Which construction material is primarily used for outdoor decks and railings?

Thermoplastic composite lumber is an excellent choice for outdoor decks and railings due to its durability and resistance to environmental factors. This material is made from a mix of wood fibers and plastic, providing the aesthetic appeal of wood while offering enhanced resistance to moisture, rot, and insects. Unlike traditional wood, thermoplastic composite lumber does not require regular sealing, staining, or painting, making it a low-maintenance option. It also has a longer lifespan, which is advantageous for outdoor applications where exposure to the elements is a significant concern.

Pressure-treated wood is another common material for outdoor decks and railings but does require maintenance and has limitations in durability compared to composite lumber. Concrete and metal may be used in specific applications but do not offer the same visual appeal or ease of installation typically associated with decks and railings. Therefore, thermoplastic composite lumber stands out as the best choice for these outdoor structures.