How Is a Commercial Fire Alarm System Designed?

A fire alarm system that has been designed for the wrong building, or for the building as it used to be, can leave gaps or generate avoidable false alarms. Design is the stage where those problems are avoided.

Start with the building and its use

A designer needs to understand what the building is, who uses it and how. Sleeping accommodation, a school with young children, a warehouse with high racking and an office with an open-plan floor each raise different questions. The fire strategy or fire risk assessment sets out what the system is meant to achieve, and the design follows from that.

Choose the category and type of system

For non-domestic premises, BS 5839-1 (current edition BS 5839-1:2025) describes categories of system, for example systems to protect life, systems to protect property and manual-only systems. The designer proposes a category, explains the reasoning and confirms it with the person responsible for the premises.

There is also a choice of type. A conventional system groups devices into zones, so the control panel tells you which zone has activated. An addressable system identifies each device individually. Larger or more complex buildings usually benefit from addressable systems, but this is a judgement for each building rather than a rule.

Lay out the devices

The designer works from drawings and the survey to decide where to place:

Smoke, heat or multi-sensor detectors, chosen for the environment (kitchens, plant rooms and dusty areas need particular care)
Manual call points at exits and along escape routes
Sounders and, where needed, visual alarm devices, so the alarm can be heard or seen throughout
The control panel and any repeater panels, in a location that suits the people who will use it

Consider interfaces with other systems

Fire alarm systems sometimes need to trigger other equipment: releasing magnetic locks on doors, shutting down ventilation, or interacting with lift controls. These interfaces are assessed case by case and agreed with whoever is responsible for each system. For access control, see access control systems.

What you get at the end

A specification describing the system and its category
Drawings showing device positions and cable routes
A schedule of equipment
A record of assumptions and variations

What a designer needs from you

Floor plans and building details
The fire strategy or latest fire risk assessment
Any insurer, building control or licence requirements
Details of any existing system that is being replaced or extended

If you want to see how this works in practice, see our fire alarm design page.

This article is general information, not advice for a particular building. What a building needs depends on its use, fire strategy, risk assessment and the requirements that apply to it. Standards are revised from time to time, so check that you are working from the current edition.

Related service: Fire Alarm Design

Frequently Asked Questions

How long does fire alarm design take?

It depends on the size and complexity of the building and how quickly the information is available. A small single-storey unit is a much smaller job than a multi-storey building with several tenants. We will give you an estimate once we know what is involved.

Can I use the design for tendering?

A design specification and drawings can usually be used to obtain comparable quotations, but check any terms that apply to the design and agree this at the outset.

Do I need a fire risk assessment before a design?

A fire risk assessment or fire strategy is the usual starting point, because it sets out what the system is expected to achieve. If you do not have one, the responsible person normally arranges it separately. We do not carry out fire risk assessments as part of this service.

What if my building changes after the design is finished?

Tell us. A change of use, a new partition layout or an extension can affect detector positions and the category of system required. We will say whether the design needs updating.