Will Redwood Rot?
Redwood is a frequent choice for the construction of decks, patios, fencing and outdoor furniture. Not only is redwood beautiful, it is also highly resistant to insects, mold and rot. Which is not to say redwood will never rot — it is, after all, an organic substance.
But by taking some simple precautions with your redwood furnishings and outdoor construction, you can keep them sound and looking great for years to come.
Redwood trees are divided into three genera. Metasequoia is a deciduous tree that grows only in one valley of China. Sierra redwood (Sequoiadendron gigantea) is an evergreen that native to western slopes of California's Sierra Nevada Mountains. Coast redwood (Sequoia sempervirens) is an evergreen that grows in the coastal mountains of southern Oregon and Northern California. Coast redwoods are huge, growing up to 350 feet tall and 25 feet in diameter over the course of about 1,000 years. Redwood has a layer of bark on the outside that can be up to a foot thick. Under the bark is the soft, light yellow sapwood. Under the sapwood, which can be several inches thick, is the heartwood, which is the red color from which the tree gets its name. Exposing the heartwood to sunlight, even for a brief period of time, causes the red color to darken. It is the heartwood that is rot and insect resistant.
Advantages of Redwood
Materials are available for outdoor construction, including pressure-treated lumber, plastics, composites and naturally water and insect resistant woods such as redwood, cypress and cedar. Redwood is a good choice for outdoor projects because it is not as resistant as pressure-treated lumber but it does not contain the wood preservatives that can cause harm to human health and the environment that pressure-treated wood does. Plastics and composites can be virtually impervious to rot and insects, but they do not have the same ability to fit into the natural outdoor environment and they are usually more difficult to work with.
Redwood can be painted, stained, polyurethaned or shellacked, or left bare. Penetrating oil stains and spirit stains as well as acid or chemical water stains works well. Left unfinished, exterior redwood tends to darken from exposure to sunlight, then it weathers to a soft driftwood gray color.
Water-damaged redwood is prone to rot, which can create unsafe structures that must be replaced. The best way to prevent water damage is to keep water from pooling on your deck or patio, direct rainwater away from the deck or stairs, and remove debris that could trap moisture on the surface of the redwood. Places where water is likely to pool are the little reservoirs created by nailheads that are sunk below the surface of a plank, ledgers where the deck connects to the house, the flat tops of the beams that support the deck or stairs, and handrail connectors. These areas should be inspected regularly for dry rot so they can be repaired before the entire structure is compromised.