Musty Smell in the House? When Mold Testing Is Worth It

"I get a musty smell in my house and I can't figure out the source"

That is almost word for word how one Pacific Northwest homeowner started a forum post. Another described "an overpowering musty, dank odor" every spring and fall and wrote, "My gut feeling is that it is mold but I cannot locate a concentrated source." A third asked the question most people end up at: "who can I call upon to locate it?"

If that sounds like your house, you are in the right place. A musty smell almost always means moisture is somewhere it should not be. The job is to find it.

Where the smell usually comes from in Oregon homes

• The crawlspace. In the Willamette Valley, this is the first place to look. Wet soil, torn vapor barrier, sagging insulation, or standing water under the house can send musty air up through the floors and ducts. Our guide to crawlspace moisture and encapsulation goes deeper on this.

• Under sinks and behind appliances. Slow drips under the kitchen sink, behind the dishwasher, or at the fridge water line.

• Bathrooms. Behind the toilet, around the tub, and in walls behind a shower with failed grout or caulk.

• Exterior walls and windows. Leaky window flashing can let rain into the wall cavity.

• Attics. Roof leaks and poor ventilation can leave condensation on the underside of the roof deck.

• After a past leak. Areas that got wet and were never fully dried. See how secondary water damage starts.

What you can check yourself first

• Notice when the smell is strongest. When the furnace runs? After rain? In one room?

• Open the cabinets under every sink and look and feel for dampness or stains.

• Look at baseboards and the bottom of walls for staining, peeling paint, or swelling.

• If you can safely look into the crawlspace, check for standing water, fallen insulation, or a damp earthy smell at the hatch.

• Pick up a simple humidity meter. The EPA recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent.

When a professional mold inspection is worth it

• You smell mold but cannot see it. An inspector uses moisture meters and a thermal camera to find wet areas behind walls, under floors, and in the crawlspace.

• You had water damage recently and want to know if it was fully dried.

• You are buying or selling a home and an inspection report mentions moisture or mold.

• Someone in the house has health concerns and you want to know what you are dealing with before deciding anything.

• You are filing an insurance claim and need the moisture source and extent documented.

• After remediation, to confirm the problem is actually gone.

When you probably do not need testing

• You can see the mold and it is small. The EPA says if the moldy area is less than about 10 square feet, in most cases you can handle the job yourself. Fix the moisture, clean it, and watch for it to return.

• You already know the source. If the cause is obvious, money is better spent fixing the moisture and removing the mold than proving it is there.

• Shower mildew. Surface mildew on grout and caulk is usually a ventilation and cleaning issue.

Lab testing tells you what kind of mold is present and how much is in the air. It does not tell you where the water is coming from. Finding and fixing the moisture is what actually solves the problem.

What a mold inspection includes

• A walk-through of the problem areas and the usual suspects, including the crawlspace and attic.

• Moisture readings and thermal imaging to find hidden water.

• Air or surface samples sent to a lab, only if the situation calls for it.

• A plain explanation of what was found and what it would take to fix it.

Cost depends on the size of the home and whether lab samples are needed. Harris includes mold in our free inspection, so you can find out what you are dealing with before paying for anything.

A word on scare tactics

Homeowners who have been through mold jobs say things like, "They either have no idea what mold is, or they use scare tactics to separate you from your money." Another said a contractor "could have convinced me the entire subfloor needed replacing, but instead, he was honest."

Some mold is a minor cleanup. Some is a bigger job. A good inspector shows you the readings, explains what they mean, and tells you which one you have. One of our customers, whose concern started with water coming through a heating vent, wrote that our team "took the time to explain what they were checking, answered all of our questions without rushing, and left us feeling reassured."

Should you clean it yourself?

For a small area on a hard surface, often yes. Wear gloves, an N95 mask, and eye protection. Do not dry-brush or sand it, which spreads spores. Do not just spray and paint over it. If it comes back, the moisture source is still there.

Call a pro if the area is large, it is inside walls or in the crawlspace, the HVAC system smells musty, it keeps coming back, or anyone in the house is sensitive to it.

Find the source and fix it

Harris Restoration inspects for hidden moisture, finds the source, and removes mold with containment when it is needed. If the mold came from a sudden water event, our in-house public adjuster, Nataie, who is fully IICRC certified, can help with the claim. Call (971) 267-2779 or request an inspection. Learn more about our mold remediation service.