Effects of Moisture
Concrete is one of the least understood and least predictable materials in the construction and remediation industries. Moisture travels great distances through concrete when it is wet. When concrete slabs are placed directly on the ground without a proper capillary break, such as gravel, the concrete can absorb additional water from the soil. Other contributors to ground and concrete saturation include an improperly designed, installed, or even nonexistent drainage system.
There are many factors that affect the appearance, durability, strength, porosity, and density of concrete. Individually and collectively, variations in these factors will influence how water is either absorbed or desorbed by concrete. The resulting unpredictability of how concrete reacts to moisture requires remediators to evaluate on-going concrete drying progress, which typically is not uniform. Changes in drying techniques, even within the same structure, as well as from job to job, are often required to completely dry all areas. Generally, concrete tends to release moisture more slowly than most other building materials. Lightweight concrete releases moisture even more slowly than concrete typically found in most flooring systems. Lightweight concrete is typically 3/8″ to 1 ½ ” thick and usually found over plywood. Post-tensioned concrete absorbs moisture even more slowly, due to compaction.
Concrete does not create a favorable growing environment for mold;
Paper-Faced Gypsum (Drywall)
Drywall loses its structural integrity when saturated, but regains it if dried properly. It should be classified as porous when making decisions about removal based on the Category of water. For example, in Category 3 losses, drywall should be removed to allow remediators access to pockets of saturation for thorough cleaning and drying to acceptable moisture content (MC). Paper-faced gypsum readily supports mold growth if left wet for a sufficient period of time.
Metal Structural and Decorative Components
These items are non-porous; do not absorb moisture readily and are not directly susceptible mold growth. Moisture can cause· corrosion and deterioration of metal surfaces or the materials to which they are attached.
Solid wood can be either soft or hardwood species. Solid wood materials can include: framing, flooring, and trim. It should be classified as semi-porous material when making decisions about removal or replacement, considering the Category of water. For example, when Category 3 water penetrates behind or underneath solid wood molding or flooring, the material should be removed to expose pockets of saturation and contamination for thorough cleaning and drying to acceptable moisture content (MC). When the moisture content of wood exceeds 16%, it is more susceptible to mold growth.
Engineered Wood Products
Engineered wood products include laminated wood beams, floor joists and other framing structural materials. They should be treated as semi-porous materials when making decisions about removal or replacement, considering the Category of water. When the moisture content of wood exceeds 16%, it is more susceptible to mold growth.
Housewraps/ Vapor/ Air Retarders
The primary function of housewrap is to provide air and moisture control. Building paper and housewrap are installed in wall assemblies to prevent water penetration. Breakdown in this material increases the chance of water entering into the building envelope. Wood tannins can cause housewrap to become more permeable to water. Also, some additives in stucco can act as surfactants that promote penetration of moisture, and thereby lower the effectiveness of housewrap as a moisture retarder.
Insulation may be manufactured from mineral materials, such as slag from steel mills (e.g., rock wool). In water damage situations, the batt form of rock wool insulation generally retains its loft or bulk after drying. When loose-fill rock wool becomes wet, it can compact and lose loft and R-value. Therefore, such insulation should be removed and replaced regardless of the Category of water.
Interior Duct Insulation
When internal ductwork insulation gets wet or is contaminated, it should be removed and replaced with new ductwork, according to NADCA ACR 2013 or current version Assessment, Cleaning and Restoration of HV AC Systems.
Masonry (e.g., Bricks and Blocks)
The movement of water in and out of masonry wall assemblies should be considered when applying drying procedures. Wind-driven rain, capillary action and water vapor are sources of water in masonry walls. Integral water repellents,· surface treatments and wall drainage can greatly reduce the absorption characteristics of masonry. Properly tooled mortar joints also play a role in the water tightness of finished buildings.
Masonry does not create a favorable growing environment for mold; however, susceptible building materials in contact with wet masonry can develop mold growth. Due to the extended length of time that is required to dry wet masonry, uncontrolled evaporating moisture can contribute to higher relative humidity and result in secondary damage.
Vinyl and Vinyl Composition Tile (VCT) Type Materials
While these materials do not absorb water, at least on their surfaces, when water penetrates underneath, they often need to be replaced due to failure of mastics, and for access to dry wet substrate materials.
Glass, High Density Plastics, Ceramic and Porcelain Materials
These items are non-porous; do not absorb moisture readily, and are not directly susceptible to mold growth. Moisture may cause failure of mastics and deterioration of materials to which they are attached.
Plywood should be classified as a semi-porous material when making decisions about removal or replacement, considering the Category of water and time of exposure. When the moisture content of wood exceeds 16%, it is more susceptible to mold growth.
Particle Board and Fiberboard
When wet, these materials can swell, absorb water and lose shape and strength, and therefore, they often require replacement. When the moisture content of wood exceeds 16%, it is more susceptible to mold growth.
The effectiveness of insulation is measured using a scale of R-values. The higher the R-value, the greater the resistance to heat transfer. All building products have an R-value. The U.S. Department of Energy has published a model energy code that recommends minimum insulation requirements for different climates of the United States. Generally, these are prescriptive in nature. For example, climate zone 4 recommendations are: R3 8 for ceilings, Rl9 for walls, and Rl9 for crawlspaces or basement floors.
Proper placement of insulation in a building is climate-specific. When insulation has not been placed properly, construction failures and building-related problems can be linked to this defect. Insulation affects comfort, durability, energy efficiency, and indoor environmental quality.
Basic principles explain the loss of insulation effectiveness. First, insulation works by trapping air or millions of tiny air bubbles. It is this air that insulates, just as air in a goose-down coat or comforter keeps a person warm. Second, water has much higher thermal conductivity than air. Moisture as a liquid or vapor can cause insulation to lose its ability to resist heat transfer. This means that moisture short-circuits the ability of insulation to perform its function in resisting heat transfer.
Insulation should be considered a porous material when making decisions regarding drying or replacing. Insulation saturated with Category 2 or 3water should be replaced. When remediators replace insulation, they should maintain the integrity of the vapor retarder as it was originally designed.
This insulation is manufactured from sand and minerals. In water damage situations, the batt form of fiberglass insulation generally retains its loft after drying. When loose-fill fiberglass becomes wet, generally, it can compact and lose loft. If compacted, remediators should remove fiberglass insulation and, after drying structural components, replace it with new material, regardless of the Category of water.
Electrical, Plumbing, HV AC Components and Mechanical Systems
These systems should be evaluated by a specialized expert
Plaster and Stucco
While these porous materials may retain their structural integrity, decisions about removal or replacement should be made based on the contamination and location of the material (e.g., interior, exterior). Remediation options can include: drying in place; drying from above, below, or behind; or complete removal in Category 3 losses for access to pockets of saturation to thoroughly clean and sanitize.
Plaster and stucco do not create a favorable growing environment for mold; however, susceptible building materials in contact with plaster or stucco can develop mold growth. Due to the extended length of time that is required to dry these materials, uncontrolled evaporating moisture can contribute to higher relative humidity and result in secondary damage.
Windows and Doors
Depending on construction components, windows and doors vary from semi-porous to non-porous. Each needs to be handled according to its composition.
Properly installing windows along with properly integrating drainage planes, flashing, and weather-resistant barriers are key components in preventing moisture migration into building walls. Properly installed three-dimensional sill flashing is seamless and fully protects the rough opening. A weep system that provides a potential escape path for water should be created at the bottom of windows to eliminate the need. for caulk· at the bottom flange. Windows with weep holes and flashed openings should not be caulked.
There are many types and grades of laminate flooring. The layers of resin, high-density or medium-density fiberboard, and resin-saturated photographic paper are bonded with heat and pressure to form a direct-pressure laminate (DPL) or high-pressure laminate (HPL), after which a wear layer is applied.
Laminated flooring can resist impact damage and scratching based on its abrasion class (AC) rating. Because fiberboard is highly hygroscopic, any water that gets past the photographic layer can absorb and distort edges,
causing swelling and delamination. Some grades of laminate add higher resin content, waxes, and oils to slow moisture absorption. Most laminate product maintenance instructions discourage wet mopping or “submersion cleaning.” Therefore, water intrusions can quickly lead to deterioration. Laminate products do not respond well to the vacuum floor drying systems used on other hard surface floors. Often, laminates are installed over a thin cushion material. On concrete, a three-mil plastic vapor barrier is often installed underneath the flooring. When significant water penetrates under laminate flooring, it should be removed for subfloor drying.
Oriented Strand Board (OSB)
OSB should be classified as a semi-porous material when making decisions about removal or replacement, considering the Category of water and time of exposure. When the moisture content of wood exceeds 16%, it is more susceptible to mold growth
Heat and Pressure Created Laminate Materials
This category includes materials that are often used as counter tops and hollow-core doors. These materials can absorb water and lose shape and strength; if so, they require replacement. If these materials retain their shape and strength, they should be treated as semi-porous materials.
Insulation can be made of shredded paper products that are chemically treated to reduce flammability. These chemicals can corrode metal parts in contact with the insulation. In a water intrusion, chemicals can leach out of cellulosic insulation, thereby changing its fire-retardant properties. In addition, water-saturated cellulosic insulation can compact and lose its R-value. Wet cellulose insulation should be removed, regardless of the Category of water, and replaced with new material after structural drying.
Open-cell foam can hold water and may need to be removed in order to dry other building components. Closed-cell foam does not readily absorb water and generally retains its~-value after a water intrusion. This insulation may be applied as rigid sheets, or by a spray method. Its main advantages are that it provides improved resistance to wind penetration in addition to uniform R-value. After having been wet, it does not lose its form or R-value when dried.
Coatings and paint films affect the permeability and absorption rates of materials. Therefore, drying strategies need to consider the effect that desorption and evaporation rates, created by coatings, have on affected materials.