The Building Envelope: A Guide To Determining Problems
- By Ellen Kollie
- November 1st, 2014
PHOTO COURTESY S. CARTER
Facility Managers need their building envelopes, as a top priority, to be watertight, safe and energy efficient,” says Scott R. Whitaker, president and CEO of Portland, ME-based Building Envelope Specialists Inc., which provides such services as forensic investigation, repair documents and specifications, and mortar testing and analysis. “The envelopes must create shells around buildings that function as intended and age as expected.”
To keep a building envelope (walls, windows, roof, waterproofing and structure) functioning as intended, sometimes an investigation and evaluation is required to define problems, which, once discovered and resolved, extend a building’s service life. The following is a guide for determining building envelope problems.
KNOW THE BUILDING’S HISTORY
“The more you know about the building’s history before you begin the investigation, the less intrusive the evaluation will be,” says Edward J. Stewart, RRC, senior associate of Weymouth, MA-based Gale Associates, Inc., which specializes in the repair, renovation and adaptive reuse of existing buildings.
Stewart recommends having the original design and construction documents, as well as a history of repairs and renovations, which reduces invasive testing and also ensures that future repairs and renovations are made with products the same as or as close to the original as possible to ensure the same performance characteristics.
“Compiling these documents gives you a solid understanding of the as-built construction and tells where there may be potential problems,” Stewart says. “It’s not always possible, though. That’s when it becomes a guessing game as to what the underlying conditions are.”
PERFORM A FIELD INSPECTION
A field inspection is an examination of existing conditions, and it is one of the most important aspects of evaluating a building envelope. There are several levels to a field inspection.
The first is an inside look at known leak locations. Many buildings are large, which, from a cost-effectiveness standpoint, prohibits an evaluation of every square foot. An inside look at known leaks begins to tell the story. For example, water leakage at the bottom sill level of a window may indicate a flashing issue. Water leakage at the ceiling may indicate a wall or roof issue. “Now, by knowing the different leak locations inside the building, you can then focus on specific problem areas on the exterior of the building,” says Stewart. “You’re extrapolating out.”
The second level of a field inspection is a visual inspection of the envelope’s exterior from the ground level. It may require the use of a pair of high-powered binoculars. “This gives a picture of how the building is performing and potential problems, such as masonry displacement, cracks, spalls, etc.,” says Edwards. “You’re looking for potential safety issues associated with façade materials falling off and injuring pedestrians.”
The third level is a close “hands-on” inspection, using a man lift to inspect potential defective conditions noted during the binocular survey; issues such as a displaced cornice, which would typically be a symptom of an underlying issue. Symptoms themselves strike a nerve with Edwards. “Too often it happens that building owners address the visual deficiency without determining the cause of said symptoms,” he explains. “For instance, if granite panel (often six-foot by eight-foot pieces) is cracked on all the corners, a fix may be fill the cracks by grout injection. That treats the symptom, but not the underlying problem, which may be that the anchors have rusted and are expanding against the stone, cracking it, and leaving it unanchored to the building.”
CONDUCT FIELD TESTING
Field testing, if required, is done to correlate paths of moisture infiltration with observed damages. Recreating the leakage in a controlled manner is a reliable way to test for moisture. There are numerous types of tests that fall under three categories: nondestructive, destructive and laboratory. Here’s a brief look at each.
Nondestructive: “With nondestructive testing,” Stewart says, “you’re reviewing for problems without cutting into the building.” A number of different tests fall in the nondestructive category. A common one is infrared thermography, which photographs the building exterior and reveals wet components, such as insulation and sheathing. Another is a water spray test, which simulates wind-driven rain. Using a garden hose with a calibrated nozzle attached, water is directed to a specific defect. Following the water’s path indicates how moisture is penetrating into the building. A third nondestructive test is ground penetrating radar (GPR), which is designed for façades where wall systems are displaced from the building. It uses an electromagnetic pulse to determine the location of reinforcement within the walls, such as the spacing and size of rebar or anchors.
Destructive: “When it comes to destructive testing,” says Stewart, “you’re opening up specific areas of the building façade in order to get a good look at concealed underlying conditions. Common methods are test cuts and borings. Remember, simply replacing cracked brick doesn’t address what caused it to crack in the first place. Steel may be corroded and resultant exfoliation (rusting) can push the wall out (rust jacking), or there may not be enough anchors or fasteners.”
Destructive testing also allows you to collect samples for laboratory testing. For example, samples of coatings and painted finishes can be used to determine the presence of lead or asbestos. Similarly, masonry or concrete samples can be tested to identify the mode of deterioration and/or composition of said components.
Laboratory testing: The purpose of laboratory testing is to get a better idea of existing material types, and it can provide information concerning proper surface preparation, material selection and implementation of repairs. Common tests include hazardous materials, such as lead and asbestos; petrographic, which tells how the concrete is performing; and mortar analysis, which tells the composition and formulation of mortar.
CONDUCT AN ENGINEERING ANALYSIS
Armed with original documentation and service history, as well as information gleaned from the field inspection and laboratory results, it’s time to conduct a comprehensive engineering analysis. It should include an assessment of field and laboratory data and structural analysis. It should also include, but not be limited to, the following thermal analysis, fire rating requirements and cost estimates.
Repair considerations should include three things: the effect the repairs may have on the building and its operations; ensuring appropriate preparation of surfaces to be repaired, and providing chemical and mechanical bonds for new materials; and, when choosing materials, an understanding of their performance limitations.
THE FINAL REPORT
If you’re using a professional to determine problems with your building envelope, this person will prepare for you a final report of all the above steps. If you’re doing the evaluation yourself, consider preparing a final report. Clear and concise documentation of the evaluation, problems and needs serves as a tool to assist with funding requests. “The final report tells a story,” says Stewart. “It has to be sufficiently technical in nature to reduce liability exposure yet clearly written and understandable by non-engineers, such as financial personnel responsible for allotting funds for repairs.”
As an example, a report summary from 2009, where Stewart was asked to conduct an evaluation of the exterior masonry and associated flashing components of a campus facility, is structured as such: executive summary, purpose and scope, background, leak audit, relative humidity and temperature readings, field observations, test cuts, controlled leak testing, laboratory testing, discussions and recommendations, conclusions, preliminary budget estimates. The report also includes photographic documentation of deficiencies.
Ultimately, a thorough building envelope evaluation results in long-term cost savings in that it allows you to make repairs, prioritizing them in order of importance and according to your budget, so that you once again have a building that is watertight, safe and energy efficient. “It’s about being proactive as opposed to reactive,” adds Whitaker. “Do an evaluation before problems occur to stay ahead of them.”
IT’S A PIECE OF CAKE
Components of a building envelope include the roof, which provides a weather-tight skin; walls that create a rain and heat/cold shield; windows that allow the sun to come in and the rain to stay out; and a foundation that keeps frost and water out.
Which component is most important? “It’s like making a cake,” explains Whitaker. “When making a cake, which ingredient is most important? The eggs? The sugar? The flour? They’re equally important. If one ingredient is missing, you can’t eat the cake. It’s the same with the building envelope. If one component is missing, you don’t have a building envelope that is watertight, safe and energy efficient. You have a facility that isn’t useable.
“Similarly,” Whitaker continues, “for a cake to taste its best, it must be made with fresh ingredients. If your baking soda is expired, you replace it with new so you have a dessert worthy to serve your guests. For a building envelope to function at its best, the components must be well maintained. If the windows are leaking, you replace them. This gives you a building that serves its occupants as designed and intended.”
This article originally appeared in the November 2014 issue of College Planning & Management.