Mold
I found mold — how much is too much to handle myself?
The short answer: a small surface patch of mold on a hard, non-porous surface can often be cleaned yourself with proper protection. The EPA's rule of thumb: if the mold covers more than about 10 square feet — roughly a 3-by-3-foot patch — call a professional. Always call a pro for mold inside walls, in the HVAC system, from sewage or flooding, or when vulnerable people live in the home. And fix the moisture source first: cleaning mold without fixing the water guarantees it comes back.
What's usually DIY-safe
- A small patch of surface mold on tile, glass, metal, or other hard non-porous surfaces.
- The moisture source is identified and fixed (a one-time splash, a window left open in the rain).
- You can protect yourself: gloves, goggles, and an N95 respirator — mold cleanup without breathing protection is a bad trade.
Clean it with a proper mold-cleaning product for the surface — not just bleach on porous materials, where it can't reach the roots. Scrub, dry the area completely, and watch it for a few weeks to confirm it doesn't return.
What's a professional's job
- More than about 10 square feet (EPA's guideline — roughly 3×3 feet).
- Hidden mold — inside walls, under flooring, behind cabinetry. What you see is the tip.
- HVAC systems — mold in ductwork or air handlers spreads through the whole house. Not a DIY zone.
- Sewage or flood damage — contaminated water changes the category entirely. Water categories →
- Vulnerable occupants — if anyone in the home has breathing difficulties, allergies, or immune concerns, bring in a pro and talk to a medical professional. This site doesn't give health advice.
Mold situations vary widely. This is general guidance, not a substitute for a qualified professional's assessment. This site does not give health advice — talk to a medical professional about any health concerns.