Water-Repellents and Preservatives

• Wood decks can be treated with a water-repellent and preservative alone. These provide some protection against the elements while allowing the natural beauty of the wood to show, but must be reapplied each year. Preservatives do not have the benefit of pigments, which means that the wood may be affected by the sun's rays.
  
  

Penetrating Stains

• Penetrating stains are absorbed into the wood's fibers, soaking the surface and filling the pores. These stains often contain water repellents such as wax as well as preservatives to protect your wood by limiting the growth of mildew and mold and repelling insects. Penetrating stains are best for weathered, rough or coarse-texture wood. If your deck is smooth, sand or wet the surface to open the pores so that it absorbs the stain. Stains require no surface preparation other than cleaning and are suitable for decks as well as siding, trim and fences.
  
  

Semi-Transparent or Solid

• Semi-transparent stains contain pigment,s and many also contain wood preservatives and water repellents, combining three products in one. Oil-based products penetrate the wood without forming a film so that the wood grain shows through. Latex semi-transparent stains are film-forming and do not penetrate the wood as a true stain. Using an oil-based semi-transparent stain ensures the wood can breathe, which prevents peeling and cracking when the moisture content in the wood is high. The pigment in the stain also aids in preventing UV damage. Solid-color stains are more like a thinned paint and require the application of primer before use. A solid color latex stain is preferable to oil-based. Solid-color stains of higher quality often contain a weather repellent or preservative as well.
  
  

Durability

• Water repellents, or sealers, typically protect your deck for about 6 to 12 months before a new coating must be applied. Preservatives, on the other hand, protect your deck for up to two years. If the preservative contains pigment, then you may find the deck only needs treatment every three years. Solid color and semi-transparent stains are very durable, as long as the wood isn't subjected to significant moisture. Depending on the quality of the stain, you may only have to restain your deck every three to seven years.