Does a mezzanine floor need fire protection?
It depends on how the mezzanine is used, how big it is and how far people are from an escape route. Office and public mezzanines nearly always need fire protection. Small storage mezzanines often do not. Many approvers use rules of thumb such as the mezzanine covering more than half the room, or exceeding around 400 m², as points where protection or extra escape measures are expected, but Building Control decides on each design.
What decides whether fire protection is needed?
Three things. Use: people working on or under a mezzanine raise the requirement. Size: a large mezzanine, or one covering a big share of the room, behaves more like a separate storey. Escape: the distance from the furthest point on the mezzanine to the top of a stair, and how many stairs there are, must suit the guidance in Approved Document B.
Your building matters too. Existing sprinklers, detection, compartment walls and the fire strategy for the whole building all affect the answer.
What does mezzanine fire protection involve?
Typically a tested fire-rated ceiling fixed under the joists, fire-resisting board casings around the columns, and a fire-rated fascia along the open edges, giving 30 or 60 minutes of protection to the structure. Detection and alarms are often added, and sometimes sprinklers under the deck.
Every hole through the fire-rated ceiling for lights, cables or pipes has to be sealed with a tested fire-stopping product, which is why fit-out and fire protection need coordinating.
Can I avoid fire protection by keeping the mezzanine small?
Sometimes. A compact storage mezzanine with a stair close to every part of it may not need protection. Splitting a large mezzanine into smaller ones, adding a second stair or using an open grating deck can change the outcome. We test those options at design stage, but the final decision rests with Building Control.
What about existing mezzanines?
If you change a storage mezzanine into offices, or an insurer asks, fire protection can be retrofitted. We survey the existing floor and fit a tested system around it.
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More questions
Is a 60-minute rating always needed?
No. Many mezzanines need 30 minutes; 60 minutes is required for some uses and layouts. The fire strategy sets the period.
Do sprinklers replace fire protection?
Sometimes they change what is needed, but not automatically. Building Control and the fire strategy decide.
Who signs off the fire protection?
Building Control, as part of the mezzanine approval. Keep the installer's certificates for the fire-rated products.
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