Envelope Failures and Forensics

Sept. 24, 2013
Notice clues, identify evidence, and enlist investigators to solve the case.

When something goes wrong with building enclosures, the detective work is daunting. It will take heavy lifting to crack the case of cracking masonry, and if water is pooling at your window sill, the true culprit is just as slippery. To zoom in on the root cause of your problem, you’ll need more than a magnifying glass.

Proper identification depends on seeing the red flags, keeping up with general maintenance, and recruiting the right specialists, if necessary. Building envelope failures are insidious and pinning them down is far from elementary. But if you take the following steps, this sleuth work may uncover the whole truth.

Understand Performance Criteria
When the envelope fails, it’s important to have an understanding of how the system works so you can consider what could have gone wrong. A basic knowledge of components and properties can help you lay the necessary groundwork and map the crime scene.

“From a building enclosure perspective, there are five key performance points to consider, and each of those leads to specific failure paths,” explains Stéphane Hoffman, principal and facade engineering practice leader at engineering firm Morrison Hershfield.

Water management. The first goal of the envelope is to keep water out, whether that’s wind-driven rain or general moisture. Water can cause mold growth on insulation and corrode structural elements, among other disasters.

“The number one failure is water penetration, typically due to lack of maintenance as opposed to poor construction or design,” says James Cohen, principal at engineering firm Arup. “There are multiple barriers to stop water – literally thousands of feet of sealant at windows, joints, doors, and roofs. The likelihood that they are all correct is very low, so it’s usually not a single-item problem.”

Air leakage. The flow of conditioned air out of the building or of outside air through the envelope can lead to excessive heat loss and high energy bills.

“There is also potential for condensation if humidified interior air goes out or you’re pulling humid outdoor air inside,” adds Hoffman. “Additionally, air leakage can cause pressure differences and wind-driven rain can be sucked inside.”

Vapor diffusion. Although a little harder to understand, this property is as important as the others, because it also presents the possibility of condensation.

“Imagine two rooms side by side that have different humidity levels,” Hoffman explains. “Unless there is a vapor barrier between them, the two humidity levels will seek to equalize, and the interior wall cavity will suffer.”

Insulation. The insulation layer acts as the thermal barrier. Its aim is to prevent excessive exchange of heat from one environment to another.

“If insulation is damaged or missing, it can lead to occupant discomfort, draftiness, and temperature differences,” Hoffman says.

Differential movement. This term refers to outside factors like wind loading and also entail the thermal expansion and contraction of certain building materials, such as masonry or concrete.

“Your enclosure is all tied back to the base structure, and it has to accommodate for some movement between itself and the base structure,” Hoffman explains. “Differential movement can lead to breaches in one of the other four barriers and cause performance problems.”

Equipped with a basic understanding of envelope science, you’ll be able to take your knowledge into the field and dig into possible failures.PageBreak

Perform Periodic Inspections
Every so often – annually for certain components or monthly for others – you need to take the magnifying glass to the building exterior and interior to determine how your enclosure is performing.

Begin by paying attention to occupant complaints or asking them outright for their opinions via questionnaires, Cohen recommends.

“Is it dusty or humid in the occupied space? Are there hot or cold spots? Is it musty or smelly?” says Cohen. “Many times, the people who are living and working in the environment are your first source of clues.”

Look closely at finishes and fixtures indoors and out, Cohen says. Bubbling and staining will indicate poor water management. “If you see these issues, there’s a good chance the problem is more insidious,” he adds. “Don’t just think a dab of paint or bit of wallpaper will fix the root problem.”

It’s also helpful to look at spaces where no one usually goes. “Look in the ceiling space. Go into the attic, crawlspaces, basements, and cobwebby areas,” Cohen advises.

On an annual basis, inspect the general exterior of the building, paying close attention to sealants, flashings, and other water management components, says Daniel Lemieux, principal and unit manager at engineering firm Wiss, Janney, Elstner Associations, Inc.

“If there are any open joints, that’s a water entry path,” Lemieux says. “Those can lead to serious problems like mold growth or structural corrosion.”

The roof – a large component of the envelope on some buildings – should be inspected every six months or at seasonal changes, Cohen advises. “Look at the penetrations of pipes and equipment. See if any seams are opening or lifting. Make sure water isn’t collecting anywhere and is draining properly – check for clogged drains more than twice a year,” he says. “Roof problems manifest themselves in facades and even basements, so be sure to get up there and check them out.”

Some of these failures can be difficult to identify for facilities managers who don’t have much experience with enclosures, says Lance LeTellier, managing principal with firm Criterium-LeTellier Engineers.

“If the problem starts getting technical in nature or if they can’t figure out the true cause on their own, it’s probably best to get some outside help,” he says.

Keep Up with Routine Maintenance
“Mitigation is always far less costly in every sense of that word – money, time, and inconvenience – than repair,” Cohen stresses. “A lack of regular maintenance comes from a lack of regular inspections. To only perform maintenance in response to a problem means that problem was allowed to occur. Response is not the answer – mitigation is the answer.”

Have a routine maintenance schedule in place, Lemieux recommends. That entails keeping track of the service life of all components – from roofing and cladding systems down to sealants and gaskets. “If you get close to the anticipated service life, change it,” he says. “Don’t allow deferred maintenance to occur. Minor issues can turn into severe problems if you defer these responsibilities to someone else.”

Document the findings of the inspections and keep them on file so you can crack the case if a more serious problem pops up.

“When it comes to involving a professional, having a good picture of how the performance has been, how often issues are occurring, and how they were identified is important,” Hoffman says. “Keep the as-built documents if you have them. Log maintenance items such as when the roof was last replaced or when the windows were changed out.”

Taking care of the building is similar to the general upkeep of your car, Hoffman adds. “Getting your oil changed is like checking sealants or cleaning the roof,” he says. “Then every so often you need to plan for bigger things like reroofing or changing your tires.”

Neglect will cost you and planning is crucial. Proactive owners and facility managers should have a capital plan and know what the building’s needs and priorities are.

“Some owners don’t have a sense of what they have and how long it will last, and then they eventually have a breakdown because they’re operating the building past the service life of its components,” Hoffman says. “You don’t want to pour money into a system that has reached the end of its life. You have to realize when you can do a targeted repair to extend service life or when it’s time to just replace something. Maintenance and renewal plans are key for that.”PageBreak

Solve with Proper Remedies
Wrapping the case up and filing it away depends on implementing the right solution. Beware of just going to a general contractor right off the bat.

“If you have some water staining or leaks, it’s easy to call a restoration guy to come out and start working on the skin,” Lemieux says. “But it’s very important to do the investigation and get the right diagnosis before you move into repair. There has been good money thrown at a solution only to have the leaks reappear afterwards.”

The remedy in some instances might be as simple as replacing some sealants and flashings and bolstering your initial barrier. Other times remediation can be more drastic and entail recladding or replacing insulation layers. Structural corrosion might require installing supplementary anchors.

The extreme nature of these repairs should be clues that acting proactively is the best policy.

“What might have been a relatively small cost at first may now involve removing interior drywall, dealing with corroded fasteners and components inside the wall cavity, and moisture remediation,” says Lemieux. “The level of repair and how far you have to peel the onion to find the problem becomes much more extensive. Don’t let things balloon to a point where they never should have gotten.”

Exterior Clues Indicating Facade Failure
Application of stucco hid and exacerbated deteriorating mortar. In fact, the remaining stucco layer could easily be removed by hand, revealing the damaged masonry underneath.

Sealants need to inspected regularly and maintained or replaced as needed. Measure the sealant to see if it’s cracking as the building expands and contracts over time.

The unprotected steel lintel above an air conditioning unit has rusted and expanded, lifting the wall and cracking the masonry. The cracks and openings present paths for moisture.

Compression failures may indicate a significant structural issue.


INTERIOR Clues Indicating Facade Failure 
Interior damage is often the earliest and easiest method of detecting facade issues. The cracking, blistering, and mold are indicative of a particularly invasive and insidious problem.

Even issues like mold on the ceiling, which seem minor, may reveal much more significant water penetration issues with either the facade or roof. Don’t neglect these red flags.

This mold found behind a cabinet was the first sign of moisture penetrating from the exterior. Sometimes your investigation will require looking in places that are usually hidden.


Roofing Clues Indicating Facade Failure 
An aging roof that starts to crack at the laps, flashing, and seams is often failing or reaching the end of its service life. Enlist a specialist if you don’t have staff to inspect the roof.

Problems at the roof and eaves are often the precursor to failures on the facade. Even issues that seem minor, such as peeling and blistering, should not be ignored.

Standing water is always a concern. Here, it indicates that the drain is no longer the low point on this roof or that it could be clogged. Inspect roof drains at least once per year.

Chris Curtland [email protected] is assistant editor of BUILDINGS.

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