A correctly installed, retrofitted façade produces an enhanced look and upgraded operations
With building energy efficiency becoming more vital to the construction industry, retrofitting existing building façades has grown in importance and popularity. Tearing down old, inefficient buildings and replacing them with new high-performance ones may not be affordable or practical. Correctly installed, a retrofitted façade can produce comfort conditions in a building with less energy expenditure, while enhancing the building with a whole new clean aesthetically pleasing look.
John Priebe, architectural representative at Tubelite Inc., Walker, Mich., believes metal buildings’ exterior configurations can be transformed and retrofitted by removing sections of the siding to create new or larger openings that can be filled with windows, storefronts and curtainwalls. “The creation of new openings allows for additional daylighting for an open space environment and a new appearance to a building’s façade,” he says.
For example, a dramatic retrofitted façade and an adaptive reuse design transformed a vacant Walmart into the new McAllen, Texas, Public Library. The former “big box” building’s appearance drastically has been altered with dramatic exterior features, including a 108- by 44-foot main-entry canopy, clad in Alucobond aluminum composite material by Statesville, N.C.-based 3A Composites USA Inc. Also, the $20-million, 74,000-square-foot, three-story, long-frame, Boston-based Carpenters Center building received a retrofitted façade to successfully transform it from a former two-story laundry facility. This was accomplished via a mix of materials, including traditional wood and glass, as well as Alucobond aluminum composite material installed as exterior cladding.
What follows are some basic installation considerations and instructions to ensure a building’s exterior configuration is retrofitted right.
Metal versus nonmetal buildings
What are some of the main installation differences between façade retrofit on a metal building versus a nonmetal building? “Metal buildings have trims and flashings that are used to create openings in the metal siding and may be tied into the window frames,” says Priebe. “Removing existing windows may require removal or disturb these trims and flashings. It is important to ensure they are replaced properly to ensure there are no air or water leaks maintaining the building envelope. Nonmetal buildings use the wall construction components to create the openings and the windows are typically independent. Removal and replacement do not cause as much disruption to the perimeter conditions.”
Most metal building façades are non-load bearing without exterior columns, but a nonmetal building may have additional columns and beams that must be evaluated during the construction. “Nonmetal building structures with flat roofs may have the roof tied to the façade which may create a leak hazard at this condition,” says Don Riggs, assistant general manager/project service at MBCI, Houston. “A metal building roof is normally independent of the façade system.”
A metal building may have girt spacing designed specifically to the original cladding material. “A new system may require different spacing for the cladding attachment and this would need to be evaluated,” says Dan Vinet, PE, sales director, Kalzip Inc., Valparaiso, Ind. “A non-metal building (masonry, brick) may have issues with the straightness of the walls and require furring to level the surface in advance of the metal cladding installation.”
Retrofit pre-installation
Retrofitting a building façade requires careful planning, conscientious attention to details and suitable working conditions. As with any factoryfinished product, a curtainwall-a common retrofit component-must be handled with experienced care and protected from damage if it is to function as intended. “With proper skills, due attention to the logical division of responsibilities and common-sense precautions, its installation becomes a rapid and relatively simple process,” says Dean Lewis, education and technical information manager, American Architectural Manufacturers Association (AAMA), Schaumburg, Ill. “Long experience has proven that, even under adverse conditions, the aluminum curtainwall, however complex its design, can be completed in much less time than is needed to build conventional masonry walls.”
Structural, insulation and moisture control considerations, along with the accessibility of the wall must be evaluated and the appropriate method for installation selected (swing stage, scaffold, etc.) prior to the façade retrofit. “The logistics, access and duration of the work will also need to be taken into account when evaluating the wall to be retrofitted,” says Vinet.
One potential pre-installation step in some façade retrofits is determining if the existing cladding material can be left in place or if it needs to be dismantled. “If dismantled, then the existing subframing system would have to be evaluated for adequacy to accept the new cladding system loads and attachment requirements,” says Vinet. “If it does not need to be dismantled, then the existing wall should be evaluated for flatness. Additional furring members may need to be introduced if the existing wall is out of plumb. After the furring or intermediate sub-framing is placed then optional additional insulation could be added. Then finally the metal façade installed.” Riggs believes the following questions must be asked prior to a retrofit façade installation:
• Why is a retrofit necessary?
• Repair of water infiltration?
• Update to energy codes or increase energy efficiency?
• Storm or fire damage?
• Aesthetics such as changing the image of the structure?
• Change in ownership of the building requiring new signage or a corporate design?
Riggs stresses that contractors should adhere to the following procedures to prepare a building prior to retrofitting a building façade:
• Similar to roofing retrofit, have the existing structure evaluated by an engineer to see that the structure can support the new façade, and if not, what is necessary to make it capable of accepting the new loads.
• Evaluate the condition of the existing framing and locate any plumbing, HVAC or electrical issues.
• See that the existing framing meets current building codes.
• If new signage is involved will the new plan meet current sign ordinance?
Retrofit façade installation steps
Retrofitting a building façade must be done in accordance with the local current building code and applicable standards. These could include IBC, MBMA, AAMA, AISI, ASCE and AISC standards and guidelines.
“The construction industry is governed by a group of regulations and requirements,” says Lewis. “These rules and regulations are designed to provide uniformity on minimum design and construction practices, thereby avoiding inconsistencies arising from differing approaches of architects, builders and installers. Once national, state or local codes are adopted by jurisdictions, they become law and must be followed. Both, AAMA IPCB-08, Standard Practice for the Installation of Windows and Doors in Commercial Buildings, and AAMA CWG-1-89, Installation of Aluminum Curtain Walls, provide step-by-step instructions on proper installation procedures for commercial buildings.”
Riggs believes façade retrofit installation can be summarized by the following procedures:
• Secure the proper building permits.
• Barricade areas to provide safety to building occupants and the public.
• Demolish the existing coverings and framing as required. Be especially careful of hazardous material such as asbestos. Make sure electricians, HVAC techs and plumbers are available to handle any of these systems should they interfere with the demolition.
• Once demolition is complete provide for temporary covering or walls to provide weather and security protection.
• If required replace or add framing as required by the engineering and building codes. Attempt to square the existing framing which may require extensive shimming or jacking.
• Install any new thermal barriers and rough in any electrical connections.
• Apply the new finish materials, such as metal panels or aluminum composite panels.
Retrofit does windows
Windows are a common component of buildings façades. Priebe believes façade retrofit installation emphasizing windows can be summarized by the following procedures:
• Field verification of openings for proper sizing of new window frames. Field verification should confirm the condition of the framed opening will support the anchoring required, existing closures and trims at openings for potential modifications or replacements. Frame depth and interior conditions also should be reviewed to ensure replacement windows will work with the existing surroundings.
• Removal of the existing windows is dependent on the anchoring. The windows could be anchored by exterior fin (“nail fin”), through the jamb, with an interior “strap” or clip. The removal of the windows may require the exterior trim be removed if overlapped onto the window.
• Existing perimeter conditions should be evaluated after the removal to ensure structural integrity to support new windows and anchors (calculated). New or existing trim/ flashing, including the new window system sill, should be installed from siding-to-opening structure conditions to provide a clean, rough opening to accept new windows.
• Installation of the new windows per manufacturers’ instructions and engineers review for anchoring to meet codes. Anchoring that requires interior strap or clip anchors should follow the same procedure as through-frame anchoring, except that the interior conditions will need to be disturbed and refinished. Fin anchoring for new windows may require a more extensive removal of the exterior trim and siding, and may not be the best application for replacements.
• Clean off existing and reused flashing to accept perimeter sealants. Residue from old caulking may not provide proper adhesion causing water and air penetration. Perimeter sealants should be installed per manufacturers’ instructions, including joint size, preparation and backer rods. Attention should be made to the siding and trims to verify that they are airtight and watertight as they may be disturbed during the replacement of the windows.
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Ask the Engineers
Metal Construction News asked four engineers-William Bast, Eric Wheeler, Dziugas Reneckis and Andrew Rixon-at Chicago-based Thornton Tomasetti to describe in their own words how to better understand a metal building façade retrofit:
One of the most important items to be determined prior to retrofitting a metal building façade is to understand the condition of the existing structural system. For example, the following questions should be asked:
• Is it safe to assume the original structure was erected to AISC tolerances? Construction, erection and fabrication tolerances are very important considerations in the retrofit, and the connection details must accommodate these tolerances.
• If or where is it possible to connect new members to the existing structure? Must the connections be made at the columns, or could they be made at the spandrels or slabs?
• Can the existing foundation take the loads from the new façade?
• If there are concrete-encased members, will the concrete need to be removed?
• What utilities may be in the way of the new connections?
• Do any hazardous materials, such as asbestos or lead-based paint, need to be remediated?
• Can the existing cladding/windows remain, or must they be removed?
• Will the building be occupied fully or partly during the construction process?
Once the existing structure’s condition is determined, then the option to over-clad or re-clad the building needs to be discussed; then the design process can begin. There are many more aspects to investigate an existing structure to ensure that retrofitting the façade is performed safely, and effectively. Each project presents its own unique aspects; therefore, there is not a simple step-by-step procedure of how to retrofit a façade. An extensive investigation into the existing building must be completed, and the different analysis and construction methods will need to be reviewed to determine the most effective way to design and construct the project.
