oils that act as natural preservatives.
Advantages
- Extremely decay and insect resistant
- Beautiful grain patterns
- Does not require chemical treatment
- Naturally stable with little expansion/contraction
Disadvantages
- More expensive than pressure-treated lumber
- Lower strength than some hardwoods
- Can be prone to checking/cracking
Best for: decks, outdoor furniture, planter boxes, raised garden beds, privacy screens, benches
Douglas Fir
Douglas fir is a very common and affordable softwood used for structural applications. While not as rot-resistant as cedar or redwood, it has good strength and workability. Douglas fir has a pale yellow-tan color with a straight, pronounced grain.
Advantages
- Good strength and stiffness
- Straight, even grain
- Affordable and readily available
- Easy to work with using tools
Disadvantages
- Not naturally rot-resistant
- Can warp or twist over time
- Susceptible to checking
- Needs protection from weather
Best for: Framing lumber, posts, beams, decking steps, railing caps, benches
Ipe
Ipe is an extremely dense, durable tropical hardwood that makes an excellent decking material. Though expensive, it provides unmatched longevity and performance. Ipe has a dark brown coloration and a tight, interlocking grain.
Advantages
- Extremely rot, insect, and UV resistant
- Dense and strong – lasts for decades
- Slip-resistant surface
- Attractive exotic look
Disadvantages
- Very expensive
- Can be very hard on tools
- Needs pre-drilling
- Difficult to find certified sustainable sources
Best for: Decking, outdoor furniture, docks, boardwalks
Composite Lumber
Composite lumber offers a rot-resistant, splinter-free alternative to wood. Composed of wood fibers bound with plastic resins, composite lumber has gained popularity for being durable and low-maintenance. The texture often mimics the look of real wood.
Advantages
- Won’t rot, crack, or splinter
- Resists insect damage
- No staining/sealing required
- Slip-resistant decking options
- Range of colors/textures
Disadvantages
- Can become hot in sunny weather
- Not as strong as most woods
- Contains some non-recyclable plastic resins
- Prone to mold/mildew in damp environments
Best for: Decking, rails, benches, outdoor furniture, raised beds
Tips for Choosing the Right Lumber
- Consider your project’s desired lifespan, exposure, and functionality to determine the required durability and performance. Prioritize rot-resistance and water-resistance for frequent wet conditions.
- Select appearance-grade lumber for visible uses like decking, fencing, and outdoor furniture. For structural framing, lower grades offer cost savings.
- Ensure the lumber is sustainably forested and harvested if possible. Look for FSC certification or reclaimed/recycled products.
- Choose wood appropriate for the spans, loads, and demands of the project. Use denser, higher-strength woods for critical structural elements.
- Allow for proper acclimatization and drying of lumber before use. Minimize warping and checking with proper storage techniques.
- Use compatible metals, fasteners, and hardware to avoid galvanic corrosion between dissimilar metals. Stainless steel and coated fasteners are recommended.
- Apply protective finishes to any wood without natural rot-resistance. Use paint, stains, oils, or water-repellent coatings properly suited for the wood type and environmental conditions.
- Inspect periodically for signs of wear, damage, rot, splitting, or excess weathering. Address issues quickly to prevent accelerated deterioration.
Best Practices for Outdoor Use
Proper practices during design, construction, and maintenance are key to getting optimal performance from your chosen lumber. Here are some top tips for success:
Design Elements
- Allow for adequate spacing between boards to enable drainage and air circulation. This helps minimize cupping, trapping moisture, and facilitating decay.
- Incorporate design features like overhangs and sloped tops to protect surfaces and redirect water runoff.
- Select boards with the recommended spacing for the span direction based on the wood type and dimensions. Consult structural design values.
- Stagger board ends in repeating patterns for a more pleasing, consistent aesthetic. Allow 1/8″ gaps between ends.
Construction Techniques
- Pre-drill all holes for screws and nails to avoid splitting, especially near board ends and edges. Countersink fasteners.
- Use exterior-rated, corrosion-resistant fasteners and hardware suited for the lumber type. Stainless steel and coated fasteners are ideal.
- Ensure proper joist spacing, beams sizes, footing depths, and structural bracing accoding to code requirements and manufacturer specifications. Don’t cut corners.
- Allow suitable acclimation time and check moisture content prior to construction. Dry, conditioned wood prevents issues down the road.
- Apply protective end sealer or primer to any fresh cut ends to prevent moisture wicking. Avoid exposing end grain when possible.
Maintenance Practices
- Inspect regularly for damage, wear, raised nails, rot, splitting and weathering. Make repairs immediately to avoid bigger problems.
- Clean surfaces periodically with soap and water. Avoid harsh cleaners or pressure washing.
- Sand or refinish weathered surfaces to restore appearance and protect the wood underneath. Spot treat any damaged areas.
- Reapply protective finishes like stains, paints, oils, and water repellents as needed to renew weather resistance. Follow manufacturer directions.
- Ensure proper drainage and ventilation around wood structures. Correct any standing water issues quickly.
Outdoor Projects and Recommended Lumber Types
The optimal lumber choice differs based on the specifics of each outdoor project. Some general recommendations:
Decks
Framing: Pressure-treated pine, redwood, cedar
Decking: Ipe, cedar, redwood, pressure-treated pine, composite
Railings/Trim: Cedar, redwood, pressure-treated pine
Fences
Posts/Rails: Pressure-treated pine posts, cedar rails
Slats/Boards: Cedar, redwood
Pergolas
Beams/Rafters: Cedar, redwood, pressure-treated pine
Trim/Slats: Cedar, redwood
Sheds
Framing: Pressure-treated pine, Douglas fir, cedar
Siding: Cedar, redwood
Planter Boxes
Walls: Cedar, redwood, composite
Raised Beds
Walls: Cedar, redwood, composite
Outdoor Furniture
Frames: Teak, eucalyptus, shorea
Slats: Cedar, redwood, teak
Frequently Asked Questions
What is the most rot resistant wood?
The most rot-resistant woods are cedar, redwood, and ipe. Their natural oils, tannins, and dense structure resist decay.
What is the strongest wood for outdoors?
Ipe is the strongest for decking. Douglas fir is very strong for structural framing. Oak is a great hardwood option.
Can pressure-treated wood be used for decking?
Yes, pressure-treated pine is frequently used for deck boards and railings. It requires protection from weathering.
Does cedar need to be sealed outside?
It’s recommended to seal and protect cedar outdoors with finish coats, even though it has good natural resistance.
What is better: cedar or pressure-treated?
Cedar is more attractive, naturally resistant to decay, and ideal for visible surfaces. Treated wood is cheaper and frequently used for structural framing.
How long does cedar decking last?
With proper installation and maintenance, cedar decking can last 15-25 years or longer. Higher grades tend to last longer.
How long does Ipe last outside?
One of the most durable woods, Ipe can last 40 years or longer for decking with proper maintenance. It holds up extremely well to weather, foot traffic and wear.
Is composite better than wood?
Composite requires less maintenance and won’t rot, split or warp. But wood has greater strength and is more eco-friendly. Personal preference matters most.
Conclusion
When selecting lumber for outdoor applications, consider the required structural properties, environmental resilience, longevity, and appearance characteristics for your particular project. Utilize wood types that are naturally durable or pressure-treated for rot resistance. Allow for proper spacing, drainage, and airflow during installation. Apply protective finishes and conduct routine maintenance to further extend the service life of your lumber. With careful selection and care, you can achieve beautiful, long-lasting outdoor projects using quality wood appropriate for the job.