Landscape timbers are a specialized type of treated wood product engineered for outdoor, non-structural applications in gardening and landscape design. They offer a cost-effective and flexible material for homeowners seeking to define areas, create contained planting spaces, or add a rustic aesthetic to their yard. These timbers are distinct from standard dimensional lumber due to their unique physical shape and the lower-grade wood used in their construction. Their primary purpose is to provide a durable, rot-resistant wood that can withstand prolonged exposure to soil and moisture without the higher cost of structural-grade wood.
Composition and Physical Characteristics
Landscape timbers are sourced from lower-grade wood species like Hemlock, Hem Fir, or Douglas Fir, which are not naturally resistant to decay. Their characteristic shape—typically having two rounded sides and two flat sides—results from their origin as “peeler cores,” the cylindrical by-product left after a log is peeled for veneer or plywood production. The flat surfaces allow the timbers to be easily stacked and secured together during installation.
To protect against moisture and insects, landscape timbers undergo pressure treatment where a water-borne chemical preservative is forced deep into the wood fibers. Modern residential products primarily use copper-based compounds such as Alkaline Copper Quaternary (ACQ) or Copper Azole (CA). These replaced older treatments like Chromated Copper Arsenate (CCA), making ACQ and CA a safer choice for consumer applications, including those near food gardens. Because the wood used is often dense heartwood, it absorbs less preservative than other lumber, potentially resulting in a shorter lifespan compared to fully-treated dimensional wood. Properly treated landscape timbers typically last between 5 and 20 years, depending on ground contact and environmental conditions.
Typical Uses in Landscaping Projects
Landscape timbers are highly versatile and are used in projects requiring delineation and containment rather than heavy load-bearing strength. A common application is creating borders or edging to separate lawns from flower beds, paths, or driveways. This helps prevent soil erosion and gives the landscape a clean, defined look.
Timbers are also a popular choice for constructing low raised garden beds and decorative flower boxes. Their ability to stack easily makes them ideal for building small retaining walls up to a few courses high. They can also be used to construct simple, non-structural elements like small steps on a gentle slope or sandbox borders. Due to their shape and lack of structural rating, these timbers are not suitable for constructing tall or load-bearing retaining walls.
Timbers Versus Standard Lumber and Alternatives
Landscape timbers are often compared to standard dimensional lumber, such as pressure-treated 4x4s or 6x6s. The primary advantage of landscape timbers is their cost-effectiveness, as they are significantly cheaper than precision-cut dimensional lumber. This lower price is due to their origin as a lumber mill by-product and their irregular, rounded shape. Standard dimensional lumber, conversely, is graded and structurally rated, making it the better choice for projects requiring verified strength and stability, such as decks or engineered retaining walls.
Alternatives to Wood Timbers
Alternative materials offer different trade-offs. Materials like stone, concrete blocks, or brick are more expensive and less flexible to install, but they offer superior longevity and a different aesthetic. Recycled plastic timbers are a viable alternative that requires no chemical treatment and can last for decades, often exceeding the lifespan of treated wood. However, these synthetic options often lack the natural look and feel of wood. Ultimately, the decision depends on whether the project prioritizes budget and a natural look (landscape timbers) or structural integrity and longevity (dimensional lumber or alternatives).