The Test of Time

Preserving historical school buildings is an art.

Many school buildings are more than 50 years old and have the potential to be landmarks. However, few schools of this vintage actually receive official landmark designation, which would protect them from inappropriate exterior alterations and repairs.

Over the years, weather and use take a toll on a building's facade. Often, this leads to failing roofs, masonry, parapets, structural steel, cast iron, windows, doors and hardware. In many cases, deferred maintenance or inappropriate upgrades have made conditions worse, and a building can lose its character-defining elements.

Whether a school is a historical landmark or simply an older building, an approach based on proven preservation methods can develop systematic solutions that treat existing materials appropriately. Over the long term, such a strategy will reduce maintenance costs and subsequent future major rehabilitation projects, and maintain the structure's integrity.

Do your research

Historical research is the first step when pursuing preservation or rehabilitation. This process unearths useful technical data on architectural conditions, material compositions and sources, and building systems. Information gathered during research will serve as the basis for on-site documentation of existing physical conditions.

Historical documents also are useful in tracking which modifications have been completed, as well as which building deficiencies are likely to recur. Gather the building's original plans, specifications and construction photographs prior to a field inspection. Although original drawings and specifications may not reflect the actual construction because of unrecorded field changes or substitutions, these documents are the basis for the visual inspection that will confirm, refute or augment the recorded information.

In the case of a landmark building, school officials should check with local or state public historic-preservation agencies, which already may have documented some of the building's history.

Existing conditions

A complete understanding of the building, its components and the deterioration process is essential. An existing-conditions survey should document the building's composition, configurations and as-built conditions. Using comprehensive documentation to evaluate existing conditions is the basis for developing a precise scope of work. This will lead to more accurate contract documents and bids. A survey also can help schools uncover unforeseen conditions before construction begins.

By assessing the historical record, inspecting the site and testing materials, a survey will document existing materials, construction assemblies and conditions. It identifies to what extent a facility has deteriorated and should uncover conditions that are hazardous or may lead to irreparable loss of features or finishes. This information can be used to stabilize, protect and repair a facility.

During a field survey, an architect also will quantify repairs. For example, rather than graphically indicating areas of the facade that require re-pointing and allowing bidders to estimate the area in square feet, the area should be quantified so all bidders can submit a unit cost.

Surveying the field

Field testing uses probes to examine concealed conditions. This can provide valuable information on the nature, causes and extent of building deficiencies. Field-testing methods can be invasive or non-invasive.

Non-intrusive or non-destructive techniques do not require openings or destruction of building materials. For example, metal detectors can find hidden or embedded structural members and anchors. Sounding with a rubber mallet is an effective way to identify areas of subsurface delamination of materials, such as terra cotta and stone. Water and air-infiltration studies can be used to find leaks in roofing systems and mechanical ducts, or through doors and windows.

Intrusive or destructive evaluations require openings or removal of building components. This type of testing might be required to determine the extent of corrosion on concealed structural elements or to document the configuration of structural anchors. Intrusive evaluation also can document walls and ceilings so that new building-system improvements, such as mechanical ductwork or fire sprinklers, can be concealed.

Invasive inspections are most useful in areas with evident distress, such as cracked stone or terra cotta with adjacent rust staining. These conditions indicate that embedded steel anchors have deteriorated. Removing damaged stone materials is prudent because extensive repair and replacement would most likely be required anyway.

During the field survey, samples of materials may be taken for laboratory analysis. The architect conducting the preservation survey should be able to perform several basic tests in-house, such as analyzing cleaning methods, mortar and paint. Laboratory testing determines specific material properties and identifies the probable reasons materials and assemblies have failed or deteriorated. Testing also can determine whether hazardous elements are present and contributing to the building's problems.

Identifying material properties also is useful for matching or replacement, as well as to project the future performance of potential repairs. Test results enable an architect to write more specific contract bid documents. For example, simple analysis of a mortar sample enables an architect to specify the constituents and their proportions rather than using vague language, such as “contractor must match the original mortar.”

Next steps

Based on historical research, an existing conditions survey, field testing and laboratory testing, an architect can outline options and cost estimates for rehabilitating or replacing each building facade system.

For older schools, the options typically include a range of solutions: window replacement may be recommended where the windows are not original, and window rehabilitation may be the preferred option where the windows are intact. The architect then develops a design and prepares construction documents. The plans should include a contingency budget and make it the contractor's responsibility to meet the schedule.

Cole, AIA, is director of historic preservation for Swanke Hayden Connell Architects, New York City. The firm worked on the P.S. 157 project (see sidebar on p. 45).

NOTABLE

Some aspects of a successful historic-preservation project:

  • HISTORICAL RESEARCH/DOCUMENTS
  • EXISTING-CONDITIONS SURVEY
  • FIELD TESTING
  • LABORATORY TESTING OF MATERIALS
  • OPTIONS/COST ESTIMATES
  • DESIGN DEVELOPMENT/CONSTRUCTION DOCUMENTS

A building for the future

New York City Public School 157, constructed in 1907 and serving grades K-3 in the Clinton Hill neighborhood of Brooklyn, is an early example of the work of C.B.J. Snyder, who designed many of the city's public schools at the turn of the 20th century. A limestone statue of Benjamin Franklin over the entrance and 40 terra-cotta owls at the parapet are reminders of the power of education. By 1999, the terra cotta, limestone, brick and ornamental copper had deteriorated significantly, and administrators took steps to make the building safe and serviceable.

Although P.S. 157 is not an officially designated landmark, the project team recognized the building's historical significance. It followed the U.S. Secretary of the Interior's Standard for Rehabilitation as the in-house criteria for design work. Where possible, historical materials were repaired rather than replaced. When budget and schedule made in-kind replacement infeasible, the project used substitute materials that replicated the original appearance and provided durability. Deteriorated or missing features were restored with the aid of historical photographs and original drawings.

Most of the parapet's terra cotta ornamentation, including the owls, had been removed. Water leaking through the roof had corroded the underlying structural steel and caused the ornamental terra cotta cladding to fail. The parapet had to be removed and reconstructed to replace the cladding, and to repair and replace the structural-steel members below. More than 6,000 new terra cotta units were fabricated to match the original, including replication of the missing parapet ornamentation. The roof and flashings were replaced with conventional roofing systems.

The balance of the brick, terra cotta and limestone facade was in fair condition. Inappropriate high-strength pointing mortars were removed, the entire facade was raked with hand tools, and compatible pointing mortar was installed.

Ornamental copper spandrel panels were repaired or replaced. The copper was cleaned with chemicals and waxed. Paint was removed from the terra cotta and limestone using products that would not harm the masonry surfaces. The limestone lower story of the building was coated with a clear anti-graffiti coating. The damaged limestone statue of Benjamin Franklin was restored.

To meet security requirements, the school installed custom steel doors with recessed profile panels to replicate the original doors.

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