Beyond the direct water damage from a flood, there can be short term and long term problems with mold growth, whether the building is commercial or residential.
The source of the water is the first important issue. Consider the following:
1.) If the flood is from surface water flooding such as heavy rains, hurricanes, and overflowing rivers this means dirt and debris. This material is a rich growth environment for mold and bacteria as well. It is full of lawn fertilizer, top soil, plant debris and even sewage that promotes many microorganisms to grow - and rapidly.
This debris will fully penetrate carpets, cloth covered surfaces, and wall boards with little chance they can be thoroughly cleaned or disinfected. With few exceptions, the remedy is removal and replacement. It is important to note that bacteria can contaminate all surfaces where possible septic waste is involved. Testing for e. coli is important.
There are other issues of a more general nature that will be covered later in this article.
2.) If the flood is from a backed up sewer – then it is obvious that both mold and bacteria are important issues that must be addressed. Replacement of ducts, and contacted surfaces is highly advised. Very thorough cleaning of clothing and other fabrics is essential (dry cleaning won’t work since it doesn’t disinfect). Cleaning of all dirt and debris is as important as removing mold or bacteria since the microorganisms can exist in a dormant state and only need a “little something to eat” – such as dirt.
3.) Flooding from a broken or leaking water line is not to be dismissed as a non-microbial event. Since small quantities of molds and mold spores are essentially everywhere (in the air and on most horizontal and vertical surfaces), they only need a source of moisture and food which can be: a). the cellulose in sheetrock, b). wood, c). cotton, wool or other natural fibers, d). dust/dirt that accumulates over time.
Regardless of source and the specifics mentioned above, there are some things that can be done to prevent or control mold growth after a flood.
The first is to clean up and remove all damaged or destroyed furnishings or building materials as soon as possible. This will reduce mold growth and the quantity of mold and spores that can multiply and be dislodged to settle elsewhere. If allowed time to infest an area, just the demolition process itself can release millions - even billions - of spores.
Dehumidify the area even while clean up is going on – don’t wait until demolition is complete. Those little microbes aren’t shy; they’ll grow whether they see you or not.
Air conditioning or keeping the area cool can be very effective. Air conditioning de-humidifies as well as cools, which removes heat and moisture – both of which are essential for mold growth.
Remember that wood, spaces behind walls, underneath furniture, equipment, appliances, and even sub-flooring can harbor water or high levels of moisture that are very conducive to mold propagation. If moisture is a long term problem, replacing material with non-porous or less porous material is advisable, ie greenboard (water resistant sheetrock), hardboard, metal studs, ceramic tile, etc.
Fungicidal paint can be used to retard (not eliminate) mold growth in areas that have been wet or damp over an extended period of time. I’m not referring to normal latex or other water based paints that contain mold/bacteria retardants in them while in the container. Most major manufacturers of household and commercial paint carry a line of fungicidal paints developed to retard mold growth after application.
Controlling microbial growth after flooding is a subject that can (and does) cover volumes. This article just summarizes some of the most important aspects of this very complex subject. Consulting an expert should be considered in severe cases or for large buildings.