Phoenix mold risk by city
This dataset ranks the largest Phoenix-metro cities by housing age — a leading, federally documented predictor of water leaks, and so of mold. Older cities like Tempe and Phoenix have far more pre-1980 homes, with the aging plumbing and roofs that leak, than newer ones like Gilbert and Goodyear. Climate risk is roughly the same valley-wide, so housing age is what separates one city from the next.
The data
Median year built and the share of homes built before 1980, by city, from the U.S. Census. The "risk tier" is a relative, housing-age indicator — not a measurement of how many homes actually have mold.
| City | Median year built | Homes built before 1980 | Relative leak-risk tier |
|---|---|---|---|
| Tempe | 1983 | 42.9% | Higher |
| Phoenix | 1984 | 42.3% | Higher |
| Glendale | 1986 | 36.8% | Higher |
| Mesa | 1988 | 29.9% | Moderate |
| Scottsdale | 1990 | 29.3% | Moderate |
| Chandler | 1997 | 10% | Lower |
| Peoria | 1998 | 9.2% | Lower |
| Gilbert | 2002 | 4.4% | Lower |
| Goodyear | 2007 | 3.9% | Lower |
Source: U.S. Census Bureau, American Community Survey 2019–2023 5-year estimates (tables B25035 & B25034). Cities are the largest in the Phoenix metro; Surprise is omitted (ACS data was not retrievable at publication). Free to cite or republish with attribution (CC BY 4.0).
How we built this — and its limits
Three inputs, kept transparent so you can check the work:
- Housing age (varies by city). From the Census ACS, we pulled each city's median year built and the share of homes built before 1980. This is the only one of the three inputs that genuinely differs from city to city.
- The leak-by-age gradient (federal). The American Housing Survey found that Phoenix-metro homes built before 1980 report inside water leaks at roughly 8.8%, versus about 4.6% for homes built 2010 or later — close to a halving. Leaks are the main driver of household mold, which is why older stock carries more risk. More on that in our guide to older Phoenix homes and mold risk.
- Climate (metro-wide, constant). Monsoon intrusion (NWS: June 15 – September 30, ~2.43 in of rain) and peak AC-condensate season (late May – October, with July/August highs near 106 °F) apply across the whole valley. They raise everyone's risk, but they don't vary meaningfully by city or ZIP — so we deliberately did not assign different climate scores by location. See the seasonal picture in our 2026 Phoenix mold risk report.
What this is not. It is not a count of homes with mold, and it is not a prediction for any single house — a brand-new home with a burst supply line can flood just as badly as a 1970s one. It is a relative, housing-stock read on where leak-driven mold risk concentrates across the metro. The tiers are simple cutoffs on the pre-1980 share: Higher ≥ 35%, Moderate 15–35%, Lower under 15%.
What it means for your home
If you're in an older-stock city — Tempe, central Phoenix, Glendale — the odds that your home has decades-old plumbing and a roof that's weathered many monsoons are simply higher, so hidden leaks (and the mold they feed) are worth checking proactively, especially before and after monsoon season. If you're in Gilbert, Goodyear, or Chandler, your bigger risks are trapped construction moisture in the first few years and first-summer AC condensate rather than aging pipes. Either way, the fix is the same: find and stop the water. If you're not sure, a mold inspection is built to locate the moisture source.
This dataset is part of our free Phoenix mold data. For how we source and weigh figures like these, see our methodology and data & sources.
Worried about a leak you can't see?
Older Phoenix homes hide moisture behind walls and above ceilings. If something smells musty or you've had a leak, get a fast, free, no-obligation quote.