The Conservation Process
by John Greenwalt Lee assisted by Morgan Gilpatrick
Written in 1997 for The Architectural Conservation of the Wyck House: The Building as a Museum Object
Most preservation projects are managed using a format developed for new construction, taking for granted that it can be successfully adapted to preservation. During my twenty-four years as a building materials conservator, I have observed that what is practical for a new building often works against the goals of preservation. The process is not compatible with the principal goal of preservation: to save as much original material as possible. Many of our older buildings have suffered the consequences:
Many underlying problems have gone undiscovered and uncorrected.
Historic fabric has been removed or lost.
Materials have been introduced which have unknown long-term effects.
The combination of alterations, uncorrected problems, and new materials have caused further and more extensive deterioration, and, as a result, still more of the artifact has been lost.
The Design-Driven Process versus an Investigation and Treatment Process
New construction uses what I will call the Design-Driven Process. Its goal is the creation of a new object. The process has been developed to turn an idea into a three-dimensional reality. The underlying forces that drive it are easier to visualize when the sequence is reduced to its simplest form. Think about what it takes to design a house. The sequence is initiated by the owner's need for a house. The architect designs the house and produces drawings describing it. The contractor translates those designs into materials, labor and cost. And finally, the carpenters, masons, and craftspeople act on the materials, in the presence of the design, to make the structure. The energy, ideas and information are all focused toward the final goal of the finished house. When arrows are used to represent the movement of these forces, they all move in one direction.
--> --> --> --> --> --> --> --> --> --> --> --> --> --> --> --> --> --> --> --> -->
Need -> Concept -> Design -> Plans -> Work -> Materials -> New Building
The conservation of our historic buildings requires a different approach, a process that begins with investigation and is adaptable to the changes that are an inevitable part of the process. For the purpose of this chapter I will call this the Discovery and Treatment Process. This sequence usually begins when materials fail or parts of the structure show signs of stress. When arrows are used to describe this process, they move in reciprocal directions effectively creating an evolving feedback loop:
--> --> --> <-- <-- <-- --> --> --> <-- <-- <-- --> --> --> <-- <-- <-- --> --> -->
Materials Failing <-> Investigation <-> Discovery <-> Testing <-> Treatment
The first arrows originate with the building and represent evidence of problems. Over the duration of the project, investigations, analysis, and work are focused at the building to discover the source of its problems and, later, to develop treatments to correct those problems. There is a continuous exchange between the information found in the building and the work of the investigative team.
Why is so much information necessary? Why do we need to investigate at all? Buildings are complex systems. The problems that initiate a project may only be symptoms of broader conditions that are hidden and unsuspected. Well-planned investigation and analysis can identify and prove the real root causes. Investigation early in the project can provide a foundation for planning the rest of the project. It is usually the only way to develop an understanding of the condition of the building elements, the underlying causes of these conditions, the nature of the materials used to construct and repair the building, and how everything fits into an overall sequence of construction and repair throughout the life of the building. The significance of all these clues needs to be interpreted, and placing them within the context of the evolution of the building requires expertise and should not be left in inexperienced hands. Well-planned investigation early in the project is necessary whether the goal of a conservation project is to uncover a previous building within an existing structure and restore it or simply to preserve some existing portions of the building and integrate them into a new structure.
Unknown conditions make responsible conservation incompatible with the Design-Driven Process. The Design-Driven Process was not meant to accommodate either the discovery process or the changes the project must undergo when investigation produces unexpected results.
Conflicts arise beginning with the planning of the project. For any project to be managed effectively, the plan, the budget, and the schedule must be worked out in advance. In new construction it is possible to know everything there is to know about the building. All of the project can be designed before work begins, and the number of possible variants can be reduced down to a manageable minimum. To get the new building built on schedule, it is necessary to figure out how it all fits together ahead of time - ruling out uncertainty.
Uncertainty is a natural part of the conservation process. Problems and important clues continue to turn up as elements of the building are disassembled and examined during treatment. New revelations have been known to alter the course of a project. This has created a crisis for many conservation project managers: Planning the project seems to be at odds with not having a definite picture of the whole project at the beginning. Owners, committees, and even architects find it easier to work on older buildings as if they were new buildings. What happens all too often with the Design-Driven Process is that the goal of preserving the artifact is either truncated or sacrificed.
Looking at the forces at work in the Design-Driven Process, it is immediately apparent why this conflict is inevitable. The arrows march in a single direction: What they reveal is that this process forces treatment to be prescribed before the causes of the problems are understood. It has been, and continues to be, the chief danger these buildings face today. The historic structure gets cut to fit the wrong solution. It succumbs to well-intentioned, misguided, and, most often, vigorous repairs.
A conservation project using the Design-Driven Process might look like this:
The owner of a house retains an architect to restore it. The owner and the architect agree that part of the scope of work includes repairing damaged parts of the building, and they agree that they want to save as much of the original material as possible. The architect recognizes that there are badly deteriorated areas of stucco on the exterior, but does not map or test the stucco; the examination is brief, consisting of tapping here and there, and scraping and prying off loose areas. Rather than investigation of the crumbling stucco as a symptom of larger processes of deterioration at work in the building, the original stucco is assumed to be failing on its own. The architect decides that much of the original material is weak and, in many areas, must be removed. After speaking to various product salespeople and a contractor or two, the architect then writes specifications for the work that will go out to bid.
In these specifications the architect states several things: that the contractor will test the stucco and be responsible for determining the soundness of any original stucco that is allowed to remain; that the contractor will also be responsible for coming up with an appropriate new stucco; that appropriate materials and techniques will be used to remove any coatings on the remaining stucco; and that the contractor will employ an expert to determine these things. The contractor is neither familiar with nor comfortable with hiring a consultant and assumes that a consultant will be expensive. He also knows that a consultant will require him to do things he doesn't want to do, which will alter his schedule. The contractor is not likely hire a consultant. If pushed, the contractor may consult with a product representative. The contractor plans for complete removal of the stucco, not knowing what the original stuff is and not wanting to be held responsible if it fails.
In the scenario above the architect sets the tone for the project by not analyzing either the condition of the stucco or the underlying causes of the deterioration. The decision about how the historic fabric was to be treated was shifted to the person least able to make that decision - the contractor. The contractor had neither the skills nor the experience to make that decision, and, having been brought into the process late, did not have enough information on which to base his decision.
The contractor was placed in the position of deciding the fate of the stucco and also the burden of cost. This is often the case. It is a chain of decision-making that works for a design process. If the cost seems too high, the architect has the option of asking other contractors to bid until one with a low enough bid is found. The architect can also go back to the drawing board, substituting cheaper materials, changing the design, or reducing the size or number of components. All these options, thought reasonable for a new structure, are unacceptable for historic preservation projects. We cannot apply the same materials and techniques to every building. Each historic building is unique, important, and irreplaceable.
In the above example, the architect failed to include a thorough conditions assessment early in the project. The goals of this assessment would have been to identify the cause of failures - not just the symptoms - and to produce detailed recommendations, including formulas and techniques for conservation and repairs. All this information would have become part of the bid documents and conservation contract. There should have also been more collaboration between the architect and the contractor, and their communication should have started earlier in the process.
There needs to be a fundamental shift in the understanding of architects about their role in preservation projects. Their role is to use their considerable talents to aid and guide the stewardship of our historic buildings. It is most important that they provide a means and structure to make this possible. This needs to be a building-centric not an ego-centric process.
Investigation and Treatment Process and the Architect's Role
The correct role of the architect starts with a commitment to the idea that the building is an artifact and needs to be preserved. Beginning the project with a preliminary investigation, the architect needs to bring in materials specialists to help determine the construction history of the building and the condition of the materials. The architect and the conservators then evaluate the conditions and jointly recommend treatments, and develop new ones when no standard methods fit the given conditions. The architect and the investigation team should try to understand the building.
Returning to the hypothetical stuccoed building, the architect and the investigative team should have tried to discover why the stucco was crumbling. It would have been important to know how many different stuccoes there were, where they were on the building, what their condition was, and what they were made of. Were they all deteriorating? In what different ways were they failing? How did the areas of failure relate to the rest of the building? Were there common underlying causes?
General Rules for Conservation Projects
Begin each project with a sense of respect and inquiry. Create a process that serves the building and does not work against it. In this way, the building has a chance to reveal its secrets and tell what it really needs. What is best for the structure will remain a central question for the duration of the project. Understand the history of the construction of the building. This is important because all the elements of the building are interrelated and interconnected; their conditions affect each other. Expect to continue to learn from the building as the work progresses. Evidence of past changes to the building and telltale markers of ongoing deterioration will regularly turn up. There must be a practical means of recognizing new information, evaluating its significance, and integrating it into the work schedule as needed.
Assess the condition of all the building elements, relating symptoms with their underlying causes. It is sometimes necessary to infer from symptoms - discoloration, peeling, cracks - what the underlying causes are. As a fuller picture begins to emerge, specific tests can be used to develop an understanding of the actual conditions. Understanding the chemistry of the materials is necessary to be able to predict the effects of new materials on the building. Recommended treatments should stabilize the building while causing as little disturbance as possible.
Decide what really is important. If funding is insufficient to complete the project now, plan to address the most critical problems and extend the schedule. Additional time means more opportunities for fund raising. Do not cut corners and destroy the building just to complete the work for an arbitrary deadline. Planning
Create a management plan that recognizes the different nature of this work. Materials experts, experienced conservators, and other specialists need to be part of the team that plans the project.
Perform as much investigation as the budget will allow prior to setting the initial project scope. Recognize the importance of investigation: budget for it and make room in the schedule for it. This early investigation lays a sound foundation for the work that follows.
Plan and budget for supervision. The discovery process continues during all phases of the project. Someone on site needs to understand the big pictures as well as the little ones, all of the time.
Create room in the budget for the unknown conditions. The cost structure has to include room for unknown conditions to be dealt with responsibly when they are uncovered. It should be anticipated that discoveries will be made as the project progresses and that as these new conditions are revealed, the scope and details of the work may need to change.
Cash flow is absolutely critical. Before the job starts, determine the nature of funding, who controls the money, and what procedures are required to spend it. The funding process must be designed to match the unique aspects of the conservation process. Failure to secure a workable solution can seriously limit the effectiveness of the conservation process.
Do not change the structure on which the project was bid once it gets underway without considering the consequences.
The Role of Conservators
The conservator should be asked to help define the building's problems and to come up with solutions early in the project. In this early stage the architect should have the critical condition assessments and treatment options provided by a competent conservator. If the conservator is brought in later in the project, when so much of the work has already been established, the conservator's ability to preserve important parts of the building is limited.
Building conservators must be building savvy. They must have knowledge of the trades and be skilled and experienced in organization, as well as tool and scaffold usage. They must know what is expected in scheduling and lead time. They must be able to collaborate with others in ways that lead to good solutions. If they cannot work comfortably alongside the craftspeople on the job and are unable to teach others, learn from the job, or make timely decisions, they will be like a stick in the spokes. Their role will become diminished.
The treatment processes developed by conservators must be feasible on a large scale. Conservators often fail to understand that if this does not happen, their treatment cannot be effectively carried out and will most likely fail. Their discoveries need to be tested on larger and larger building elements, the processes need to be scaled up and refined, practical delivery systems need to be developed, and people need to be trained to reproduce the treatment process.
New and untried treatments must be tested and proved right for the building's problems before the project gets underway.
The following are meant as general rules for mangers at all levels of a project. Obviously, depending on the type and size of the project, the management hierarchy would determine the roles of different managers.
Designate a project manager/supervisor/liaison person who has broad and extensive experience. Ideally, this should be someone who has been promoted from a shop floor-level position. Having too many supervisors is usually not workable except in special cases.
The project manager must be at the site.
Empower managers with the big picture. Managers need to understand how the time and costs for various tasks are derived and to be able to measure progress, make realistic schedules and shifts in resources, and have realistic expectations.
The managers should be included in the design of the project. They need to understand the overall plan, schedule, and budget, not only theoretically - as numbers on a piece of paper - but also how they were developed and what assumptions and approaches decisions were based on.
Contractors and Artisans
Assemble a team of highly skilled and cross-trained mechanics who enjoy the different pace and problem-solving aspects of the work. They must have all of the standard building trade skills as well as an understanding of how the building was constructed and how conservation is different from repairs.
Companies do not have skills, people do. Do not forget this. Highly specialized skills are required in conservation projects. Companies are selected to do the work based on their performance on previous projects and their reputation, which is established by work in the past. The quality of the work on these projects was no doubt due to the work of a few key people. Identify those people and insist that those people will be working on this project.
Perfect Treatments By Using Drops
What is really required to treat and conserve the building can be tested and perfected in one or more drops. An area of the building that represents a typical cross section of conditions, but not necessarily the most prominent face, is selected. After proposed treatments are bench, shop, and laboratory tested, they should be tried in this area, which is known as the drop. One example of a drop is a ten-foot wide vertical section of a building's exterior, running from cornice to grade.
The first drop is usually carried out by the conservators to scale up the treatment processes and evaluate results toward adjusting the final recommendations.
It is most likely that conservation and repair techniques will not be familiar to most contractors, and it is not advisable to have them experiment on the building fabric. Experience has shown that it is impossible to use specifications alone to teach techniques. The contractors and crew should be trained by the conservators on a second drop.
A more exact sequence of treatments, quantities of materials, tooling, and logistical requirements can be developed during the second drop. Treatments can be carried out until they achieve satisfactory results. Often, significant improvements in the treatment processes are discovered by the artisan and conservator team.
The second training drop is essential if the contractor is to arrive at a realistic budget and schedule. If these techniques are beyond the contractor's experience, it allows for understanding what is required in time, labor, and materials to carry out these treatments for the rest of the project.
The completed drops act as benchmarks for the remaining work, setting unambiguous standards for the quality of workmanship to be achieved.
Drops can be used to educate clients and sponsors.
Drops can be documented (film, video, text) for use in producing specifications for bid documents.