Faults and failures in the outer skin of a building could be a disaster waiting to happen
GREATER METROPLEX -- It doesn't always take a tornado to make the walls come tumbling down. Inadequate materials, poor installation, improper maintenance schedules, extreme heat and budget cuts can all contribute to problems with curtain walls.
"You have to maintain those curtain walls today in order to avoid spending a lot more in the future, because decay is exponential, not linear. A $50,000 repair today might cost you $200,000 in a couple of years and $1 million in four," said Joe Solinski, president of Stone & Glazing Consulting, an exterior-wall consulting-services firm.
Curtain wall is the name given to the non-load bearing, exterior vertical skin of a building that typically includes materials such as glass, stone, aluminum, marble, metal or composite panels, sealants or brick. In addition to preventing water entry and air leakage, curtain walls allow light to enter windows, help define a building's character and protect its interior.
But when things go wrong there is no telling what might happen -- anything from tiny pieces of glass falling from a high-rise to a huge chunk of stone tumbling from a skyscraper. "A curtain wall's long-term behavior is a function both of its components and its response to weather-element exposure," said Dudley McFarquhar, associate director of the curtain wall sector for LZA Technology in Dallas. LZA provides investigative engineering, design and construction-materials evaluation.
A combination of undersized or poorly installed materials or connections combined with wind cycling, temperature cycling -- heat-freeze-thaw cycles -- coupled with water entry can all contribute to degradation of materials or their joinery, McFarquhar said.
"Some curtain walls have problems either with the design or installation of the waterproofing," he said. "Situations such as poor flashing details allow uncontrolled water infiltration. This can result in damage to walls such as sheet rock-fastener corrosion or loosening of mortar joints. Issues with freeze-thaw cycles could cause flaking of some stone panel types. In general, over time, if not maintained, parts of the building could become loose and fall."
Unlike older cities like New York and Chicago, Dallas does not have a façade-inspection ordinance that mandates regular building inspections. While building codes generally prescribe design-loading requirements, they usually don't take building deterioration into account. That makes it especially critical for the building ownership or property-management company to implement a regular schedule of inspection and maintenance to correct potential problems before they happen.
Curtain-wall problems can occur as a result of product failure, poor installation, design problems -- or all three. "The challenge of building veneers is architects want their buildings to look like no other building, so they often create all sorts of marriages of brick, stone and glass to make the aesthetic match their visualization," said Solinski. "Then you add suppliers to that mix -- who may be using materials that have not been tested over time in those situations -- and installers who can take a perfectly good product and do a poor job of installing it."
Another issue arises when specifications for the building's design are not properly reviewed and enforced. When the wrong materials are used and budgets are tight, even heat and sun can cause problems.
"The architect may have done his job up front specifying certain product or performance criteria, but it can be sacrificed due to budget," said Mike Harvey, architectural sales representative from Wausau Windows, a curtain wall systems and aluminum-window manufacturer and installer.
"If an owner wants a $2 million design with a $1 million budget, the general contractor may step in and start cutting costs. But when quality is sacrificed, tragedy can strike," he said.
"Let's say you have a shadow cutting across a piece of glass on a southern exposure of a glass-covered building, where temperatures can reach 160-180 degrees," Harvey said. "If the subcontractor has provided cheaper glass that is not properly heat-strengthened or tempered, it can fracture under that kind of stress."
Problems also result when the pressure is on and deadlines are moved up. "The industry has always been budget and schedule driven, but now management has computers, e-mail, software -- information on the fly -- while the guy in the field is pretty much still out there with the hammer and the nail," Solinski said. "If he can't finish the job quickly enough, he may start skipping steps."
Because every building is a unique mix of materials, each requires its own customized schedule, said John Dawson, director of engineering with Trizec Hahn in Dallas. "Accidents can still happen, but you can avoid most major problems with the right inspection schedule by qualified people and by budgeting for maintenance costs ahead of time. Even granite, which typically doesn't deteriorate, can be a problem if it is secured improperly."
Thin stone veneers, which have grown rapidly in popularity in the building trade since the 1960s, often present special problems. Because technological advances now allow designers to specify thinner, lighter stone panels, installation quality control and adherence to details is even more critical, according to Solinski.
"If there's a problem, some people will have a tendency to talk themselves out of it by sweeping it under the rug. But they always pay for it later -- in a lawsuit, higher repair costs or loss of tenants," he said.t- and schedule-driven, but now management all has computers, email, software -- information on the fly -- while the guy in the field is pretty much still out there with the hammer and the nail. If he can't finish the job quickly enough, he may start skipping steps," Solinski said.
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