A musty smell after a leak, nothing visible. Find the moisture first.
A musty smell is usually growth you cannot see, and the fix starts with finding what is still damp.
What is probably happening
- Something from the leak is still wet: the back of drywall, under a vanity, carpet pad, or insulation in a wall or ceiling.
- The EPA says mold can be hidden behind drywall, wallpaper or paneling, on the top of ceiling tiles, or under carpets and pads.
- The smell is a moisture signal. A moisture meter finds it; an air test does not tell you where it is.
Do this in the next five minutes
- Walk the area with your nose and your hand. Cabinets, closets, behind furniture on the wet wall, under the sink.
- Pull the carpet edge and look at the pad. Pull a baseboard on the suspect wall.
- Run a dehumidifier in the room and keep the doors open.
- Photograph anything you find.
- Book a moisture inspection. Ask for a company that will meter and open small areas, not one that leads with air sampling.
Do not
- Do not buy an air quality test as the first step. It tells you spores are present, which the smell already told you.
- Do not spray bleach on painted drywall and call it done. It does not reach the back of the board, and the CDC says never mix bleach with other cleaners.
- Do not hire the same company to test and to remove.
Who to call
A water damage restoration company, for a moisture inspection
The first job is finding what is wet and drying it. If opening the wall shows growth, that becomes a remediation scope, ideally by a different company than the one that found it.
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What it should cost
$303 to $1,045
Mold inspection, typical range, average $671. If remediation is then needed, $1,223 to $3,757.
Source: Angi, mold inspection cost, updated July 2026. View source
National published range, not a quote for your job. The full cost table for this trade is on the water damage page.
Ask this contractor, on the phone, before anyone comes out
Tap each one as you ask it.
- Will you use a moisture meter and open small inspection holes, or only take air samples?
- If you find it, do you also remove it, and would you write that as a separate scope?
- What is the moisture source, and is it fixed?
- Does my state require a mold licence for remediation, and do you hold one?
End the call if
- Air testing sold before anyone has looked behind a wall.
- A remediation quote from the company that did the testing.
- A whole-house 'treatment' or fogging offered as the fix.