If a shaft enclosure connects less than 4 stories, what is the minimum fire-resistance rating required?

The minimum fire-resistance rating required for a shaft enclosure that connects less than four stories is one hour. This is based on building codes and fire safety regulations, which are designed to ensure that such enclosures provide a sufficient level of fire protection for the duration necessary for occupants to evacuate and for firefighting operations to begin.

A one-hour fire-resistance rating indicates that the materials used in the shaft enclosure can withstand the effects of a fire for one hour, thus providing critical time for emergency response and reducing the spread of fire within the building. This level of fire protection is typically adequate for structures of this height, where the risk is generally lower compared to taller buildings.

In contrast, higher fire-resistance ratings such as two, three, or four hours are required for shaft enclosures that connect more than four stories, as these scenarios involve a greater potential for fire spread and increased occupant load, necessitating stricter fire protection measures.