Whether the job calls for rehabilitating a 1920s-era high-rise structure in a city's downtown or restoring a Founding father's estate to its original luster, historic preservation projects call for a great deal of expertise. A qualified contractor with the experience to handle the numerous challenges of an historic preservation project and the knowledge that each historic preservation project has the potential to be vastly different from the last project is a must.
On any historic project, the age, building techniques used, locations, materials and many other factors must be considered throughout the process. In addition, the history of construction is important to keep in mind. The most successful historic repair contractors often approach projects in the most conservative manner possible.
Areas of Concern
Over time, a structure will develop numerous problems. Perhaps one of the biggest enemies of an historic structure is water. Water infiltration is of particular concern with historic projects because the interior of the structure often has significant details such as ornamental plaster, art, mosaics, woodwork or other finishes that are irreplaceable or extremely expensive to restore. For example, turn-of-the-century masonry-clad steel-frame buildings that are exposed to water infiltration may exhibit signs of masonry clad bulging and/or severe cracking on the exterior -- a symptom of embedded steel corrosion.
In addition to problems caused by water infiltration, other key areas of concern include settlement or deterioration of materials. Often in older structures, key structural elements are in contact with the ground. For example, a wooden frame structure will often have a sill beam (or sleeper) that sits directly on grade. If the structure is not properly maintained; gutters regularly cleaned out, etc., water infiltration and rot, vermin infestation or biological growth may become a problem.
Consideration must be given to elements such as the roof, windows, walls, wood frame, mortar, and foundation. Additionally, depending on the structure's age, other issues can come into play. For example, terra cotta - a popular building material during the Art Deco era of the 1920s and 1930s - often exhibits deterioration and spalling due to freeze-thaw cycles and inappropriate maintenance such as caulking mortar joints in lieu of repointing. Foundations are another major area of concern in aging structures; foundations may have deteriorating mortar and displacement because of improper drainage or lack of maintenance.
Foundations are another major area of concern in aging structures. Stone walls and foundations may have deteriorating mortar (lime-based or otherwise). Mortars can present many other issues with one common trouble spot involving improper treatment or repair. Portland cement was introduced in the 1870s and it gradually became more popular than lime mortars because people were impressed by its great compressive strength. However, many contractors of the era did not realize it was unwise to repair a lime-based mortar with Portland cement. The latter did not allow the former to breathe, preventing it from self-healing.
Repairing lime-based mortars with Portland cement is an example of a mistaken assumption that new materials are always better. Using new products and materials on aging buildings can have the potential to counteract the original intent of the structure's design. However, new technology can and should be used in the appropriate way. When used to repair a historic structure, much research is needed and in-depth examination is required to ensure the intended results. For example, carbon-fiber technology is a new material that can be very useful for strengthening existing structures.
Expert Knowledge Critical to Success
One of the most common misconceptions about historic preservation is that it's the same as any other type of construction. Owners may believe they can work with any contractor, and contractors with experience in new construction may think historic preservation is simply a quick jump. However, working on existing historic structures is quite different from new construction. It requires expert knowledge of the history of construction and historic building materials.
For example, expert knowledge of historic building materials was critical to the repair of the University of Maryland's Davidge Hall in Baltimore. Davidge Hall was originally built in 1812 and stands today as the oldest anatomical hall in continual use for medical education in the English-speaking world. Time had taken its toll on the historic structure and, in 2006, Baltimore-based Structural Preservation Systems was called upon to restore Davidge Hall's 200-year-old windows and doors. The windows and doors had to be repaired and replacement portions needed to match the original in profile, substance and appearance, using as much original material as possible. The key to success for this project was the knowledge of both historic construction materials and methods; precision was essential. Some severely deteriorated muntins required replacement with a tolerance of 0.0001-inch while the original glass was salvaged and replaced. Dutchman repairs were employed where possible when material was missing or deteriorated, and no screws or metals were used in repairs - all pieces were dowelled and glued. The original wood species was identified and matched for the repair.
New Not Always Better
People often think, "Why should we keep this old structure when it may be easier to build a new one?" New construction often cannot replicate the structural benefits found in historic materials. Old growth lumber is more stable, more dense, and therefore stronger than new growth. It's also important that we preserve our nation's cultural and architectural heritage, not to mention resources. One of the first major historic preservation projects in this country was the restoration of George Washington's home, Mount Vernon, in 1858. Many generations have benefited from the educational opportunities of this preservation effort.
A common misconception is that it's more cost-efficient to tear down an old building and build a new structure. However, new construction - especially if the building is in a historic district - may fall under a set of building regulations that could have a financial impact on construction. A recent example when this misconception affected a project financially involves a building located in a historic district in Bel Air, Maryland. The building, not protected by historic standards, was demolished in order to build a new structure in its place. However, the property is located in a designated historic district, and the new building must match the district's strict design standards. The owner/developer is having a difficult time getting through the Town's permit and planning boards. In this case, it would have been much more cost-efficient to preserve and adapt the existing structure to its new purpose. Before a decision is made to tear down and build new, all factors must be considered carefully.
Select the Right Firm
Another key to a successful historic repair project is selecting the right firm. Owners should look for experienced, professional firms that take an individualized approach to projects. The following items should be considered: bond capacity, size and longevity of the firm, craftsmanship, a formal Quality Assurance/Quality Control program, as well as proven experience with projects on nationally or locally registered historic structures. Be sure to ask the contractor about their familiarity with the Secretary of the Interior's Standards for Rehabilitation and Guidelines for Rehabilitating Historic Buildings. Failure to adhere to these Standards could negatively affect Historic Tax Credits and could have a financial impact on a project. Finally, make an attempt to assess the contractor's communication skills. Is the contractor available and responsive? If the contractor isn't conscientious about returning phone calls when a potential client requests information, responsiveness isn't likely to improve as a project progresses. On a historic preservation project, good communication is particularly important.
About Structural Preservation Systems
Structural Preservation Systems is a division of Structural Group, one of the nation's leading specialty contractors. Structural Group's three divisions include Structural Preservation Systems, VSL and Pullman Power. Structural Preservation Systems is the largest specialty contractor focusing on structural repair, strengthening, preservation, and rehabilitation of masonry and concrete structures. VSL is the technical leader in post-tensioning and specialty reinforcement. And, Pullman Power leads the industry in chimney, silo, and stack construction, maintenance, and repair. From 26 operating centers around the United States, Structural Group businesses perform a wide range of projects involving industrial facilities, commercial properties, public infrastructure and municipal buildings. For more information about Structural Group, visit www.structural.net.