Home/King County, WA
Washington -- population 2,268,178

King County, WA Property Research

Real data from four public sources, not an internal estimate: the EPA's radon zone classification, Census housing-age records, FEMA's natural hazard risk index, and NOAA's recorded storm history for this county. Every figure below links to where it actually comes from.

Hazard Summary

King County, WA hazard summary: FEMA National Risk Index rated Very High; EPA radon zone 3 of 3; most frequently recorded hazard is heavy rain (8 events, 2015-2024).

Radon Risk

Zone 3 -- low potential. EPA predicts an average indoor radon screening level below 2 pCi/L for this county.

This is a county-wide prediction from geology and soil data, not a measurement of any specific home -- EPA recommends testing every home regardless of zone. See our guide on negotiating radon mitigation after inspection.

Source: EPA Map of Radon Zones

Housing Age

King County has 988,330 housing units. About 34% were built in 1969 or earlier -- old enough that knob-and-tube wiring, lead-based paint, and galvanized supply lines are all realistic possibilities worth checking for, not just a general inspection line item.

2020 or later
11,640
2010-2019
132,922
2000-2009
131,770
1990-1999
116,987
1980-1989
134,529
1970-1979
121,181
1960-1969
109,851
1950-1959
74,261
1940-1949
46,054
1939 or earlier
109,135

Does knob-and-tube wiring have to be replaced before closing?

Source: U.S. Census Bureau, ACS 5-Year Estimates, Table B25034

Natural Hazard Risk

FEMA rates King County's overall natural hazard risk as Very High, relative to the rest of the country.

EarthquakeVery High
Inland FloodingVery High
AvalancheVery High
LandslideRelatively High
Heat WaveRelatively High
Source: FEMA National Risk Index

Recorded Storm History (2015-2024)

NOAA recorded 11 storm events in King County between 2015 and 2024. This is actual event history, not a risk model -- the counts below are individually logged storms, not a prediction.

Heavy Rain
8
Lightning
1
Debris Flow
1
Flood
1
Source: NOAA National Centers for Environmental Information, Storm Events Database

Guides Relevant to This County's Housing Stock

Does a Standard Home Inspection Check for Asbestos?Can Cast Iron Sewer Pipes Fail a Standard Home Inspection?What Is a Federal Pacific Stab-Lok Panel and Why Inspectors Flag It?Do Federal Pacific (FPE) Panels Affect Insurance Like Zinsco Panels?Will a Zinsco Panel Fail a 4-Point Inspection?How to Spot Polybutylene Pipes Before Buying a House

Get Your Free Property Report

BeforeRegret pulls live seismic hazard data, validates the address, and builds era- and county-specific inspection priorities and seller questions into one report -- with anything not yet independently verified clearly labeled, not guessed at.

Get Your First Report Free

This page reports what these four public agencies have published for King County as a whole -- it is not an assessment of any specific address or property, and does not replace a licensed home inspection, radon test, or insurance review for a specific home. Data last checked August 10, 2026.