How Sewage Odors Get Trapped in Drywall and Flooring

Drywall is essentially a gypsum core wrapped in paper, and both layers are highly porous. When sewage water touches drywall, the liquid soaks in quickly, carrying bacteria and organic matter deep into the material. Even if the surface dries, the absorbed contaminants remain and continue to release odors.

The paper facing on drywall acts like a sponge, trapping particles that cause the smell. Over time, the odor can intensify as bacteria break down the organic material. In many cases, the only way to stop the smell is to cut out and replace the affected drywall sections.

• Paper surfaces absorb sewage moisture rapidly
• Gypsum core holds bacteria and organic matter
• Drying the surface does not remove trapped contaminants
• Odors can return when humidity rises
• Porous texture makes complete cleaning difficult

Surface cleaning with disinfectants can kill some bacteria, but it rarely reaches the deep pores of drywall or the underside of flooring. Sewage contains complex organic compounds that bond with porous materials. Standard household cleaners do not break down these compounds fully.

Professional cleaning methods, such as specialized enzyme treatments or ozone treatments, can help in some cases. However, if the material is heavily saturated, these treatments may not be enough. The pros often recommend replacement for porous materials that have been soaked with sewage.

Act quickly after a sewage backup to reduce the amount of material that absorbs the odor. Remove standing water and any solid waste, then ventilate the area to help dry surfaces. Avoid using fans that blow air into the rest of the house, as that can spread the smell.

Consider using a dehumidifier to lower moisture levels, which can slow bacterial growth. If you live in a humid climate, controlling indoor humidity is key. The pros can also use structural drying equipment to speed up the process, but replacement may still be needed.