Mold guide from iLikeTo Fix

Mold problems find the moisture first

Musty smells, black staining, crawlspaces, and when remediation is oversold. Mold is always a moisture problem first. Find the source, size the job honestly, and know when it needs a pro.

39 mold problems, each named by the symptom you see

Sorted by the decade your house was built

Checks to run yourself and what fair repair costs look like

Find your problem Checks to run first

39 problemsEvery mold problem we cover, on this page

4 house erasPre-1940, 1940–80, 1980–2000 and since 2000

Checks firstWhat to rule out before anyone comes out

Fair costsWhat the work costs, and what not to pay for

1Find your problem

Start with the decade your house was built. The same symptom has different causes in a 1930s house and a 2010s one, so each era lists the mold problems that concentrate there.

Before about 1940 1940 to 1980 1980 to 2000 Since 2000 Any age

Homes built before about 1940

Galvanized supply, cast iron drains, cloth-wrapped wiring, ungrounded circuits.

All mold in homes built before about 1940

Musty smell with nothing visible Crawlspace with bare soil Growth returning after cleaning Black staining behind furniture on an exterior wall Testing offered before any inspection Old flood line on basement or cellar walls Plaster bubbling near a chimney No bathroom exhaust fan Insurance denying the claim

Homes built roughly 1940 to 1980

Copper supply, aging cast iron stacks, 60 to 100 amp panels, first-generation central air.

All mold in homes built 1940 to 1980

Growth around supply registers Damp along the bottom of a slab wall Bathroom fan venting into the attic Humidity above sixty percent indoors Water heater or AC pan with standing water Carpet that stayed wet Contractor quoting whole-house remediation from a photo Discoloration on the ceiling under a bathroom Crawlspace vents open year-round

Homes built roughly 1980 to 2000

Polybutylene and aluminum wiring, 150 amp panels, R-22 systems.

All mold in homes built 1980 to 2000

Vapor barrier on the wrong side of the wall Growth in a rarely used bathroom Window condensation running onto the sill Attic sheathing dark on the north slope Air sampling recommended before repairs Wet insulation in a wall cavity HVAC running with growth in the ducts Sump or drainage discharging next to the foundation Growth after a roof leak was repaired

Homes built since 2000

PEX on slab, 200 amp service, builder-grade equipment failing street by street.

All mold in homes built since 2000

Tight envelope with no mechanical ventilation Condensation on new windows Growth in a new-build closet on an exterior wall Bath fan running but not moving air Slab moisture under new flooring Humidifier set high in winter Warranty period still open Landscaping grading water toward the house Mold found during a home inspection

Any age of home

Problems that turn up whatever the decade.

Sustained summer humidity Storm-driven water intrusion Low humidity and a persistent problem

2Checks to run first

Work through these in order before you book anyone. They cost little or nothing and often find the answer.

Find the moisture sourceA leak, condensation, high humidity or water coming up from the ground. Without fixing it, mold comes back.
Measure indoor humidityA cheap hygrometer will do. Aim to keep it below about 50 percent, and below 60 at most.
Size the area honestlySmall patches on hard surfaces are usually a cleaning job. Large areas, hidden growth and porous materials are not.
Clean small areas the right wayDetergent and water on hard surfaces, dried fully. Porous materials like carpet and ceiling tile that stay moldy usually need to go.

3What mold work costs

The short answerAccess drives the number more than materials do. Every problem page gives a range for judging a quote, and the cost guide lists the mold work you should not be paying for at all.

Read Mold cost: what to expect and what to skip before you compare quotes. A quote that cannot explain what it includes, or that fixes the visible symptom while leaving the cause behind, is the one to question.

4When to call a mold remediation pro

Read the page for your problem first. It says whether this is a job for a pro, and what a fair price looks like before you make the call.

Speak to a local mold remediation pro

Calls connect to an independent local contractor. How this works.

5Questions

Is black mold more dangerous than other mold?

Color does not tell you the species or the risk. Any mold growing indoors should be cleaned up and the moisture source fixed.

Do I need mold testing?

Usually not. If you can see or smell mold, you already know it is there; the job is finding the moisture and removing the growth. Testing before anyone has inspected is often a sales step.

Can I remove mold myself?

Small areas on hard surfaces, yes, with gloves, eye protection and good ventilation. Large areas, growth inside walls or ducts, and anything after contaminated water should go to a pro.

Why does mold keep coming back after cleaning?

Because the moisture is still there. Fix the leak, improve ventilation or lower the humidity, and the growth stops returning.

Written by Jaylan Jones. iLikeTo Fix earns a referral fee when a call connects to a contractor. See our business-model disclosure.

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