Darwin explained evolution as survival of the fittest. He was referring to animal life, of course. But another sort of natural selection process occurs with buildings. Over time, a community can become attached to a familiar building facade. It becomes an ingredient of the cityscape, regardless of what function is performed inside the building. It belongs to everyone and becomes permanent.
When the function of a building can be preserved along with its use, each succeeding generation can continue to use it as it was intended. What happens most often, however, is that the shell of the building stays fundamentally the same, while the function inside changes with time. Darwin would have approved.
Adapting and reusing
When the life of a building such as a school is finished, another life for the building is possible. Conversely, an abandoned historic building with a non-school use may have sumptuous quantities of space that could be used for a school. In either case, a new function must be found for an old form. The result usually is called adaptive reuse. Several distinct recurrent problems can crop up in the adaptive reuse of any old or historic building:
- Historical restoration
Because the building has a distinguished past, what normally are modest costs to repair a building can become excessive when they must be authentic to the period when the building was built. Replication of historical materials and details is expensive.
- Hazard removal
Older buildings commonly used asbestos in combination with various building materials. Where asbestos is discovered, special permits and expertise are necessary for effective mitigation. Mitigation for hazardous materials is costly and takes time.
- Accessibility
Providing access to buildings for all people often conflicts with historical-preservation issues. For instance, a grand entry stair might be circumvented by a ramp. Such a sloped or curved ramp rarely meets the detailing standards of the historic building itself.
- Energy conservation
Prior to the late 1970s, U.S. buildings paid little attention to energy efficiency. Single-pane windows were the norm. Traditional high ceilings mean a large volume of air to heat, cool or recirculate.
- Parking
For buildings of a certain age, the original design did not take motor vehicles into account. Those converting an old building often must set aside space for parking.
Structural safety
Accommodating structural loading has restrictions that can hamper the conversion of building use in major ways. Regulations in the United States pertaining to seismic safety are fairly recent. Once the structural capacity of a building has been revised to add space, the building may be required, by code, to meet new seismic regulations. Many older buildings are constructed of unreinforced masonry. In such cases, seismic bracing must be added to the building.
For low buildings such as schools, the major structural concern is the resistance of vertical loads. The materials that are used have weight that can be measured and are relatively constant. By researching historical records, one can approximate the variable weights applied to a building by nature, such as snow. The human use of the building is something like snow, in the sense that even within a specific use, the weight applied to a floor can vary according to use.
The extremes of load have to do with the number of people who can occupy the space, as well as the weight of furnishings and equipment that they use. The loading determination, therefore, usually is governed by the building code. The code applies the intended function to a space and supplies the engineer with the necessary estimated loading for design. When the use of the building changes, the code designation changes, and the allowable floor load also may change — sometimes in a prohibitive way. If a school, or a portion of a school, is to be converted into a library, for example, the entire floor support system may need to be replaced.
Human comfort and acoustics
The concerns for structural safety have to do with collapse or failure. But for human occupation, safety and comfort are the main factors. The question of comfort often includes deflection. When people sense that a floor is moving, they become alarmed. Their fear of collapse is activated, even though the structural strength is sufficient.
For example, trusses as a means of structural support always must be checked for deflection. Because they are materially a very efficient way to support load, they often contain slender members that are themselves physically light in comparison to the load they carry. As a result, truss deflection often exceeds that of solid beams. A truss may be used to span a roof (where people do not often go) but be insufficient to use as a floor because the deflection is too great for human comfort.
The acoustical qualities of a space also are fundamental to the successful conversion to or from a school. Although speech clarity can be improved vastly with the finishes on the floors, ceilings and walls, sound isolation often is a more difficult problem. The sounds of footfalls on the floor above can be a distraction. Inopportune location of windows also can mean the inability to open a window for acoustical privacy on a hot day. Sound also travels well through cracks in old buildings.
Loading up
Another manifestation of adverse structural considerations is the presence of columns. For reasons of efficiency, a structure often contains a grid of columns. When the beam spans are equal between columns, the depth of structure is more likely to be uniform. Uniformity of structure usually leads to construction economy.
When a structure is multistory, the loads on the columns accumulate vertically. Column loads on the top floor usually carry less load than those on the floors below. Engineers try to put columns where they will not be in the way of functional use. Therefore, they adopt a grid pattern that most likely will result in columns placed in walls, rather than freestanding in open space.
In a classroom or lecture hall, a column also can be an obstruction to view. In old wood buildings, the spacing of columns can be determined by the maximum size of available solid wood beams. The available length of lumber has changed in the last 100 years. However, with modern glues and lamination, almost any dimension of wood member is possible to duplicate. Columns can be removed from a space by replacing the interior columns with modern laminated transfer beams. When this is done, however, the transfer beam still has to be supported at its ends. Longer transfer beams also usually mean larger supporting loads at the beam ends and a larger column load that must be carried vertically down to the foundation. Changing the foundation conditions, or even reusing historical foundation conditions, is not impossible, but it is difficult and expensive. Because of this, for school use, one still usually seeks a building without column conflicts.
Space planning
With an appropriate column grid, walls conceal the columns. The result is space that has a certain shape and dimension. A classroom usually is a rectangle. An additional criterion that contributes to the successful use of a room as a class is the possibility of daylight and even cross-ventilation. The windows of a class usually are on the long side of the rectangle. Since most students are right-handed, the head of the class and blackboards often are placed so that the writing hand of the student does not cast a shadow on what is being written.
Now that computers are common in classrooms, the question of screen glare and placement of ceiling-mounted projectors have become issues in using the classroom space effectively. A building that is being considered for use as a school usually must have a number of rooms that can be used as classrooms successfully. Conversely, when a school is purchased for possible conversion to some other use, the new owner must have a use that is compatible with having numerous rooms roughly 750 square feet in floor area that have windows along one long rectangular side.
A corridor to serve the classrooms also is common in schools. When an older building is converted from another use to a school, the doors, halls and stairways often must be widened to accommodate a larger traffic flow. Elevator cabs might need to be renovated to deal with the increased chances of vandalism. Converting an old school can work well when there is a reduction of loads both from a circulation and material point of view. Schools often become housing for senior citizens. The accompanying expense for such a conversion is for the additional plumbing.
It should be clear that the adaptive reuse to or from a school requires two forms of vision: one for looking back at past use and the other for peering forward into future use.
Rush is an architect with The Office of Michael Rosenfeld, Inc., Architects in West Acton, Mass.