Ruins Stabilization in the Southwestern United States
Publications in Archeology 10
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Chapter 1

This book is a guide to the methods, materials and techniques employed in the stabilization and maintenance of prehistoric and historic structures in a ruinous condition. It is designed especially for construction and maintenance personnel of local, State and Federal agencies charged with the care of land on which there are historic structures worthy of preservation in an "as is" condition. The publication is an outgrowth of a very early ruins stabilization manual written by the late R. Gordon Vivian in 1949 for the National Park Service, and revised in 1962.

The interests served by the two earlier manuals were confined largely to a few specialists of the National Park Service whose duties involved the preservation and maintenance of prehistoric and historic structures. Today, however, a greatly expanded program of preserving cultural properties on a nationwide scale has prompted the need for disseminating guidelines on a much broader base. It should be made abundantly clear that Mr. Vivian's original work is so basic and fundamental that much of it remains intact. Most sections were revised or amplified, and new ones were added as required.

The present edition incorporates important new material reflecting not only the development of ruins stabilization practices, but the urgent need for getting this information from Federal into State and regional channels where it may serve a useful purpose for all who attempt to preserve historic structures. While emphasis is given to definitions, principles, and standards, considerable effort is made to describe the process of stabilizing a given structure, and to evaluate the effectiveness and durability of the measures employed. This manual is concerned primarily with ruins stabilization in the southwest United States, although many problems and techniques discussed herein are applicable in other climates and regions.

The users of this book are encouraged to read another National Park Service publication, entitled Recording Historic Buildings (Washington, D. C., 1970) compiled by Harley J. McKee. As McKee stated so aptly in his work, "Only a productive partnership between Federal, State, and local governments, and private individual initiative can assure the adequate recording and successful preservation of our great national patrimony of historic architecture."

Keet Seel Ruin, Navajo National Monument, Arizona. Occupied intermittently through Pueblo I and Pueblo II periods (A.D. 1250-1286), the ruin was first excavated and stabilized in 1934 by a Civil Works Administration crew under the sponsorship of the Museum of Northern Arizona. Additional work by the National Park Service in 1958 and 1970 corrected numerous weaknesses, and recorded areas of the 1934 research not previously documented. Several types of wall construction are evident, including wattle and daub, masonry, vertical post-reinforced and horizontal post-reinforced.


The ruins stabilization program of the National Park Service is concerned with the preservation of historic and prehistoric architectural remains. The legal bases are derived from five general laws passed by the Congress of the United States: the Antiquities Act of 1906, the Act of 1916 establishing the National Park Service, the Historic Sites Act of 1935, the National Historic Preservation Act of 1966, and the National Environmental Policy Act of 1969.

General policies under which the program functions were formulated by the Advisory Board on National Parks, Historic Sites, Buildings and Monuments in 1938, by the Director's Committee on Ruins Stabilization in 1940, and by the Handbook for Ruins Stabilization, Part 2, Field Methods, 1962, codified and brought up to date in a Compilation of the Administrative Policies for the Historical Areas of the National Park System, revised, 1968.

The purposes with which the ruins stabilization program of the National Park Service is now concerned, and which will continue in the future, are five-fold: 1) the actual work of field crews preserving sites scattered throughout the Service, involving a wide range of structures; 2) the compilation of a complete inventory of archeological and historic structures, and the development, from this, of long-range priorities to cover the maintenance of stabilized sites and the stabilization of others, particularly those in National Park Service areas of increasing visitation and need for research and interpretation; 3) improvement of technology and the use of Space Age plastics and synthetics with emphasis on the preservation of adobe structures; 4) coordination with other units of the Service concerned with the combined excavation-stabilization of interpretive sites, and, wherever possible, further the development of techniques for preserving objects in situ and furnishings in museums; and 5) cooperation with other Federal, State, and local agencies by providing them with information and expertise on professional methods of preservation.

The beginnings of Federal involvement in ruins stabilization can be traced back to 1889 when a $2,000 memorial to Congress provided for the stabilization and repair of Casa Grande Ruins near Coolidge, Ariz. Three years later, in June 1892, President Benjamin Harrison signed an executive order recommended by the Secretary of the Interior reserving Casa Grande Ruins and 480 surrounding acres for permanent protection because of its archeological value. Thus the first national archeological reservation in U. S. history was established, preceded by the first ruins stabilization attempts (Lee, 1970, p. 20). Other pioneering stabilization and repair jobs were performed at Chaco Canyon, Canyon de Chelly, Mesa Verde, Tuzigoot and Wupatki, all of which will be mentioned later in this volume.

Recognizing the need to devise means of preserving sites which were rapidly deteriorating under his charge, Frank Pinkley, Superintendent of the former Southwestern National Monuments, Coolidge, Ariz., organized a Mobile Ruins Stabilization Unit in 1937 with a field station at Chaco Canyon National Monument. It was originally set up as a program of the Civilian Conservation Corps by inter-bureau agreement of the National Park Service and the Bureau of Indian Affairs. The National Park Service furnished materials, equipment, and supervision, and the Navajo Agency supplied their camp and a crew of 25 Indian CCC enrollees. An archeologist-foreman and an engineer-foreman supervised. The goal of the Indian mobile unit was to move from area to area among the 14 southwestern archeological and historic monuments, accomplishing emergency, comprehensive, and maintenance stabilization.

As a result of economic retrenchment on a national scale, the Navajo Agency was forced to reduce enrollee strength from 25 to 20 in 1938, and to lOon July 1, 1940. The unit was disbanded in April of 1942 for the duration of World War II, and was reactivated in October of 1946. Since the latter date, funds for its operation have been provided through the Maintenance and Rehabilitation Account of the National Park Service. Labor continues to be recruited on a WAE (when actually employed) basis, largely from the Navajos, all of whom are qualified by previous training and experience in stabilization. In fact, one or two of the older crew members are former CCC enrollees, while the younger members are "second generation," their fathers having been employed in the Mobile Unit before them. Native patience, artisanship, and resourcefulness, coupled with adaptation to isolated locations under camp conditions, have earned for the Navajo first choice as members of specialized field crews. Their employment is consonant with our National policy of assisting minority groups, and of providing gainful and useful work for people living in economically depressed areas.

Significantly, employment has not been confined to the Navajo. In recent years, other minority groups, including the Apaches and Spanish-Americans, have been attracted to the program. The San Carlos Apache have been employed on an archeological project at Gila Cliff Dwellings in New Mexico, and on the stabilization of Besh-Ba-Gowah, a city-owned ruin dating in the 14th century A. D., near Globe, Ariz. A deep and abiding dedication to the preservation of mission architecture, combined with a unique skill in working with adobe by the all-Spanish-American crew was largely responsible for the excellent work at the important site of Pecos National Monument in New Mexico.

Work during the formative years of the Mobile Unit's history was concentrated at two or three of the huge surface ruins of Chaco Canyon and at the large West Ruin, Aztec. Stabilization in those early years was accomplished without blueprints or manuals, the work consisting of a unique combination of art, archeology, and a building science in its infancy. Numerous thorny problems involving control of erosion by capillary moisture, repair of wall breaks, support, and realignment, were new and without precedent. Standardized and proven remedial measures were unknown. Wherever possible, standard building procedures were employed, but in many instances untried techniques had to be devised and the results observed and analyzed with the passage of time. Because of obvious structural differences between prehistoric and modern buildings, stabilization has sometimes resulted in a compromise between sound building practice and an attempt at authenticity of appearance.

Clear and complete records were maintained for each project from the beginning of the Mobile Unit's work in 1937. Standardized record sheets were designed and used for each room or unit, together with photographic pages showing both the general conditions and important details of the site. The major objectives were to set down in permanent form the condition of the structure prior to stabilization, and to record stabilization measures taken, including new construction. Thus, a stabilization record evolved into a structural history of a site or an architectural unit of that site. Field notes were maintained as a daily log. Photographs, recorded observations, experiments, special reports and job unit reports were amassed over the years, all of which proved valuable for present and future work. Eventually the repair jobs which were similar in many sites became standardized, involving the same proven technique or group of techniques. More than three decades of periodic inspections of earlier work permitted reliable evaluations as to success or failure and, usually, the reasons therefore. Moreover, based on previous performance standards, it was possible to estimate rather closely the costs of various proposed projects in terms of measured wall areas and quantities, and the material and labor required for stabilization. This data and experience resulted in the formulation and evaluation of stabilization techniques and materials which provide a sound basis for the discipline of preserving prehistoric architectural remains.

The ruins stabilization program of the National Park Service is now carried on at its Archeological Center in Tucson in cooperation with the University of Arizona. The program represents an activity within the Division of Cultural Properties Conservation of the Center, and is an integral part of the Center's operation. A permanent staff of four full time employees are engaged in stabilization work throughout the year. During the summer months, from 40 to 60 temporary employees, including graduate students in anthropology, are organized into crews and are sent to the field.

National Park Service archeology is unique in a number of ways. It approaches the task from a comprehensive viewpoint and embraces research, preservation, and interpretation—a program tailored to the mission of the Service. National Park Service project archeology, institutional archeology, and ruins stabilization all benefit from a cooperative approach. Experience has shown that where the Service project archeologist and an institutional archeologist from a university work hand-in-hand to further the goals of the ruins stabilization program, excellent and durable results are usually obtained. There is absolutely no reason for conflict among government, university, or privately endowed institutions in the allied fields of archeology and stabilization, provided standards and aims are clearly established and implemented on a cooperative basis. Moreover, as funds become available, National Park Service archeologists and historians increase their cooperation with other Federal and State agencies, as well as with local organizations and civic groups. Stabilization requires the expertise of archeologists, architects, engineers, manufacturers, material suppliers, and labor. Each group provides distinct talents which should be sought for every project.


For purposes of discussion in this guidebook, a historic structure is considered to be a work of man, either prehistoric or historic, consciously created to serve some form of human activity. A historic structure, by nature or design, is usually immovable. Besides buildings of various kinds, the term includes works such as dams, canals, bridges, stockades, forts and associated earth-works serving a similar purpose, Indian mounds, gardens, roads, mill races and ponds. By definition, ruins are classified as historic structures and will be accorded treatment as described under the term stabilization. It is emphasized that in this volume we are dealing with structures or, more usually, with mere remnants of structures in various stages of deterioration.

In professional circles, the words preservation, restoration, reconstruction and stabilization frequently stir up a war of semantics. It is small wonder that the layman has difficulty in distinguishing the meanings of these terms. Both within and outside the National Park Service, there is a growing consensus that these words logically come under the broader, all-inclusive phrase "conservation of our nation's non-renewable historic resources." Our definitions of preservation, restoration, reconstruction and stabilization are:


Preservation, used architecturally, refers to the stabilization of a structure in its existing form by preventing further change or deterioration. Preservation, since it takes the structure as found, does not relate to a specific period in time and is the most authentic treatment of a historic structure (Bullock, 1966, p. 1, and Compilation of the Administrative Policies for Historical Areas of the National Park System (1968, p. 21).


Restoration means the process of accurately recovering, by removal of later work and the replacement of missing original work, the form and details of a structure or part of a structure, together with its setting, as it appeared at some period in time. The value of a restoration is measured by its authenticity.


Reconstruction refers to the re-creation of a building by new construction. Although re-creating the form and details of a vanished structure should be based on all the historical, archeological, and architectural data available, very often the evidence is far from complete, thus detracting from both the accuracy and intellectual integrity of the reconstruction.


Stabilization involves those construction methods, materials, and techniques used to minimize the deterioration of a structure, thereby accomplishing the objective of preservation. Hence, the preservation procedures and techniques designed to arrest further deterioration of ruins are encompassed by the phrase ruins stabilization.

Ruins Stabilization

Ruins on unexcavated sites should be stabilized only to that extent which is necessary to preserve them for further investigation. Sites other than those excavated in advance of unavoidable modern construction should not be excavated until adequate provisions have been made to stabilize ruins as they are exposed. In cases where ruins are too fragile for direct visitor contact, or where deterioration would result from sustained contact, public use should be strictly limited or prohibited. The deliberate creation of ruins out of whole structures by the owner, whether at local, State or Federal levels, is contrary to currently accepted environmental and esthetic principles. Such practices are theatrical, unauthentic, and fraudulent, serving only to deceive the public.

Comprehensive ruins stabilization involves careful planning to place a prehistoric or historic structure in a sound structural condition, and to preserve its appearance immediately following excavation and study. Usually this is the final action taken in prehistoric sites intended for interpretation and visitor-use.

Comprehensive ruins stabilization usually follows closely upon the heels of excavation, and requires the use of evidence from the excavation and other documents. Most comprehensive stabilization requires some archeological excavation, either as a part of the stabilization project, or as a separate but closely related project of interpretive research.

Appearance is a major consideration of comprehensive ruins stabilization. Every effort is made to satisfy the requirements of stability and appearance. It is permissible to patch holes which will approximate the original materials. It is permissible to realign walls, returning them to their original positions, to use force to push them back into plumb position, or to change them from their existing alignment. Parts or elements of structures may be replaced or reset in their original position. This might include resetting part of a fallen wall or resetting a dislodged beam. Original material or newer materials may be substituted for missing parts of a structure. A variety of techniques may be employed in the reinforcement of walls or foundation; internal structural reinforcement members may be built into a wall and concealed, or external ties may be used if these provide the best solution.

Comprehensive ruins stabilization differs from restoration-reconstruction, in that no attempt is made in the former process to restore the structure to its complete, in-use appearance. The surviving original, plus the fallen or displaced elements revealed in the archeo-historical record, limit the extent to which the structure may be returned to its original appearance. The replaced or repaired elements must be readily distinguishable upon close scrutiny, but their appearance should match that of the original and not be apparent to the casual observer.

An excellent definition of stabilization is incorporated in the International Charter for the Conservation and Restoration of Monuments and Sites. It appears in the "Decisions and Resolutions of the International Congress of the Architects and Technicians of Historic Monuments," Venice Charter (1964). It is quoted in its entirety, with italics supplied, indicating the passage which appropriately describes "ruins stabilization" as applied in the United States.


Article 15. Excavations should be carried out in accordance with scientific standards and the recommendation defining international principles to be applied in the case of archeological excavation adopted by UNESCO in 1956.

Ruins must be maintained and measures necessary for the permanent conservation and protection of architectural features and objects must be taken to facilitate the understanding of the monument and to reveal it without ever distorting its meaning.

All reconstruction work should however be ruled out a priori. Only anastylosis, that is to say, the reassembling of existing but dismembered parts can be permitted. The material used for integration should always be recognizable and its use should be the least that will ensure the conservation of a monument and the reinstatement of its form.

Two additional terms deserve mention. Related stabilization includes those measures taken in proximity to the structure for its prolonged preservation. The work must contribute to the stability of the structure and not detract unduly from its appearance. Typical examples of related stabilization projects include the walkway within the council chamber at Ocmulgee, the river diversion devices in the vicinity of White House and Antelope House at Canyon de Chelly, and of Pueblo del Arroyo in Chaco Canyon, the retaining wall in front of the Lower Ruin at Tonto, the deep interceptor drainage line and surface dike at Aztec Ruins, and the protective roof of Casa Grande.

After a structure has been stabilized and prepared for public view, it is considered to be in maintenance status. Sufficient annual funding should be programmed for maintenance stabilization whereby systematic inspections can be made to check and repair minor erosion from natural and human forces before the structural integrity of the building is threatened. In addition to the routine of cleaning up wind-blown or visitor-thrown debris, weed control, renewal of walking surfaces, and the cleaning of drains, maintenance stabilization includes the renewing of wall plaster, repointing wall joints, and resetting loose or missing masonry elements. Maintenance defined simply is the routine, recurring work that is necessary to keep prehistoric and historic structures in such a condition that they may be used for their intended purpose and designed capacity. It includes the replacement, overhaul, or reprocessing of worn and deteriorated materials. Attempts should be made to keep the structure in the same condition as it was when acquired, or when the responsibility for its maintenance was assumed following stabilization. Ideally, maintenance personnel who are responsible for the structure also will have participated in the stabilization. If this is not possible, the maintenance personnel should be given special training and orientation.

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Last Updated: 16-Apr-2007