Restoration vs. Preservation:
Is there really much difference?
This letter came about as part of some questioning on a project where our report and proposal were radically different than the thirteen preceding approaches. There was a lot of question from the county about how that could be and this was our initial response. We thought it might be useful as an overview of the differences between the two approaches - both goals and outcomes.
I've been thinking about the project and the comment that has been made to me several times about "How could two companies with the same background and experience come to such different conclusions?" I realize that there is a basic misunderstanding here that needs to be addressed. The contractor for this project has been in business a long time and is a respected restoration contractor. Restoration contractors tend to specialize in work on older buildings and repair them by replacing and rebuilding parts of them.
I work in a different field, the field of architectural conservation. We work from the premise that the building is an important artifact and so the goal is to save all original materials, much as you would with a rare old master painting or piece of antique furniture. I work with a team made up of architects, engineers, conservators, craftsmen and material scientists. Our focus is on understanding the intent of the original builders ( how the building started out), the nature of the original materials, and the deterioration processes that have occurred, toward the development of methods and materials to reverse damage, stabilize fragile elements, and preserve the building elements. This is a relatively new field that has been developing slowly since the 1972 Williamsburg Conference that brought together for the first time in this country museum conservators, material scientists, architects, and engineers.
The processes used for conservation and restoration are very different. Throughout most of the
twentieth century, restoration has been carried out using the standard approach for designing and
constructing new buildings. This is: an older building is examined, its damage and failure
symptoms noted, and much attention paid in the design phase to its next intended use
bilitation to meet modern needs). The repair approach focuses on addressing obvious
symptoms, i.e. peeling paint and cracked plaster or cracked and shifted jack arch bricks (i.e.
surface appearances). These are dealt with in the specifications by instructing the contractor to
remove the failing material and replace with similar materials. On the whole, the approach is to not
trust the original materials but replace with known modern ones (whatever the contractor is used
to doing). A good example of this is the replacement of rotting wood lintels over windows with steel
beams. In other words, use only materials and techniques that are off the shelf and familiar to any
contractor. So the decisions are made before the project begins, specifications are written,
drawings are produced, and the building is cut to fit the new design. The process moves in one
direction as shown below:
Assessment >> Design >> Specifications >> Contractor Bid >> Work Begins >> Building Complete
This process is designed to reduce risk for everyone (except the contractor who must decide how far to take the repairs as he will be ultimately responsible if anything original that is left behind subsequently fails) and to produce a new-old building. In the rare occasions where specifications state that preservation of original materials is important, they rarely provide any proven roadmap of how to get there. They often are contradictory in tasking the contractor with preservation while penalizing him for any failures down the road. The net result is that the safest course of action when in doubt is to continue to replace original portions of the building with new materials.
Anyone who has worked on an older building knows that the minute you begin, new problems are encountered and new discoveries are made. The linear approach used for new construction has no place for these new conditions and no feedback loop or process is in place to respond to them appropriately. Usually not much attention is paid to the underlying causes of failure and there is seldom much recognition of the complex and damaging intersections that occur a few years down the road when the new materials interact with the old. Going back to the example of replacement with steel beams over windows, this steel contracts and expands much more than the original wood, pushing the bricks, opening cracks that take in water, and ultimately corroding from water inﬁltration, leading to even greater expansion of the steel and damage to surrounding masonry and windows.
With the restoration process, much of the original fabric of an old building is cut away to fit the current solution and less and less of the building survives. This process of design and upfront decision-making works well for designing new structures, but works against the goal of preserving the original architecture; the building we are supposedly tasked with saving.
The conservation process is different in that it starts with the assumption that the original materials are to be preserved and that it is our job to respond to the needs of the building. This initiates an holistic investigation into all aspects of the building from the original design and intent, through the changes and alterations over time and repairs on top of repairs. This insight into the complete history is accomplished by forensic aboveground archaeology. Materials can be dated and put into sequence by understanding their chemical and physical properties, the technology used to manufacture them, and their position in relation to other elements. As the conditions are assessed, a full picture is developed of what happened, when and why. There is rarely only one source of decay that results in the damage that initiated the project, but rather several sources, often including a series of ill-conceived attempts to fix or cover up the offending appearance that has instead led to deeper, hidden problems. It is important to suss out all of the interrelated conditions that will renew their damaging processes even as the repairs are being carried out. Because the conservation approach seeks to rectify all of the sources of deterioration, keeping us from continuing to make cosmetic rather than substantial repairs, in the end it is often the cheapest solution, in addition to saving most of the building.
One important and often misunderstood difference between restoration and conservation is the recognition within conservation that original structural systems that have done well for centuries should be kept in service - once the more modern materials or treatments that have threatened them are removed. Thus we approach buildings from the perspective that on every construction project something can usually be done better, so we should figure out where an historic building's structure could be augmented a bit. We do not start by rejecting the empirical knowledge and skill of our forefathers, but rather recognize they still have much to teach us. This is a recognition that the majority of modern treatments have repeatedly proven incompatible with older building systems which are grounded in entirely different building technologies. As impressed as we are with our modern technologies, our buildings have yet to prove themselves over time.