On fences, sealers will show wear in about 2 years and will need to be re-sealed in 3. Stain will show wear in about 4 years and need maintenance in 5. On decks, vertical surfaces will wear the same as fences, while the horizontal surfaces (floor, handrails, stairs) will last 1-2 years with either stain…
When using the correct PSI (Pounds per Square Inch) the wood should not be damaged. Correct cleaning and powerwashing is recommended by all stain manufacturers before application of their products.
With proper chemicals and professional cleaning, and power-washing, the grey can be removed and the wood will look like new after a good stain and seal.
The discoloration is a deterioration of the wood as a result of a combination of dirt, bacteria, decay, and fading from the sun.