Musty Smells Under Floorboards

Many old homes have a distinct musty smell. This smell often comes from under the floorboards and is therefore impossible to remove by simply cleaning interior surfaces. Musty smells can prevent you from enjoying the home and in some cases can actually come from a potentially toxic compound. The smell might be coming from one or several sources. Understand the source of the smell to determine how to fix it.

Musty smells can seep up from under floorboards.


Mold is a type of fungus that breaks down organic matter and is attracted to areas with a lot of moisture and little air ventilation. This makes the area under damp floorboards a prime spot for mold growth. When mold breaks down organic matter, it releases volatile organic compounds (VOCs) that create a musty odor. Breathing in a high level of VOCs for a prolonged period of time can cause headaches, dizziness and adversely affect short-term memory.


When dust accumulates in an area, it brings with it a dank and musty smell. Dust is generally composed from microscopic pieces of skin residue, body oils, dirt, dust mites and other small contaminants. Dust is impossible to prevent completely, but an old house may have accumulated a lot of dust under the floorboards. This is especially possible if the floorboards weren't sealed properly.

Removing Mold and Musty Odors

Remove the musty smell from mold growth by first installing a dehumidifier in your home. This will lower the relative humidity, making your home inhospitable to mold growth. This can kill mold from under the floorboards, but it might take a while for the smell to dissipate. Alternatively, rip up the floorboards to access the mold and remove it with a mold-killing solution, such as one part bleach to 10 parts water. Spray the solution over the mold and scour it with a scrubbing brush.

Removing Dust and Musty Odors

Remove musty odors from excess dust by installing an air purifier in your home. Air purifiers with small filters will actually remove the dust particles in the air that cause the musty odor. It might take several days or weeks for an air purifier to completely remove the smell, but it might prevent you from having to tear up the floorboards to access and remove the excessive dust. Tearing up the floorboards might be the only option, however, if the floorboards weren't installed properly.