"My son is in intensive care and has stopped breathing" were the first words heard by the project manager on a water damage job. What a great way to start a day! Details to follow...
Too often we fail to realize the absolute necessity of ensuring the complete dryness of structures on which we work. Many times contractors fail to measure the moisture content of the interior walls, ceilings, etc. and fail to complete the drying process. The drying is finished only when the structure reaches equilibrium with normal environmental conditions present. Equilibrium is a point at which no further loss or damage will occur and assessments and/or repairs can be made. When drying is not done, problems can occur such as a contractor experienced recently.
The contractor received a call from a previous customer reporting a new water damage. The scenario was fairly typical and sounded straightforward at first. A washing machine had overflowed, spilling up to 100 gallons of water on a vinyl floor in a utility room, an entryway, hallway and part of a master bedroom. The contractor responded the same day, and took remedial actions immediately. The customer elected to remove the carpet and pad as her son was very allergic to mold. The structure was then treated with a mildewcide/fungicide and a dehumidifier and airmovers were set up.
The following day the contractor discovered that the wood floor assumed to be over a crawlspace, was in fact a stringered floor over concrete. The vinyl, obviously damaged and in need of replacement, was removed. Because the insulation between the stringers was contaminated due to a small chronic leak, the insulation was removed, the exposed stringers and floor was treated for mildew, and air was moved in the exposed areas.
Within twenty-four hours, the homeowner's son was in the hospital intensive care after experiencing an allergic reaction (apparently to mold). He had gone into respiratory arrest and almost died. Naturally, the contractor was concerned and started asking questions. After going back to the job, he found an area that was twenty feet away from the water damage he was working on where the stringers measured 30% moisture. This area had not been damaged in the current loss, yet it was wet. Upon questioning the customer, it was discovered that a year ago they had experienced water damage in the still wet area. The water damage sat ignored for about six months and had subsequently been remodeled by a contractor without structural drying. The second contractor had inadvertently moved mold that had grown as a result of this wet structure, by simply attempting to dry the newly damaged area.The contractor had removed 100% of all the affected material that he had seen and measured as having an elevated moisture content. He did not go into another room in an area that had not received any moisture from the current loss and measure... it just didn't seem called for.
If the first contractor, during the remodeling, had addressed the problem of trapped moisture beneath the stringers and dried them, there would have been no problem with mold. Structural materials left to dry "on their own" usually take too long to dry, causing malodors due to biologic activity. Even the wrong equipment can take too long, such as drilling holes and letting a carpet dryer attempt to dry out the interior of a wall. Dry air has to be presented directly to the moisture laden material for drying to occur.
When moisture is introduced into the area beneath the plywood, it will almost surely remain trapped unless dry air in sufficient quantity is introduced, enabling the moisture to transfer to the air. The moist air is then moved out of the cavity and dehumidified.
I would caution that drying every false floor is neither practical nor advised. Some examples of problem situations or where you would not dry are:
Presence of pre-existing mold
Customer profile of allergies, asthma
Wet loose insulation
Delamination of plywood or other major structural problems such as wet or dry-rot
Vapor barrier with significant quantities of moisture trapped beneath it
Alternative demolition and replacement is less expensive
To dry a room such as this, you must have access to the areas along walls where the sleepers terminate (the butt ends). Carpet should be disengaged from the walls and holes drilled between the sleepers. A plastic barb can then be inserted into the hole. Pressurized air can then be injected into the plastic fitting through a drying system hooked up to a compressor providing enough air under pressure to overcome the resistance of the cavity. The other side of the room should be similarly disengaged and holes drilled to enable the air to escape from the cavity. Optimally, a drying system could operate on the other side of the room with negative pressure provided to both increase airflow and speed drying time. Switch the systems after several days to move air in the opposite direction to better equalize the substructure.
Care must be taken to ensure that all areas are equalized and moisture contents of structural materials are below the danger point. Measurements must be taken in a manner that will enable you to measure moisture in the sleepers and in the insulation. This can usually be accomplished through the carpet, although it is much easier to measure with the carpet moved back.
Don't leave wet materials behind to cause health or structural problems for anyone, let alone you. If the structure is dried thoroughly, you will not be the cause of a frantic phone call to 911.
