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Fire Compartmentation and Separation Basics

Fire compartmentation is about buying time: slowing fire and smoke so people can escape and firefighters can work.

Fire compartmentation divides a building into sections separated by fire-resisting construction. If a fire starts in one compartment, the construction is designed to hold it there for a period, giving people time to escape and firefighters time to act. It's a core principle in building codes worldwide.

How compartmentation works

Compartments are bounded by fire-resisting walls and floors. Openings in them, such as doors, ducts and pipes, must be protected so the compartment boundary isn't weakened. Shafts that pass through compartment floors, such as stairs and lifts, are usually enclosed with fire-resisting construction.

Terminology

• In the US, the IBC uses terms such as fire walls, fire barriers, fire partitions, horizontal assemblies and smoke barriers, each with defined requirements in Chapter 7
• In England, Approved Document B uses terms such as compartment walls, compartment floors and protected shafts, along with cavity barriers for concealed spaces
• In the UAE, the Fire and Life Safety Code defines its own separation requirements

These terms aren't interchangeable, so use the language of the applicable code.

What sets the requirements

Compartment size and fire resistance depend on factors such as:

• Building use
• Building height
• Whether the building is sprinklered
• The fire strategy, especially for complex buildings

What to show on drawings

• Compartment and separation lines on plans, with ratings
• Protected shafts and stairs
• Fire doors and their ratings
• Fire dampers or duct protection, coordinated with MEP drawings
• Cavity barriers in concealed spaces where required
• Head and junction details for fire-rated walls

Penetrations and fire stopping

Every service penetration through a compartment boundary needs suitable fire stopping. Coordinate with MEP engineers and specify tested systems for each penetration type.

Concealed spaces

Fire and smoke can spread through ceiling voids, raised floors and wall cavities. Codes may require cavity barriers or fire-stopping in these spaces. Show them clearly on drawings.

External fire spread

Fire can also spread between buildings or up a facade. Codes address boundary distances, unprotected areas and external wall materials. These rules can significantly affect facade design.

Coordinate with the fire engineer

Construction quality

Compartmentation only works if it's built correctly. Clear details, inspections and records of fire stopping are essential.

1. 01How compartmentation works
2. 02Terminology
3. 03What sets the requirements
4. 04What to show on drawings
5. 05Penetrations and fire stopping
6. 06Concealed spaces

Keep a compartment drawing set

Many teams maintain a dedicated set of fire strategy plans, separate from general arrangement plans. It keeps compartment lines, ratings and fire doors clear, and makes reviews and handover easier.

Compartmentation is a quiet but vital part of building safety. Accurate drawings and careful coordination help make sure it works when it's needed.

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