Disinfect and Treat
When performing flood remediation after the house is “clean” from the previous step, the structure needs to be treated and sprayed once again to kill any remaining bacteria and microbial residue – mold removal This is done again with a compressed air sprayer and a product like Microban (bleach is not the best option, as it is very caustic and does not work as well as the commercial disinfectants). All surfaces need to be sprayed liberally (they don’t have to be “soaked”). Spray from the 4’ cut line down and across all floors and remaining surfaces. Pay careful attention to spray BOTH sides of studs and ins and outs of all nooks and crannies. Your restoration contractor should have experience with mold removal.
Structural Drying and Moisture Removal
This next step of flood remediation is another big area of misunderstanding. Mostly because this is where the scientific portion kicks in and where people really need to depend on a professional or at least get the CORRECT tools to do the job. The first step in this process is to establish a base line moisture reading at a minimum of two different heights (depends on water depth in the house) and in each room. The location(s) that we use are at the sill plate of the wall (bottom most wood board laid against the slab) and at about 18” up on the wall studs. The science starts with the baseline drying standard for HOUSTON TX (it varies in different parts of the country). The FEMA standard for moisture content in wood in Houston is 16%. Any wood measuring above 16% needs to be dried and is considered “wet”. If you were to go to home depot and purchase a new 2×4, it would most likely read at about 15-16% moisture content. Different parts of the country with lower average humidity levels will have a lower drying standard and moisture content. As far as determining the moisture level in the wood in your home, a PIN-BASED moisture meter is the BEST device/most accurate reading (or an infrared meter – but they are $1000). The pin-based meter will get approx. 1/2” down into the wood and tell you if the interior of the wood is dry yet (not just the surface of the wood). Wood dries from the outside in, so the surface will be dry long before the center of the board. As far as the FEMA protocol is concerned base line reading for moisture must be established before drying begins (they want to see the starting point and a downward trend in the moisture content). FEMA requires a drying log and daily monitoring to pay for the structural drying of your home. The daily readings need to include those moisture measurements as well as relative humidity and temperature in the home. There is no specific number for the relative humidity, but the lower the number the better and the faster the home will dry out. On homes with commercial drying equipment in them, we have been seeing readings in the 40-50% relative humidity range and have been able to get the moisture content of the wood down to around 12-14%. Regarding the TYPE and QUANTITY of equipment needed to properly dry out a house – commercial grade dehumidifiers and fans are the way to go and most effective at properly drying a home. There is a science to it and consumer available dehumidifiers (from Home Depot/Lowes) don’t quite cut it. They (consumer models) as well as your home’s HVAC system do a good job of removing moisture from the air, but they do a poor job (or lengthy job) of removing the moisture from the structure. They can/will work, but over a LONG period of time and may not ever get down below certain moisture content. On the scientific side, moisture moves from wet to dry, so having dry air in your home encourages the moisture in the structure (studs and concrete) to move from the wet materials to the air itself and then the air itself is dried by the dehumidifiers. The type that work best in the Houston area are called LGR dehumidifiers (Low Grain Refrigerant). The general guideline for equipment is one LGR dehumidifier per 750-1000 sqft and 6-8 fans per dehumidifier. The actual number of fans depends on the layout of the home… The fans need to meet a certain CFM rating to be approved by FEMA; a normal box fan won’t cut it. With the right amount of equipment in a home and the right weather conditions, it could be dried out in as little as 2 days, with the average being about 3 days. There is no magic number for the number of days; it needs to be based on actual moisture readings and drying of the structure below 16%. Again an accurate detailed drying log MUST be maintained on the home to ensure that FEMA covers the costs and more importantly to ensure that your home was dried correctly. All moisture has to be handled for mold removal. Flood remediation procedures done by a qualified professional should prevent further mold growth.