Mold Inspection DIY Guide

Room-by-room checklist to find hidden mold in your home

How to Use This

How to Use This: Walk through each room with this checklist and a flashlight. Start with bathrooms and basements — these are where mold grows most often. Check off each item as you inspect it.

Start Here

Start Here: Buy a hygrometer ($10-15 at any hardware store) and check your home's humidity. If it's consistently above 50%, focus on reducing moisture before inspecting for mold.

Ideal Humidity

30-50% (buy a hygrometer, $10-15)

Mold Growth Threshold

Above 60% humidity for 48+ hours

Bathroom

Check caulking around tub/shower for black or pink discoloration

Inspect under sink (look behind pipes at drywall)

Check ceiling above shower for bubbling paint or staining

Pull back shower curtain/door track and inspect

Smell test: musty odor = mold even if you can't see it

Verify exhaust fan works (hold tissue to vent — it should stick)

Kitchen

Check under sink for leaks or water damage

Pull out refrigerator and inspect wall/floor behind it

Check dishwasher door gasket and drain area

Inspect window sills for condensation damage

Basement

Look for white mineral deposits on walls (efflorescence = water intrusion)

Check corners where walls meet floor for discoloration

Inspect stored items (cardboard boxes, clothing) for musty smell

Check sump pump area and floor drain

Attic

Inspect roof sheathing (underside of roof) for dark staining

Check around roof penetrations (vents, chimney)

Look for daylight coming through (indicates gaps where moisture enters)

Verify bathroom exhaust vents to outside, not into attic

Bedrooms

Check window frames and sills for condensation or mold

Pull furniture away from exterior walls and inspect

Check closets (especially exterior wall closets) for musty smell

Inspect mattress underside if on floor or low platform

HVAC System

Remove a supply vent cover and look inside ductwork with a flashlight

Check around AC unit for standing water or staining

Inspect air handler drip pan and condensate drain line

Note when filter was last changed (every 90 days max)

Important

If you find mold covering more than 10 sq ft, or if it's in HVAC ducts, hire a professional remediation company (not just a handyman). DIY cleanup of large mold areas can spread spores throughout the house. Do NOT use bleach on porous materials — it doesn't kill mold roots in drywall or wood.

Important

If anyone in your family has unexplained respiratory symptoms, chronic fatigue, or recurring sinus infections, consult a healthcare provider about possible mold exposure. Some individuals are genetically more susceptible to mold illness.

Next Steps

Next Steps: If you found problem areas, address moisture sources first (fix leaks, improve ventilation, run a dehumidifier). Then review the Air Purifier Comparison Chart to add HEPA filtration in affected rooms.