Prepping a deck is crucial for getting the most out of the deck stain. Regardless of the type or quality of deck stain, you are using it will not perform as expected if the deck is not prepped correctly. Deck stain needs to be applied to a clean, dry and bare wood surface in order to provide a long-lasting protective barrier against foot traffic and harsh elements.
When dirt is present in the wood pores the stain cannot penetrate like it needs to. This can lead to stain drying on top of the surface resulting in a shiny or blotchy finish as well as premature failure. Mold and mildew that are not cleaned prior to staining will continue to infiltrate the wood underneath the stain. This can lead to wood rot and decay. Fungal growth will also attack the stain causing a darkening appearance.
Maintaining a wood deck will ensure you get the longest lifespan and most use out of the extra outdoor living space. To maintain the appearance of a deck it should be cleaned and recoated every couple of years on average.