From energy efficiency to indoor air quality, the issues that face today's building owners are increasingly complex. While there is no substitute for getting a design professional involved in diagnosing and fixing a problem in a structure, understanding the exterior components - or the building envelope - will pay dividends in determining the optimal solution.
A key ingredient to this approach is a thorough review of the essential components of the building envelope - walls, roof, foundations, windows, etc. By examining the way the exterior of a building was designed and constructed, as well as the repairs that have been made during its lifetime, you can help pinpoint the source of the problem.
The Breakdown
Of the components that make up the building envelope, perhaps the most important when determining the source of a problem is the wall system. In order for a wall system to function as intended, several factors must be taken into consideration. These include the selection and design of compatible materials and systems, proper detailing of material junctions and terminations, installation and inspection of these details during construction, the ability of composite envelope systems to function during weather cycles and proper maintenance.
The slightest difference between design intent and the way a wall system was constructed can have a major impact on performance. The amount of detailing shown on drawings does not always provide sufficient instruction regarding how to detail intersections, terminations and penetrations of wall systems. Such gaps cause field personnel to make an educated guess.
This scenario is especially true in the construction of cavity walls where there is zero tolerance for error in the design/construction. In most circumstances, any design or field detailing error will result in water infiltration or even more serious failures as a result of the infiltration.
The wall system design can be that of a barrier or a water-managed wall, though a wall system may have characteristics of both. Barrier walls use a blocking or interrupting mechanism to prevent the movement of water to the interior of the building. Mass barrier walls, such as those constructed of multi-wythe masonry and stone, rely on sufficient thickness and mass to prevent water infiltration.
In contrast, face-sealed barrier walls, which are often constructed of precast concrete, stone, EIFS and certain metal panels, depend on the exposed exterior wall surface to prevent water infiltration. With face-sealed barrier walls, it is imperative that all joints and interfaces be sealed to provide this exterior barrier.
Whereas barrier walls are designed to keep out water entirely, water-managed walls allow for the control and discharge of anticipated amounts of water that penetrate the exterior surfaces. Drainage walls incorporate a cavity that catches water and directs it toward a flashing or drainage system where it is flushed to the exterior. When constructing drainage walls, special care must be taken to avoid bridging the interior and exterior wall.
Maintain Control
Collection and retention walls control water leaks and damage by systematically collecting water that penetrates the exterior surface of the wall, allowing minor amounts of water to accumulate in cavity dams and reservoirs. The water is then redirected to weep holes or other drainage mechanisms, or is allowed to dissipate. Rain screen/pressure equalization walls reduce the air pressure differentials across the exterior surface of a wall, thereby reducing the amount of wind-driven water that comes into contact with the walls.
With any type of wall system, the key to long-term performance is a regular maintenance program that is designed with the life cycle of specific building components in mind. Exterior seals, sealants and waterproofing membranes used in contemporary design should be given particular attention.
Proactive maintenance should encompass an annual maintenance budget, regular building condition assessments, annual proactive maintenance and seasonal visual inspections. Visual seasonal inspections should include checking drains, gutters and downspouts as well as using a pair of binoculars to review the structure. In areas of seasonal change and freeze-thaw cycles, it is important to perform these inspections after every major weather event.
In addition to planned maintenance repair work, capital renewal funding should be set aside for existing structures separately from new construction. Occasionally, proactive maintenance isn't enough to prevent damage and reactive maintenance is necessary.
Gagging Leaks
One of the most common problems for which reactive maintenance is required is water leakage - water penetrating the outer surfaces of the building. Interestingly, as much as 90% of all water intrusion problems occur within 1% of the total exterior surface area of the building.
When investigating a leak, the team should review project documents to determine the intended design of the building; evaluate drawings in order to understand the wall system application and how the building was intended to manage water/moisture; determine the building's service history; perform a visual inspection; and perform an investigative test to recreate leakage and water paths under controlled conditions. This information, coupled with guidance from a design/construction professional, will result in realistic repair approaches.
Armed with building envelope knowledge, of the wall system in particular, building owners have the opportunity to avoid quick-fix solutions and instead implement long-term solutions that will likely save money and time. The end result of following these steps is a more efficient, durable and cost-effective facility for everyone to enjoy for years to come.