Fire resisting walls, floors and ceilings and fire-resistant glazing

Question 1

Describe how composite floors are constructed and explain how this effects how they
behave in fire. (4 marks)

Answer 1

Composite floors generally consist of a profiled metal deck with a poured concrete topping which can
perform differently in fire, because the metal base will conduct heat from fire laterally, and in so doing
the metal face will attempt to expand.
The rate of temperature increase in the critical parts of the floor may be lessened compared to
concrete alone, however the composite floor will also be fixed through shear connectors to the
supporting steel structure.
During the fire, steam formed in the concrete may force out the metal decking, distorting it and
causing gaps and subsequent failure, and whilst the steel reinforcement will transfer the load and the
heat from fire, the composite structure may ultimately deform under the heat and sag under the load
of the concrete.
The fire performance of all floors can be enhanced through the use of added passive fire protection
systems, appropriate to the floor type.

Mesh or fibre reinforcement to concrete

Question 2

Explain why active fire curtains may be used to provide compartmentation and give two
examples of locations where they may be used. (4 marks)

Answer 2

Fire curtains are particularly useful in open-plan spaces or where permanent barriers (like walls or doors) are impractical, offering flexibility in design while still meeting fire safety regulations.

• Atriums
• Lobbies and receptions
• Boundary protection (external)
• Openings in walls
• Compartmentation
• Stair wells
• Lifts
• Escalators

Question 3

a) Explain the purpose of compartmentation. (2 marks)
b) Describe four factors to be taken into account when determining and installing fire
protection for compartment walls. (4 marks)

Answer 3

A fire wall is a separating element found in various locations throughout a building. A fire wall is
designed to restrict the spread of fire for a certain amount of time from one side to the other. They
are used to compartmentalise, and sub divide buildings and are also used to enclose areas of special
fire hazards and protected escape routes

In the majority of cases a fire wall will be required to perform in either direction of fire attack and will
therefore often be symmetrical in design.
They may be loadbearing structures dependent on location and are in most cases required to provide
structural stability for the required fire period while also providing integrity, insulation performance.
Fire walls may be incorporated to separate production and storages areas, or to isolate specific areas
of production that may be considered a high risk, or simply areas used for different purposes.

Compartmentation fire performance
The degree of fire resistance required will depend on several factors including:
* The specified fire resistance period
* The height of the top floor above ground and the intended use known as the purpose group
of the building
* Whether fire resistance is expected from one side or both sides of the barrier
* The type of fire performance required i.e. stability, integrity and insulation

Question 4

a) Describe how non-fire rated glass behaves in fire. (2 marks)
b) Explain what is meant by “integrity only glazing” and give two examples of this type of
glass. (3 marks)

Answer 4

In a fire situation, non-fire rated glass will not be able to tolerate the thermal stresses generated from
the heat of the fire (which could be at temperatures of less than 100°C), leading to multiple cracking
resulting in the glass falling out of its frame in a matter of minutes.
This situation can be amplified if the thermal shock generated by water from a firefighters hose or the
activation of a sprinkler system were to impinge the hot surface of the glass.
Furthermore, in situations where security is deemed a critical issue, toughened (also known as
tempered) glass will often be considered appropriate. However, in fire conditions such glazing is
subject to catastrophic failure.

Integrity only glazing is glazing that offers integrity but has no insulation or limited heat radiation properties.

types of integrity only glazing are:

• Wired glass
• Laminated float glass with intumescent or char promoting interlayers
• Modified toughened glass
• Borosilicate glass
• Glass ceramic
• Those using various types of non-insulating organic interlayer technology