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Early 20th-Century Building Materials: Introduction

Historic Preservation

A building typically must be 50 years old or older to be considered a "historic property," one eligible for listing in the National Register of Historic Places. Facilities constructed as late as the 1950s and 1960s are being examined now for their historic significance and possible preservation. This has led to the investigation of "modern" construction materials and methods and discussions about appropriate preservation techniques.

In 1995, the National Park Service cosponsored the first national conference devoted to preserving architecture of the recent past. This conference was followed by another conference in 2000, development of a Recent Past Initiative Web site, and creation of the nonprofit Recent Past Preservation Network. Since then, an increasing amount of historic and scientific research on 20th-century building materials has been published.

Many of us may shudder at the thought of aluminum siding as historic and worth preserving. However, historic significance is not a matter of preference or taste. Significance is defined by the trends, events, and products that contributed to our history. For instance, Victorian-era homes were considered hopelessly out of date and unfashionably gaudy during the early and mid- 20th century. Thousands of them were demolished. The remaining Victorian homes are now valued for their intricate architecture, history, and beauty.

As people become more fascinated with buildings of the 20th century, increasing attention will be given to their preservation. The emerging popularity of mid-20th century modern design and the "international style" has stirred interest in preserving and renovating structures from the 1930s through the 1960s.

Over time, this interest is likely to produce more research, information, and appropriate replacement materials that will make it easier for the Forest Service to care for its stock of 20th-century structures so they can continue to support the agency's mission well into the 21st century.

Standards of Treatment

Any work on Forest Service facilities that are historically significant should be carried out following The Secretary of the Interior's Standards for the Treatment of Historic Properties, available at There are four types of treatment: preservation, rehabilitation, restoration, and reconstruction. Most Forest Service facilities work, other than basic maintenance, can be classified as rehabilitation. Rehabilitation of historic properties may include alterations to meet continuing or changing uses. Alterations must follow the Rehabilitation Standards to ensure that the property's historic character is retained.

The Secretary of the Interior's Standards and Guidelines for the Treatment of Historic Properties allows for the use of substitute materials under certain conditions. If using the original type of material is not technically or economically feasible, a compatible substitute material may be considered. Substitute materials should convey the visual appearance of the material that is being replaced. In addition, they must be physically or chemically compatible. Consult with your heritage staff and State Historic Preservation Office to identify appropriate treatment methods and to determine whether the substitute materials you are considering are acceptable.

Rehabilitation Standards

Rehabilitation is defined as the act or process of making possible a compatible use for a property through repair, alterations, and additions while preserving those portions or features which convey its historical, cultural, or architectural values.

  1. A property will be used as it was historically or be given a new use that requires minimal change to its distinctive materials, features, spaces, and spatial relationships.

  2. The historic character of a property will be retained and preserved. The removal of distinctive materials or alteration of features, spaces, and spatial relationships that characterize a property will be avoided.

  3. Each property will be recognized as a physical record of its time, place, and use. Changes that create a false sense of historical development, such as adding conjectural features or elements from other historic properties, will not be undertaken.

  4. Changes to a property that have acquired historic significance in their own right will be retained and preserved.

  5. Distinctive materials, features, finishes, and construction techniques or examples of craftsmanship that characterize a property will be preserved.

  6. Deteriorated historic features will be repaired rather than replaced. Where the severity of deterioration requires replacement of a distinctive feature, the new feature will match the old in design, color, texture, and, where possible, materials. Replacement of missing features will be substantiated by documentary and physical evidence.

  7. Chemical or physical treatments, if appropriate, will be undertaken using the gentlest means possible. Treatments that damage historic materials will not be used.

  8. Archeological resources will be protected and preserved in place. If such resources must be disturbed, mitigation measures will be undertaken.

  9. New additions, exterior alterations, or related new construction will not destroy historic materials, features, and spatial relationships that characterize the property. The new work will be differentiated from the old and will be compatible with the historic materials, features, size, scale and proportion, and massing to protect the integrity of the property and its environment.

  10. New additions and adjacent or related new construction will be undertaken in such a manner that, if removed in the future, the essential form and integrity of the historic property and its environment would be unimpaired.

More Information

The following Web and print resources contain more information about early 20th-century building materials and the treatment of historic structures.

Web Sites

The MTDC Facilities Toolbox section on historic facilities,, contains general information on dealing with historic facilities. This material also is available on the Internet at

Clem Labine's Traditional Building,, includes a database of products and suppliers.

Ian Evans' World of Old Houses,, contains a guide to maintenance and restoration.

National Trust for Historic Preservation's Modernism and the Recent Past Web page,, provides information on modern architecture and materials.

The Recent Past Preservation Network,, is a nonprofit organization dedicated to the study of modern architecture and materials.

The Secretary of the Interior's Standards for the Treatment of Historic Properties with Guidelines for Preserving, Rehabilitating, Restoring, and Reconstructing Historic Buildings contains requirements for appropriate treatment of buildings and sites, including health and safety concerns, accessibility, materials, energy efficiency, and additions. It is available in print form or on the Web at

Books, Journals, and Reports

The APT Bulletin,, is the journal of the Association for Preservation Technology, focused on the science of preservation.

Heritage Preservation and National Park Service, 1998. Caring for Your Historic House. New York: Harry N. Abrams, Inc. National Park Service guidance on maintenance and repairs of historic features.

The Journal of Architectural Conservation,, contains international academic and scientific research.

The Old-House Journal,, is a layperson's periodical guide to architectural styles, materials, and preservation.

Guedes, Pedro, ed. 1979. Encyclopedia of Architectural Technology. New York: McGraw-Hill Book Co. Explains the history and development of construction systems and materials.

Jandl, H. Ward. 1991. Yesterday's Houses of Tomorrow: Innovative American Homes 1850 to 1950. Washington, DC: The Preservation Press. Experimental construction and early materials.

Jester, Thomas C., ed. 1995. Twentieth-Century Building Materials: History and Conservation. New York: The McGraw-Hill Companies. Excellent source for specific building materials and product names.


The authors gratefully acknowledge the contributions of those who provided photographs for this publication:

Keith Lannom, Tellico district ranger, Cherokee National Forest, Southern Region

Kelly Keim, archeological technician, Lewis and Clark National Forest, Northern Region

Sandi French, forest archeologist, Lewis and Clark National Forest, Northern Region

About the Authors

Richa Wilson is the regional architectural historian for the Intermountain Region and vice chairman of the board of directors for the nonprofit Traditional Buildings Skills Institute. She has a bachelor's degree in architecture and a master's degree in historic preservation. As a Peace Corps volunteer, Wilson served as head of the building inspection section in Blantyre, Malawi, and provided architectural services to Habitat for Humanity and Save the Children. Wilson worked in private practice in Washington, DC, and Oregon before joining the Forest Service in 1998.

Kathleen Snodgrass came to MTDC as a project leader in 2001 from the Nez Perce National Forest, where she had been the facilities architect for about 7 years. Before becoming facilities architect, she had worked in facilities, landscape architecture, land line, and general engineering for the Nez Perce National Forest. Snodgrass also spent about 10 years working in highway design and construction with the Idaho Division of Highways after graduating from Washington State University in 1974 with a bachelor's degree in architectural studies.

Single copies of this document may be ordered from:

USDA Forest Service, MTDC
5785 Hwy. 10 West
Missoula, MT 59808–9361
Phone: 406–329–3978
Fax: 406–329–3719

Electronic copies of MTDC's documents are available on the Internet at:

For additional technical information, contact MTDC.

Phone: 406–329–3900
Fax: 406–329–3719

Forest Service and Bureau of Land Management employees can search a more complete collection of MTDC’s documents, CDs, DVDs, and videos on their internal computer networks at: