The short answer
What Wall Lath Is and How It Gets Wet
Wall lath is the structural layer behind plaster walls, typically made of narrow wood strips or metal mesh. It provides a base for the plaster to adhere to. Water reaches the lath through leaks from plumbing, roofs, windows, or foundation walls. Because it is hidden, the lath can stay wet long after the initial leak, creating a persistent dampness. This trapped moisture does not dry out on its own.
In many climates, seasonal temperature shifts can stress pipes and building materials. A small, slow leak inside a wall cavity can go unnoticed for months. The lath acts like a sponge, absorbing water and holding it against the back of the plaster. This trapped moisture does not dry out on its own.
The Link Between Moist Lath and Odors
The musty, earthy smell from your wall is a direct byproduct of microbial growth. Mold and mildew spores are present everywhere, and they begin to colonize organic materials like wood lath within 24 to 48 hours of getting wet. The smell comes from microbial volatile organic compounds, or MVOCs, which are gases released as these organisms live and feed.
If the lath is wood, the moisture also initiates wood rot. This decay process breaks down the wood fibers, producing a distinct, sour smell. The combination of active mold growth and decaying material creates a strong odor that can seep through the plaster and into your living space. The smell often gets worse in humid conditions or when the wall is warm.
Risks of Ignoring a Lath Smell
Ignoring the odor is a mistake because the problem will not fix itself. The ongoing moisture will continue to degrade the wood lath and potentially the wall studs, compromising the wall's structural integrity. Persistent dampness can also damage electrical wiring within the wall, creating a potential fire hazard. The smell is a clear warning that conditions inside the wall are not healthy.
More importantly, the mold growing on the lath can affect your indoor air quality. Air currents can carry spores and microbial gases into your home through outlets and gaps. For people with allergies or asthma, this can trigger respiratory symptoms. You should see a doctor if you or a family member feels unwell and suspects a mold issue.
- Progressive structural damage to wood framing.
- Potential for electrical hazards from wet wiring.
- Persistent poor indoor air quality and odors.
- Expansion of mold growth to other areas.
- Increased cost and scope of future repairs.
- Possible voiding of home insurance coverage if neglect is proven.
How Professionals Find and Address the Source
Local water damage pros start by identifying the exact source of the water. This involves specialized tools like moisture meters and thermal imaging cameras to map the extent of wetness without unnecessary demolition. They look for the highest moisture reading, which points directly to the leak's origin, whether it's a pipe, roof flaw, or condensation issue.
Once the leak is stopped, the focus shifts to drying. The pros create strategic openings in the plaster or drywall to expose the cavity. They then use industrial air movers and dehumidifiers to dry the lath, studs, and insulation thoroughly. This process removes the moisture that fuels the odor, stopping the mold growth at its source.
Repairing the Damage and Preventing Recurrence
After the structure is completely dry, damaged materials must be removed. Rotten wood lath and insulation are discarded. Any remaining mold on structural wood is cleaned following established guidelines for mold remediation. New lath and plaster or drywall are then installed to restore the wall. This full repair eliminates the smell and returns the wall to a safe, stable condition.
To prevent the problem from returning, address the root cause. Fix any plumbing issues, ensure your roof and flashing are sound, and improve drainage around your foundation. In kitchens and bathrooms, use exhaust fans to reduce humidity. Regularly check under sinks and around appliances for signs of moisture. In regions with freeze-thaw cycles, be extra vigilant about checking for leaks after cold snaps.
- Permanently repair the leak, whether plumbing, roofing, or siding.
- Ensure the wall cavity is completely dry before closing it up.
- Replace all water-compromised lath, insulation, and plaster.
- Consider adding a vapor barrier in high-humidity areas during repair.
- Maintain good ventilation in moisture-prone rooms like bathrooms.
- Schedule regular home maintenance checks for potential water entry points.
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Call Now (208) 537-2633Frequently asked questions
Can I just paint over the smell?
Painting only traps the odor and moisture, making the problem worse. The mold will continue to grow behind the paint, damaging the structure. The smell will eventually seep through. You must address the underlying water damage and dry the materials completely.
Does insurance cover lath and plaster water damage?
Coverage depends on the source of the water. Sudden, accidental events like a burst pipe are often covered, while damage from long-term neglect may not be. Policies vary, and your insurer decides what is covered. Document everything and check your policy details.
How long does it take for the smell to go away after repairs?
The smell should dissipate quickly once the wet materials are removed and the area is dried. However, a faint odor may linger in the room for a few days as air clears. Using an air purifier with a HEPA filter can help remove remaining spores and odor particles.