Along the Front Range, exterior surfaces take a beating that most of the country never sees. Intense high altitude UV bakes oil, grease and organic staining straight into concrete, hail leaves grit and debris ground into driveways and patios, and wildfire smoke haze settles a fine film of soot across decks, fences and walkways. Heavy pine needle drop and cottonwood fluff pack into deck boards and along fence lines, where they hold moisture and feed the black and green growth that makes concrete slick. Freeze thaw cycles work that trapped moisture deeper into the pores of the slab every winter, and by spring the road sand and magnesium chloride de icer tracked up the driveway has left a chalky white haze and a salty residue that quietly eats at the surface. Most homes in Parker, Denver, Aurora, Littleton, Highlands Ranch, Lakewood, Castle Rock, Centennial, Englewood and Greenwood Village do best with pressure washing once a year, usually in late spring once the de icer season is over, or ahead of a sale, a party or a fresh coat of sealer or stain.