Considerations for Perforated Metal Applications

By Jordan Scott

Demand for perforated metal products on facades is increasing nationwide, as architects see its potential for sunshading and adding an aesthetic element to applications
such as parking garages. Gary Davis, A. Zahner Co. director of marketing, says  he’s seen sales of perforated metal double in the past year at his Kansas City, Mo.-based company. With perforated metal trending, architects and glazing contractors need to be aware of several considerations to navigate specification and installation successfully.

Aluminum vs. Steel

Petersen Aluminum Corp. (PAC), based in Elk Grove Village, Ill., always recommends using aluminum rather than steel for exterior applications due to the possibility of weather causing exposed steel to erode. Rob Heselbarth, PAC director of communications, says that some coatings manufacturers such as Sherwin-Williams Coil Coatings, which makes the company’s PAC-CLAD paint, won’t warranty their paint on perforated steel.

“We will perforate steel if it’s being used for interior applications because there is no concern about exposure to weather,” adds Dave Landis, manager of technical services and field inspections for the Southeastern region at Petersen, who points out that the cut edges on the holes of the perforated sheet are where erosion will occur.

These edges are not usually painted or finished, nor is the side of the perforated metal facing the building. Heselbarth says, however, that Petersen can perforate mill-finished aluminum for painting that will include paint on the inside edges of the holes and both sides of the metal sheet.

“This is often requested for parking garage partitions,” he says.

Scott Hollingsworth, business development manager at California Sheet Metal in El Cajon, Calif., adds that aluminum loves to be fabricated, making it an accepted exterior material.

“We can get a 20- to 30-year warranty on the paint finish with aluminum,” he says, adding that aluminum is also lightweight and the support required is less drastic than some heavier façade materials. For interior applications his company might change the finish from Kynar to a powder coating.

Zahner’s Davis says he’s seen more architects move toward copper, bronze, blackened steel and weathered steel.

“They’re using very natural metals to create a building that has a bit of robustness,” he says, noting that these metals don’t stay static over time, instead changing with time and weather. However, these metals can often be value engineered out of a project.

There are also certain parameters that preclude the use of some metals in certain locations. It’s also a matter of longevity, adds Davis, who points out that if an owner or developer wants the project to last for 50 years then his company will push toward copper and stainless steel, and away from painted surfaces which he says will need to be
redone in 20 years.

Perforation Trends

Landis has noticed that the use of lighting or signage behind perforated metal to create an enhanced visual effect is a trend. In the case of the Everest Charter School project in Chicago, an image of school children was applied to the wall behind the perforated panels. “This has sparked interest with architects because they’re able to create brand identification on their building rather than using mundane signage,” he says.

Perforated metal isn’t used solely for aesthetic enhancement; in some cases it can be used to provide solar shading on a west- or south-facing façade. Panels in front of glass also become backlit naturally due to the lite escaping through the glazing, says Davis.

Considerations

Perforated aluminum can be painted with a variety of colors thanks to Kynar finishes, according to Hollingsworth. “We see an awful lot of silver metallic but there’s a wide variety of modern colors being used,” he says.

There are limitations when it comes to the amount of perforation that is practical, according to Landis. He says that when specifying perforated metal that will be roll formed as a single skin architects need to know that there’s a limitation of only 51% allowable open area on the panels.

“If you get beyond that most manufactures can’t roll form a panel,” he says. “Generally, we start at around 14% open area and go as large as 51% in different hole sizes and patterns.”

Hollingsworth adds that if the perforation panels are large they might require a stiffener, or an extrusion behind the panel used to keep it flat, though this can block the perforations’ see-through ability.

“The solution is to hide it behind an image, otherwise go for a more reasonably-sized panel that can survive the deflection criteria without stiffening,” he says.

Installation Concerns

Landis suggests glazing contractors keep in mind that the lead time for perforated metal products can be around eight to 12 weeks depending on different factors.

“This isn’t a big deal as long as everyone plans on it,” he says, adding that the higher lead time is because the variety of options with perforated metal makes it difficult to keep it stocked.

While the lead times for perforated metal might take longer than a solid sheet of metal, Landis says the installation requires the same process, schedule, fasteners and flashing details. Hollingsworth agrees, adding that there is usually a natural point in the construction process when the panels should be installed since the perforated metal is often installed over glass, concrete or a weather barrier.

However, Heselbarth recommends that glaziers degrease the metal following perforation because it will be saturated with lubricant from the perforation process.

Davis says that it’s important to coordinate, as Zahner integrates its panels with the curtainwall, window wall or post tension slabs.

“If the curtainwall is being unitized, the best way for us to work with the curtainwall people is to work concurrently so the panels are installed flat before they’re hoisted in the air,” he says, “so when the unitized curtainwall goes up it has the panels attached.”

The key for the successful installation of perforated metal panels, he says, is communication between all parties involved.

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