The short answer
Common Sources of Rain Moisture
When rain falls, water follows gravity and finds any gap in your home's envelope. Check the roof for missing or damaged shingles, and look at the flashing around chimneys and vents. Gutters that are clogged can overflow and send water down the exterior walls, where it can sneak behind siding and into the structure.
Windows and doors are another frequent entry point. Worn weatherstripping or cracked caulk lets rainwater run inside. The foundation can also be the culprit, especially if the soil slopes toward the house, causing water to pool against the basement walls. Even a small crack can allow enough moisture to create a persistent musty smell.
How Mold and Mildew Grow
Mold spores are always present in the air, both indoors and out. They only need two things to grow: a food source and moisture. Your home's building materials, such as wood, drywall, and carpet, provide plenty of food. When rain adds moisture, the spores settle and multiply, often within 24 to 48 hours.
As mold colonies grow, they produce microbial volatile organic compounds (MVOCs) that have a distinct earthy, musty odor. This smell is often the first sign of a hidden moisture problem. The longer the area stays damp, the stronger the odor becomes, and the more extensive the mold growth can get.
- Check the attic for water stains on the roof sheathing
- Inspect the basement for damp spots on walls or floors
- Look for water stains on ceilings or walls near exterior edges
- Smell around windows and door frames for a concentrated odor
- Feel for dampness in carpet near exterior walls
- Examine the crawl space for standing water or wet insulation
Steps to Find the Leak
Start by walking through your home during a rainstorm. Look for water drips, damp spots, or discoloration on ceilings, walls, and floors. Pay special attention to corners, around skylights, and near any penetrations like vents or pipes. Use a flashlight to inspect dark areas like attics and crawl spaces.
If you don't see obvious water, the leak may be hidden behind walls or under flooring. A moisture meter can help detect dampness in building materials. You can also hire a professional to perform a water damage inspection, which often includes thermal imaging to find hidden moisture without tearing things apart.
Dry and Clean the Damp Area
Once you find the source, stop the water entry first. For a roof leak, a temporary patch may hold until a roofer can make permanent repairs. For foundation issues, improve drainage by extending downspouts and regrading the soil. Then, dry the affected area thoroughly using fans and a dehumidifier.
Clean the moldy surfaces with a mild detergent and water. For porous materials like drywall or carpet, you may need to remove and replace them if they are heavily contaminated. The goal is to remove the mold and its food source, not just mask the smell with air fresheners.
- Remove wet carpet and padding to allow the subfloor to dry
- Cut away and replace water-damaged drywall
- Scrub non-porous surfaces with a detergent solution
- Run a dehumidifier for several days until the area is fully dry
- Discard any materials that cannot be dried completely
When to Call the Pros
If the leak is large, hidden, or has been present for a while, you may need professional help. Local water damage pros have the tools to find hidden moisture and to dry structures thoroughly. They can also handle the safe removal of moldy materials and the cleaning of affected areas.
If you live in Arlington, you can search for water damage restoration services in your area. They often provide water damage inspection, drywall repair, and flooring removal. You can also contact your insurance company to see if your policy covers the damage. Policies vary, and your insurer decides what is covered.
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Every hour counts once water gets into floors and walls. One call starts the response.
Call Now (703) 462-1739Frequently asked questions
Can a musty smell be dangerous?
The smell itself is not toxic, but it can indicate mold growth. Mold can cause allergic reactions, respiratory issues, and other health problems, especially for people with asthma or sensitivities. If you feel unwell, see a doctor. The right approach is to address the moisture and mold without delay.
How do I know if it's a leak or just high humidity?
If the smell only appears during rain, it's likely a leak. High humidity usually causes a musty smell that persists regardless of weather. Check for visible water stains or damp spots. A moisture meter can help. If you find any, it's a leak.
Should I clean mold myself?
For small areas (less than 10 square feet), you can clean it with detergent and water. Wear gloves and a mask. For larger areas or if the mold is in drywall or insulation, it's safer to hire a mold professional. They have the equipment to contain spores and remove contaminated materials properly.
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