Redwood is an expensive building material and for good reason: the wood is naturally waterproof. Untreated redwood structures can last up to 30 years before succumbing to water damage. Still, some maintenance considerations are worth noting in order to extend the life of your deck or other outdoor structure.
Life Expectancy and Grades
Not all redwood is water-resistant. When choosing redwood timber for your outdoor project, assess the wood's color and grade. Deep red timber is the highest grade and the most water-resistant. Lighter-colored wood, from younger trees, is less water-resistant and will need to be treated to prevent water damage. Look for high-grade heartwood if you are interested in the most water-resistant construction material.
Stains
Deep red redwoods will lose their color if left untreated. Applying a clear finish to freshly cut wood will help retain the wood's appearance but will have no effect on its water resistance. Lighter redwood timber should be sealed with an oil-based stain. Oil-based stains seep into wood and provide a better water-wicking seal than surface treatments.
Construction
Because of redwood's expense, many home owners use redwood sparingly. The material is found most frequently in railings and decking -- highly visible areas with exposure to elements. Because redwood is a soft wood, take care not to use excessive nails or construction materials when fitting the timber into place.