Case Study: 511 Marigny Historic Steel Window Restoration

At the southern tip of the Marigny Triangle, close to the Mississippi River, stands a three-story brick structure that once anchored the Alden Mills hosiery factory. Founded in 1891, the operation quickly grew to become one of the largest knitting mills in the South. The main “shoebox”-shaped mill building along Decatur Street, was constructed in 1895; the “hatbox”-shaped addition fronting on Marigny Street dates from 1916. By the end of WWI, the factory employed approximately 450 people and produced nearly 2,500 pairs of hosier per day.[1] While Alden Mills closed in the mid-1950s, most of the buildings in the complex were subsequently used as warehouse and office space by a variety of other businesses, most notably the Godchaux department store.

Like so many early twentieth century industrial buildings, the mill’s two primary façades are characterized by repetitive bays of large, steel-framed windows set within utilitarian brick walls. Before air conditioning became widely available, factories relied on large window openings and expanses of glass to provide both natural ventilation and daylighting; now, these light-filled buildings, with their high ceilings and flexible floor plans, are regularly repurposed and converted to new uses.

Starting in late 2009, the Alden Mills building underwent a $15 million renovation; it was completed in early 2013. Forty-seven loft apartments occupy the building, with a portion devoted to commercial space at the corner of Marigny and Decatur Streets. As the project utilized both federal and state historic tax credits, it was required that key character-defining features of the structure be preserved. Because the building’s original rolled steel windows were still intact, in fair to good condition, and considered highly significant, it was decided early in the project to restore rather than replace them. This case study describes the process and challenges that the project team faced in restoring these historic windows while satisfying the current building codes and standards for thermal comfort and impact resistance required in hurricane-prone zones.


While steel windows gained popularity as replacements for wood windows in the 1890s, their manufacture did not become widespread or standardized until the following decade. In 1907, the Crittall Manufacturing Company of England granted the Detroit Steel Products Company the exclusive right to fabricate and sell their well-known Fenestra brand of steel windows in the United States. The patented Fenestra joint, in which one rolled bar of steel was passed through a slot in a second bar to create an interlocking connection, was marketed for its attractive unique appearance, its economic use of steel, and the strength of the sash. Other companies soon followed with their own patented designs, among them the United Steel Sash Company in 1910, the International Casement Company (later Hope’s Windows) in 1912, and Luptons.

These companies marketed their products to architects, engineers and building owners through trade publications, catalogues, and even the occasional popular magazine. A 1910 edition of the Saturday Evening Post featured a full-page advertisement for Detroit-Fenestra windows (see Figure 4). As the text noted, Fenestra windows were made in standard sizes and configurations–a “radical departure” that insured “immediate deliveries and quick construction.”[2] Other cited benefits included the windows’ low cost, permanence, ease of installation, and fire protection. It was even claimed that the 25% increase in light transmission afforded by the thin steel frames relative to heavy wooden sashes and mullions would boost employee efficiency and lower production costs.[3]

Because the Alden Mill was constructed in two distinct phases, the building’s windows reflect this shift in technology and production. The windows in the original 1905 “shoebox” portion of the building were made with mitered brazed muntin connections, a common method of fabrication at the time, while the 1916 “hatbox” addition used stock Fenestra windows. Besides visible differences in ventilator configurations, and divided lite patterns, the standard “hatbox” window was also 18” wider than its “shoebox” counterpart.

While the desire for fireproof buildings drove the early demand for steel windows, particularly in factories and warehouses, they soon gained widespread acceptance for their clean, modern, streamlined aesthetic.[4] Initially marketed just for industrial use, by the 1920s steel windows could be commonly found in institutional settings, public buildings, and even some private residences.


Despite suffering from varying degrees of corrosion, wear, and bent or broken frames, the majority of the Alden Mill’s original windows had fortunately not deteriorated past the point of repair. While some sashes had been modified over the years to accommodate doors, mechanical vents and other intrusions, most retained their original frames, glass and hardware. Nearly all were covered in layers of lead paint that would have to be removed during the restoration process.

As the architect of the project, studioWTA surveyed the 165 existing windows that could be catalogued into 14 distinct types based on size, ventilator locations, and the number of divided lights. The dominant window type found within each “shoebox” bay measured 4’-1 x 10’-9”, with a 4 x 6 divided lite configuration and two pivoting ventilators. The dominant “hatbox” window was slightly larger, measuring 5’-7” x 10’-9” with a 5 x 7 pattern of lites and only one ventilator. The largest windows in the building were located on the north wall of the “hatbox, where oversized units 17’-0” wide by 12’-6” high flooded the former mill interior with daylight.

Some of the windows had been covered by plywood or sheet metal prior to the start of construction; it’s believed these coverings protected the windows from further deterioration in recent years, but their condition wasn’t known until demolition was underway. The general contractor undertook a detailed window inventory and condition survey, noting in particular which units would be restored in-situ, and which would be restored off-site. Windows were only removed if the jamb, header or sill component(s) were heavily deteriorated. (These required the most restoration efforts but were also the easiest to removed due to deterioration of anchorage to the brick.) They were brought off-site to be stripped and brought back on-site for actual restoration. The windows that remained in place were subjected to a heavy industrial epoxy primer to penetrate and seal the existing rust, since stripping was not an option.

Of the existing windows, 78% of the “shoebox” windows were repaired in place, while 80% of the “hatbox” windows were repaired off-site. Approximately 12% of the steel windows in the converted building needed to be fabricated from scratch to match the existing units. After a lengthy search did not turn up any manufacturer who could produce an exact replica, it was decided that the new units–19 in all–would be made in-house using material salvaged onsite. The contractor’s inventory therefore also identified which windows would be removed and dismantled to provide the necessary bar stock, hardware, and other component parts. In addition to window removal due to component deterioration, some removal resulted from the design of on-street entries to the live/work ground floor units.


Because of the conversion of the building to residential and commercial use, the windows needed to be upgraded to meet modern building codes and standards. The original windows were mostly comprised of single panes of clear and wire glass–nominally 12” x 18” in the “hatbox” and slightly narrower and taller in the “shoebox”–held in place with glazing clips and putty. As-is, they simply could not provide the level of thermal comfort expected of today’s windows, nor could they meet the impact-resistance requirements of a hurricane-prone climate. Replacement with insulated double glazing was not an option, as the 1-3/8” muntin profile did not have the required depth to properly set the sandwiched panels. Instead, it was decided to replace all of the glazing with low-emissivity 7/16” laminated glass. This would meet the wind load requirements and also–when combined with weatherstripping at the operable sashes and adjustable MechoShades–provide adequate daylighting without excessive heat gain or loss.

The project’s structural engineer also evaluated the window frame types for their ability to withstand design wind loads. It was found that largest windows, on the north side of the “hatbox,” needed to have to additional 3”x½” steel stiffener bars attached to their intermediate mullions in order to meet code.

A particularly interesting challenge concerning the restoration of the “hatbox” windows was how to replicate the distinctive flared profile, found on both the muntins and frames, that was characteristic of the Fenestra brand. After exploring alternatives, it was determined that a sealant product could be used to economically and effectively recreate the contour where needed.

Detailed specifications were developed that identified the particular products–from paint finishes to sealants–considered to be compatible with the historic steel windows. Procedures were laid out for the sequencing of tasks which generally involved the following: removing the glass; removing the existing paint and corrosion; patching and repairing the frame (off-site where required); blasting and coating the frame with primer; installing new glazing, caulking; and applying the finish paint.

As is often the case with historic buildings, some unforeseen issues appeared during the course of construction. One of the most significant involved the deteriorated condition of several of the lintels above the window openings. Due to water infiltration, the existing steel channels had corroded within the masonry walls causing the adjacent bricks to spall. In particularly bad instances, structural reinforcing was required along with patching of the masonry surface. These repairs, too, were tested prior to their widespread application. Existing sill components were also in advanced states of deterioration, preventing proper sealing of the windows around the entire perimeter. The sill was constructed of the same components as the jamb, creating a continuous edge around the perimeter for weather-tight application of sealant.

Steel windows are anchored at the jamb with a fin that extends into a mortar joint within the masonry wall. Without proper maintenance, this jamb component deteriorates from rust and compromises the integrity of the structural connection. For existing windows in the advanced state of disrepair, the design and construction team developed a new jamb detail that would allow for salvaging and restoration of all intermediate window components. New jambs were composed of a 2-½” x ½” steel flat bar and 1” equal leg steel angle. This allowed for predrilled holes in the flat bar for installation of thread rod anchors into the newly filled brick mortar pockets.

The work, which involved the coordination of multiple subcontractors, had to comply with the National Park Service’s standards for steel window restoration.[5] Before the project could begin in earnest, however, the selected materials and process were first tested on a sample window to ensure compliance and to work out strategies.


As the 511 Marigny project illustrates, it is possible to restore and upgrade historic steel windows when they are an important character-defining element of a building. While the cost of restoration may sometimes exceed the comparable cost of replacement windows, the difference can often be overcome when historic tax credits are factored into the equation. Costs, too, must be weighed against the many benefits that come from choosing restoration over wholesale replacement. Besides the environmental upside of keeping discarded materials out of the landfill, restored windows contribute immensely to the authenticity of the building. This is especially important in former industrial structures where windows often make up well over 50% of the façade. In the case of 511 Marigny, their preservation is particularly significant as they tell the story of craftsmanship, innovation and change in the development of the modern steel window.


Developer/Client: Julian Mutter; Architect: studioWTA; Structural Engineer: Avegno, Bailey & Assoc., Inc.; General Contractor: Gibbs Construction, LLC

Case Study prepared by Beth Jacobs of Clio Associates, with input from studioWTA. 

[1] Annual Report of the Bureau of Statistics of Labor for the State of Louisiana (Louisiana: Bureau of Statistics of Labor, 1918): 147.

[2] Advertisement for Detroit-Fenestra windows, Saturday Evening Post, 1910. [Need complete citation].

[3] Ibid.

[4] This was an era when concern over fireproof construction was paramount. Underwriter’s Laboratories was established in 1894 to test fireproof building assemblies. By 1902 a new school of insurance engineering was established at MIT. See “Fire Protection Taught as Science,” Times Picayune, June 29, 1902.

[5] Sharon C. Park, “The Repair and Thermal Upgrading of Historic Steel Windows,” Preservation Brief No. 13 issued by the National Park Service, Department of the Interior.