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Preserving Historic Buildings[1]
Protecting historic buildings is a challenge, but performance‑based design concepts can help make the twin goals of historic preservation and reasonable fire protection a reality.
William E. Koffel, P.E.[2]
Many codes note
that historic structures under construction or being repaired, altered,
enlarged, restored, or relocated needn't comply with the code provisions.
However, the authority having jurisdiction (AHJ) must determine that the
building is reasonably safe and doesn't constitute a serious life safety
hazard.
Although
proposed changes have been submitted to include specific language for historic
buildings, NFPA 101®, “Life Safety Code”, doesn't contain specific provisions
for them. However, the AHJ may modify the code when it isn't practical to bring
a building into compliance with code requirements, as long as the level of life
safety already provided is reasonable. Conditions that represent a serious
threat to fife must be mitigated, but the code allows some latitude in nonlife-threatening
situations because more effort and money may be needed to correct the physical
limitations of an existing building than the increase in life safety would
warrant.
Although people
think that performance-based codes apply only to new construction, historic
buildings present a perfect opportunity to apply performance‑based design
approaches to fire protection and life safety. While those who preserve
historic buildings want to maintain their historic characteristics, they also
want to provide a reasonable level of life safety, protect property, and
minimize disruption to operations.
All
historic structures have features worth preserving. In the United States, a
good example is exterior doors in buildings from the Colonial period. Modern
codes generally require that such doors swing in the direction of egress
travel. However, this wasn't the case in Colonial America, and reversing the
door swing will not only alter a historic characteristic, it could even create
hazards if it results in a change in elevation outside the building.
To
maintain a structure's historic characteristics, designers must be able to
document that the structure provides a reasonable degree of life safety. For
example, they may be able to calculate safe egress times to demonstrate that
even though a door swings inward, it doesn't constitute a serious life safety
hazard. Or they may be able to use design fire scenarios to demonstrate that a
historic building's interior finish materials don't contribute to rapid fire
growth.
A historic building might
also be brought into compliance by imposing operating restrictions on its use,
such as limiting occupant load. Where restricting occupant load isn't practical
or doesn't result in code compliance, other restrictions may be imposed. In one
building in which the door swings inward, the guide is required to announce
that the doors swing inward before a reenactment of a Colonial‑era trial
and to stand by the door during the reenactment.
Fire
protection systems may also be installed to compensate for architectural
features that aren't consistent with modern codes, such as open stairways.
Using computer fire models and other analytical tools, system designers may be
able to demonstrate that problems such as egress deficiencies aren't a serious
life safety hazard in buildings that have reliable fire protection systems.
It's
often easier to install a fire protection system properly than it is to correct
existing deficiencies, especially where the “deficiency' is historically
significant. And installing fire alarms and sprinklers in buildings constructed
before such technology became widespread is widely perceived as a means of
preserving the structure for posterity. However, such systems should be installed
carefully to avoid damaging the building's fabric and to minimize the aesthetic
impact on its architectural and historic features.
Additional requirements for protecting historic buildings can be found in NFPA 909, Protection of Cultural Resources, Including Museums, Libraries, and Historic Properties, and NFPA 914, Recommended Practice for Fire Protection in Historic Structures.
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