King County asks more of siding than almost anywhere in the country. Between Puget Sound and the Cascade foothills, a house might absorb three feet of rain a year, months of gray damp that never lets walls fully dry, moss and algae on every shaded north face, and then a July heat spike that bakes the same boards it soaked all winter. Alpine Exteriors has been residing homes in this climate for 25 years, and the pattern is consistent from the Sound-side neighborhoods to the plateau communities out toward the foothills: siding here fails from moisture first and everything else second.
The King County Housing Stock Tells You Where to Look
So much of the county was built in the same few decades — split-levels and ramblers from the 1960s and 70s, then waves of 1980s two-stories — and those eras leaned hard on materials that have not aged well in our weather. T1-11 plywood panels wick water at every bottom edge. Early hardboard and composite lap products from the 80s and 90s swell, cup, and crumble once their coating fails. Even good cedar, the classic Northwest cladding, suffers when decades of deferred painting let the rain in.
The tell-tale signs are the same everywhere we inspect: paint that will not hold along the lower courses, dark staining under window corners, siding that sounds papery when you tap it, and — the one homeowners feel before they see — a musty smell in rooms behind a chronically wet wall. By the time siding looks bad in this climate, the sheathing behind it is often already involved.