Wood is an excellent building material for the outdoors. Whether it is used for house siding, outdoor furniture, decks, fences, or outbuildings, wood holds up well against weathering, as long as it is maintained.
Whenever water and wood mix, there is the possibility of water stains. Applying oil- and water-based wood sealers in advance and regularly sealing the wood is the best way to avoid water staining. But well-intentioned routines often fall by the wayside or the wood may not have been sealed in the first place. Painting or staining the wood are two ways to cover the stains. But if you would rather restore the wood to its former natural beauty, the cure is a collection of approaches that you tailor to your specific wood and type of stain.
Unpainted wood may have been previously treated with wood preservatives. Newer wood preservatives, while toxic, are far less toxic than older wood preservatives. As all are fungicides and pesticides that may be harmful to your health, care should be taken when working with wood that you suspect may contain wood preservatives. Additionally, household bleach is moderately caustic and oxalic acid is highly caustic, so always wear safety protection when working with these materials.