In most of the country, pressure washing is about looks. Around Puget Sound it is about protection. Our long wet season grows moss and algae on nearly every outdoor surface, and those growths hold water in constant contact with roofing, siding, wood, and concrete.
Roofs take the worst of it. Moss creeps under the bottom edge of composition shingles and lifts them, which breaks the seal and lets water past. Left alone long enough, moss can take years off a roof that otherwise had plenty of life left in it. It needs to come off carefully, at low pressure — blasting a roof does more damage than the moss did.
Walkways, driveways, and patios grow a thin algae film that turns genuinely slick in the rain. This is the one we get emergency calls about, usually after somebody in the household slips. Concrete and pavers handle real pressure well, so this is a fast, dramatic improvement.
Siding, fences, and decks sit in the middle. They need enough pressure to lift the grime and streaking but not so much that water is driven behind boards or paint is stripped. Pre-treating first means the cleaning solution does the work instead of raw pressure.
For most homes here, a wash every one to two years keeps everything ahead of the growth. If it has been longer than that, the first wash makes a bigger difference than people expect.
Superlux Gardening & Landscaping pressure washes roofs, siding, decks, fences, patios, and driveways across Snohomish and north King County. Call (425) 212-0027 for a free estimate.