Carefully Select Roofing Materials to Maintain the Character of Historic Buildings

Selecting a historically appropriate roofing material is often restrictive as a simple matter of economy. Not everyone can afford a new slate roof. But individually landmarked structures and those in local historic districts are often monitored by historic district commissions (HDCs) that typically require property owners to replace in-kind or with an otherwise historically appropriate material.

Although the preference is replacement in-kind, an intelligent argument for an alternative can often be made. The HDC can consider other materials that were available at the time of construction, as well as what buildings of similar style in the community have on their roofs. A Queen Anne may have started with a polychromatic Vermont slate roof, but the commission can consider that nearby Queen Annes have monochromatic Monson slate or even cedar shingles. A Greek Revival may have a silver-coated tin roof, but few would argue with a homeowner willing to replace it with standing-seam copper. Let’s look at several American building styles and the materials used to roof them.

Colonial Styles, 1620 to 1780

From the New England Salt Box to the Dutch-vernacular homes of upstate New York, the earliest structures in the American colonies were roofed with wood shingles.

From the New England Salt Box to the Dutch-vernacular homes of upstate New York, the earliest structures in the American colonies were roofed with wood shingles.


From the New England Salt Box to the Dutch-vernacular homes of upstate New York, the earliest structures in the American colonies were roofed with wood shingles. It is a myth they were covered with hand-split shakes because these sometimes do not hold up well. Wood shingles were easily made by planing down the shakes to a uniform thickness for ease of installation.

In the Northeast, Eastern white cedar was the typical material used while cypress was often used in the South. Western red cedar was not used much in the eastern U.S. until after the 1850s and should not be considered appropriate on a circa-1820, Federal-style structure in Connecticut. Eastern white cedar, however, rarely lasts longer than 10 years in a roofing application. Instead, preservation architects now specify Alaskan yellow cedar. Predominantly distributed from British Columbia, this dense wood is favored because of its longevity and because it develops a silvery patina, like Eastern white cedar, within one year.

Federal and Neoclassical Styles, 1780 to 1820

Many of these buildings have low-slope roofs and are often obstructed by a balustrade that runs across the top of the eaves. In congested, urban environments, the roof may not even be visible from the street. This raises the obvious question: What needs to be done when an element of the exterior is not within the street view? Most HDCs use that standard question to limit their purview over a proposed alteration. If your roof falls into this category, then you should pick the most enduring and sustainable material you can afford.

These structures were not often originally covered in slate, though many are today. Original roofs were wooden shingles—less than ideal on a roof with a shallow pitch. In limited instances, standing-seam or flat-lock-seamed roofs are seen on these building styles. To find out what’s appropriate, check out roofs on structures of the same style in your neighborhood and neighboring communities.

The mansard roof is the character-defining feature of the Second Empire style. A mansard is essentially a hipped gambrel. The lower roof, between the eaves and upper cornice, is most often covered in slate.

The mansard roof is the character-defining feature of the Second Empire style. A mansard is essentially a hipped gambrel. The lower roof, between the eaves and upper cornice, is most often covered in slate.

Greek Revival, 1820-50

This style also features a low-slope roof, typically 4:12. Although the original roof material may have been wooden shingles, many of these roofs in the Northeast were replaced by a more sustainable material long ago. Flat-lock tin or terne-coated steel were typical from the late 1800s on. Because many of these structures also have box gutters at the eaves, keep in mind that relining these systems is costly and will need to tie in to the new roof material. (See “Traditional Gutter Systems in North America”, March/April issue, page 56, or bit.ly/1Mw7Qek.) It is not uncommon for an affordable membrane, like EPDM or TPO, to be used on the majority of the roof while a costlier appropriate material, like copper, covers the visible, projecting “porch” roof.

PHOTOS: Ward Hamilton

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Project Profiles: Historic Renovation

Maine State House Dome Restoration, Augusta, Maine

Team

COPPERSMITH: The Heritage Co., Waterboro, Maine
GENERAL CONTRACTOR: Consigli Construction Co. Inc., Portland, Maine
ARCHITECT: LEO A DALY, Minneapolis
ENGINEER: Becker Structural Engineers, Portland

To remain proportional with the larger building, a new, higher copper-covered dome was built to replace the original cupola.

To remain proportional with the larger building, a new, higher copper-covered dome was built to replace the original cupola.

Roof Materials

Working 200 feet in the air on elaborate staging, carpenters, coppersmiths, engineers and other construction workers replaced more than 7,000 square feet of copper on the dome. The existing unique, curved copper components were carefully removed and saved to serve as models for the new components.

A full sheet-metal shop, consisting of an 8-foot brake, 52-inch jump shear and benches, was set up onsite at the 63-foot elevation mark, along with five cases of 20-ounce copper (about 12,880 pounds). Each copper component was carefully measured, cut and bent onsite, and then installed.

The compound curving components were made in The Heritage Co.’s “home” shop, using a shrinker/stretcher machine and an English wheel. Then, the copper was handformed over custom-made wood forms. Care was taken to exactly match the size and configuration of the existing components, as well as the seam layouts that were prevalent in the original copper work

Approximately 15 to 18 percent of the copper was waste because of the curved nature of many of the components. The waste was made into copper clip stock for the roof installation or recycled.

COPPER MANUFACTURER: Revere Copper Products Inc.
COPPER SUPPLIER: Beacon Sales Co.

Roof Report

The Maine State House was originally designed by renowned architect Charles Bulfinch in 1832. The dome was added in 1910 as part of a major remodeling and expansion project that ultimately created the building’s current appearance based on designs by G. Henri Desmond.

The original façade was preserved during remodeling, though the length of the building was doubled to 300 feet by extending the north and south wings. To remain proportional with the larger building, a new, higher copper-covered dome was built to replace the original cupola. The new dome rises to a height of 185 feet and is topped by a gold-clad copper statue, called “Lady Wisdom”, designed by W. Clark Noble.

Over time, weather damage and holes caused by hail strikes on the top of the dome caused leaks in the building. The seams between the copper sheets also caused problems for the underlying steel and concrete structure of the dome. The work included the installation of expansion joints, repairs to prevent water infiltration and restoration of the cupola (located between the top of the dome and Lady Wisdom), using a highly durable paint system. Lighting upgrades, copper repairs and the restoration of the gilded Lady Wisdom statue located atop the dome were also part of the project.

The dome’s structural system and framing were analyzed by Becker Structural Engineering one year in advance of dome construction, so Consigli Construction could create a 3-D model for staging to eliminate interior shoring.

Overall, this project restored one of Maine’s most significant historic landmark buildings, returning its signature copper dome and gilded Lady Wisdom sculpture to their original intended conditions.

PHOTO: Consigli Construction Co. Inc.

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