Construction Dryouts

Dry Buildings with Heat®

Oftentimes new structures are built with green or wet lumber that is high in moisture content. Materials delivered to or stored at a construction site during wet weather may not have time to dry prior to construction. Poorly stored timbers may collect moisture. When problems occur during construction as a result of inclement weather, high humidity, or other conditions resulting in vapor intrusion and condensation on structural members, contractors may choose to use wet materials to continue construction. As a result of any of these conditions, new construction with wet building materials can become a serious problem that may end with unhealthy structures and damages from construction defects.

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Damages from Wet Construction Materials

According to the USDA’s Forest Products Laboratory (FPL), “Softwood lumber intended for framing in construction is usually targeted for drying to an average moisture content of 15%, not to exceed 19%.” Ideally, construction timbers would arrive at the jobsite at the moisture content suitable for the intended use.  This would solve any problems caused by drying and shrinkage.  This is difficult to achieve.  Ultimately, construction lumber will reach equilibrium levels that reflect the local climate which may range from as low as 4-6% in desert areas to 12-15% in coastal or humid regions. Shrinkage and warping occurs during the drying process.  If the timbers are green, the moisture levels are equal or higher than 28% and drying from this point creates the most shrinkage. Many construction experts believe it is important that framing materials are below 19% moisture and preferably near average equilibrium levels before they are enclosed.

Concerns stated from the FPL from excessive moisture are several, including, shrinkage may cause loosening of fastenings and settling of the building with resulting plaster cracks, drywall nail popping, and unsightly openings around trim and moldings. Excessive shrinking of studs, sheathing, and siding decreases the weathertightness of walls, loosens fastenings, and may reduce the mechanical stiffness of walls. Once the framing is enclosed, it is not possible to make corrections to these problems. These problems can be the source of many significant construction defect issues. Additionally, construction defects can allow moisture intrusion leading to adverse health effects. The FPL also cautions that drying timber construction materials below their ultimate ambient levels can also cause problems as the materials may result in swelling as they reach equilibrium; causing doors, windows and drawers to stick.

Health Effects from Wet Construction Materials

It is well known that damp structures are unhealthy structures. Newly constructed buildings may have fungal growth that occurred prior to or during construction. If this growth continues to receive adequate levels of moisture it can lead to both serious decay potential and an unhealthy structure. Mold problems may be found in structures that have never leaked because of these types of problems occurring during construction. A more serious problem can occur from building defects that resulted from shrinkage or warping of framing materials after the frame was enclosed. These types of problems can allow moisture to enter the structure from rain or even high humidity levels. There are many significant studies that illustrate the relationship between water damaged structures and health effects.

Damp Indoor Spaces and Health, published in 2004 by The Institute of Medicine, found a relationship between damp indoor environments and adverse health outcomes. This comprehensive review of literature found sufficient evidence of an association between damp indoor spaces and a variety of respiratory symptoms including upper respiratory tract symptoms, cough, wheeze, and asthma symptoms in sensitized persons.

More recent reviews of literature by the US Government Accountability Office (GAO, 2008) report, the World Health Organization report (WHO, 2009), the National Institute of Occupational Safety and Health (NIOSH), and the Lawrence Berkeley National Laboratory/EPA (Fisk, 2007) study provide additional support for these earlier conclusions and extend the concerns. The Executive Summary of the WHO report stated “Exposure to microbial contaminants is clinically associated with respiratory symptoms, allergies, asthma and immunological reactions.” Clearly, a relationship exists between damp structures and health effects.

ThermaPureHeat® is a Solution for Construction Dryouts

If high moisture levels are detected, application of the ThermaPureHeat® process after framing and sheathing can reduce moisture levels to the intended ambient levels of 6-12% depending on intended use and geographic location. The ideal objective is to reach or be slightly above average equilibrium moisture levels. If this process is complete prior to construction of vapor barriers and erection of sheet rock walls, mold should not colonize or amplify within the structure. Additionally, finish shrinkage will not occur to any great extent preventing both building and visual defects. It is important that the building’s frame reaches dimensional stability prior to enclosure to prevent significant additional shrinkage and warping. ThermaPureHeat® is an excellent preventive measure during the construction process. Additionally, structural pasteurization will provide other benefits in preparing the new structure for a healthy occupancy, such as elimination of structural pests and the reduction of VOCs from engineered products.

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