The Meaning of This Intrusion
Consequence of leakageWater leakage at the interior of the facility does more than infuriate building occupants. There are several other consequences. A primary issue is consequential damage to the interior finishes (drywall, paint, etc.) and furnishings, usually by moisture infiltration.
Persistent water stains contribute to mold and mildew growth, which typically forms on interior materials through long-term exposure. Moisture infiltration at insulated cavity walls will decrease the insulation's thermal and structural integrity. Insulation-once wet-never completely dries out. The loss of insulating value will result in higher energy costs.
Moisture infiltration will also cause material deterioration of all exterior and interior materials that it passes through. Wood rot is a common occurrence from continual moisture exposed to interior grade wood. Steel products, such as metal studs and anchors, experience rust and corrosion when they come in contact with moisture over infinite durations. Exposure to moisture contributes to spalling and cracking of concrete, lightweight concrete and stucco materials. There is also the possibility of electrical damage if infiltrating water penetrates a circuit and leads to electrical shorts or corrosion.
Design to eliminateThe two most common types of exterior wall construction employed at this time are barrier wall construction and cavity wall construction. Each of these methods has design issues that lead to moisture infiltration. Through the identification of these issues proper solutions can be presented to eliminate moisture infiltration.
Contemporary barrier walls are now designed and constructed in contrast to traditional barrier walls, which employed water penetration limitations in the design. The traditional barrier walls were constructed in mass, which allowed for the gradual absorption and evaporation of the moisture. Contemporary walls have little mass and moisture absorption is rapid, which could lead to penetration.
The traditional barrier walls also employed physical shielding components in the initial design. Shielding components, such as roof overhangs, set backs of wall windows and drip edges, were all constructed to protect the vulnerable building joints from water exposure.
Many contemporary barrier walls do not have those shielding components and rely on selected materials for water penetration resistance. This thought process relies solely on the capacity of a material, which may or may not be designed to accommodate certain tolerances. In most cases, there is unrealistic reliance on a material's true capacity and capabilities.
For instance, it has become common for the use of impermeable cladding materials to be constructed at exterior barrier walls. These products are functional until (inevitable) surface cracks develop. Water absorption occurs at these points, prompting further determination of the wall and probable openings for moisture infiltration. There is also some confusion regarding true impermeable surfaces. For the record, stucco, masonry and concrete cladding materials are not impermeable and rarely go uncracked. These types of materials are susceptible to surface cracks from stress concentration-such as at reentrant corners of windows and doors-and are due to normal structural deflections from thermal movement and shrinkage. If these types of products are installed, proper long-term waterproofing solutions must be provided.
In recent times, there has also been a sufficient reliance placed on permanently sealed joints with exterior sealant materials. These types of products have waterproofing limitations and there are drawbacks to their use as true protective components. The first drawback is that there is no redundancy. A failure at this point allows for the free flow of moisture into the building. They do not provide highly reliable and durable water proofing protection because they have relatively short service lives, typically three to five years. The duration of the life span is reduced due to heat aging, UV resistant and stress/strain cracks. Proper application is also a concern, due to the fact that the applied substrate must be properly prepared. Minimal contamination decreases adhesion. The substrate must be primed (if required) and the ground clean.
Moisture infiltration at exterior walls can be eliminated by employing proper pre-design strategies that do not rely solely on material performance (particularly, materials that are not designed to provide long-term weatherproofing protection). Exterior contractors can aid designers by pointing out vulnerable points in exterior design and by recommending proven techniques and application methods that can reduce moisture infiltration.