How common is mold in Indianapolis homes?

Some mold is in every house

Start with what’s normal. Mold spores are part of outdoor air in Indianapolis, as they are everywhere, and they come inside on shoes, pets, clothes and every open door. A lab will find some spores in any house it tests. That alone isn’t a problem, and it’s why an honest answer to “how common is mold” has to separate spores drifting through from mold actually growing on something in the house.

Growth is what counts, and there’s no public survey that tells us what share of Indianapolis homes have it. What we can say is that the ingredients mold needs, moisture and something to feed on, are easy to come by here. Mold problems in Indianapolis homes are common, not rare, and many of them go unnoticed for a long time.

Why the Indianapolis climate sets the table

Central Indiana gets four real seasons, and each one delivers water in a different way. Spring brings long stretches of rain on ground that’s often still saturated from snowmelt, which tests sump pumps and gutters. Summer is hot and humid, and that damp air finds every cool surface in a basement or crawlspace. Winter is cold enough that warm indoor air condenses on windows and in attics, and the thermometer crosses freezing often enough to produce ice dams on many roofs.

The landscape adds to it. The city sits on fairly flat ground crossed by the White River, Fall Creek, Eagle Creek, Pogue’s Run and many smaller streams, and a lot of the soil around it drains slowly. Heavy storms can overwhelm storm drains quickly. None of this is unusual for the Midwest, but it means an Indianapolis house has to keep water out in every season.

The housing stock does the rest

Indianapolis has a wide range of houses, and nearly every type has a weak spot. Older homes in neighborhoods near downtown often have stone or brick foundations and little moisture control. Postwar ranches frequently sit over crawlspaces with thin or missing vapor barriers. Suburban homes across Marion, Hamilton and Hendricks counties often have finished basements, where drywall and carpet sit against a foundation wall that stays cool all summer. Newer homes are built tighter, which saves energy but can trap moisture when ventilation falls behind. We look at the age question in more depth in whether older Indianapolis homes are more prone to mold.

Where it usually hides

In our experience, the places people see mold are rarely the whole story. The usual spots in an Indianapolis house:

• The back side of finished basement walls, especially along the bottom few inches.
• Crawlspace joists and subfloor, fed by humid summer air through the vents.
• Attic roof sheathing, from winter condensation and bath fans that vent into the attic.
• Under sinks, behind toilets and around tubs, where slow leaks go unnoticed.
• HVAC equipment and ducts, particularly when the furnace sits in a damp basement or crawlspace.

A musty smell with no visible growth usually means one of those places. Our page on having mold without seeing it explains how inspectors find it.

Common doesn’t mean you should live with it

Because mold problems are common here, it’s easy to shrug them off. A few signs are worth acting on: a smell that returns every summer, humidity readings that stay above 60 percent, staining at the base of walls or on ceilings, and any leak or flood that wasn’t fully dried. Keeping an Indiana home at the right humidity prevents a lot of it. When the signs are already there, testing indoor air against an outdoor sample shows whether mold is growing inside or you’re just seeing the normal background.

We remove mold and mycotoxins from buildings. We don’t diagnose or treat medical conditions. If you have symptoms, please work with a doctor. With your permission, we’re glad to share test results with them.