This week

10 to 100 square feet: a contractor job with containment

The source is fixed, so the growth has stopped. The EPA's remediation guide calls for limited containment at this size, which is contractor work. In Texas anything over 25 contiguous square feet needs a licensed remediator.

What is probably happening

A leak or long term damp that ran for a while before it was noticed.
Drywall that has mold on the face usually has it on the back too. The EPA notes growth on the back side of drywall, wallpaper and paneling. Expect the panel to be cut out.
There may be more behind the wall than you can see.

Do this in the next five minutes

Photograph and measure every patch. Write the total square feet on the photo.
Close the room off. Do not run a fan or open the HVAC register in that room.
Confirm the leak is really fixed. Look for staining that is still growing.
Get two or three written quotes that name the square footage and the method.
If your state licenses mold work (Florida, Texas, New York, Louisiana, DC), look the license up yourself on the state site.

Do not

Do not tear out the drywall yourself. At this size the EPA calls for containment, and cutting it open without containment sends spores through the house.
Do not strip wallpaper to see what is under it. The EPA warns removal of wallpaper can release a massive amount of spores.
Do not pay for an air test first. The EPA says sampling is unnecessary when mold is visible.

Who to call

A mold remediation contractor

This is removal under containment, not drying. If the wall is still wet you need restoration first, but you told us it is dry.

Get a free shortlist The seven questions for this trade

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What it should cost

$1,223 to $3,757

Typical range, national average $2,368, or $10 to $25 per square foot. Wall mold runs $1,000 to $20,000 depending on how far it goes

Source: Angi, mold remediation cost, July 2026. View source

National published range, not a quote for your job. The full cost table for this trade is on the mold page.

Ask this contractor, on the phone, before anyone comes out

Tap each one as you ask it.

How many square feet are you pricing, and what containment will you set up?
Will you run negative air and HEPA vacuum the area when done?
What gets removed and what gets cleaned, and why?
Who does post remediation verification, and is it someone other than you?
Did your company also do the testing that found this?

End the call if

A quote written against a 'safe mold level' or a code violation. The EPA says no federal limits for airborne mold exist.
The tester is also the remover. Florida and Texas law bar the same company from doing both on the same job.
A large deposit before a written scope.

Insurance. Mold is generally covered only when it follows a covered sudden water loss such as a burst pipe. Gradual leaks and seepage are excluded, and flood needs a separate policy. (Texas Department of Insurance)

Where this comes from

Not my problem, tap through instead Every mold answer