When buildings are constructed or modified, they must adhere to rigorous fire safety regulations to protect the inhabitants for the lifetime of the building. The rules can be found in the Building Regulations, Fire safety: Approved Document B.

A key part of those regulations is about stopping fire and smoke spreading quickly from room to room in the event of a fire. The slower it spreads, the more likely it is that inhabitants can escape, and that firefighters can arrive at the scene to tackle it.

Ceilings are part of that protection. If there’s a fire in a living room downstairs, flames, heat and smoke will quickly reach the ceiling, and will eventually spread to a bedroom above. That’s why ceiling plasterboard is fire-rated. Basically, each 12.5mm should retard the effects of fire for 30 minutes. The risk will be factored into the design of the building and any fire safety assessment that has taken place.

The risk posed by downlights

That brings us to downlights. When they are recessed, i.e. flush with the ceiling, a hole needs to be made in the plasterboard to accommodate the fitting and the bulb. It’s not hard to see how in the event of a fire, plastic fittings could melt or ignite, and fall to the ground – leaving a series of holes around 70mm in diameter dotted around the room. Larger clusters of lights will leave even larger holes. Straight away, the 30, 60 or 90 minute rate rating of the ceiling has been compromised by these recessed luminaires.

Fire rated downlights are engineered to ensure they can withstand the effects of fire for as long as the rating determines. That tends to be 30, 60 or 90 minutes, but fittings are available that can last 2 hours for specialist cases. In essence, they should perform just as well as the plasterboard itself.

These fittings use a range of measures to ensure they keep the ceiling sealed. This includes the choice of materials, means of attaching to the ceiling and the use of intumescent materials in the seals. These materials allow airflow and heat dissipation in normal conditions but expand when hot, which helps keep the hole sealed.

If you’re installing downlights in 12.5 mm plasterboard, you probably only need fittings rated at 30 minutes. After all, there’s little point installing downlights that outlast the plasterboard. If you encounter thicker board, that has probably been determined by the original builder or renovator to be the correct thickness for fire rating purposes, so it’s wise to mirror that thickness with your choice of downlight fitting.

Homes, in general, are not especially good at containing fires. They don’t really have fire doors, as you’d find in public spaces and workplaces, so fire can spread sideways and up stairs relatively easily. That’s why the ratings for ceilings and light fittings in most domestic properties are surprisingly low. Energy is usually better spent on fire prevention, smoke detectors, escape routes, extinguishers and evacuation plans than stopping flames from spreading up through a ceiling, although 30 minutes’ protection is certainly helpful.

The good news is that most old homes and all new builds now have LED downlighting rather than halogen, which was the norm until the 2010s. Halogen lighting could easily exceed 200 °C, which is a fire hazard in itself. LEDs operate at around 25°C, which might be cooler than the room itself!

Downlights in top-floor ceilings

Although there’s obviously a risk of fire spreading into a loft, the regulations are more relaxed for top-floor ceilings, as they are focused on protecting people living above burning rooms. If the loft is uninhabited and unconverted, you’ll generally find that the rating is the minimum, 30 minutes. That said, there’s no harm (except financial) in being too safe, and exceeding the minimum demands of the Regulations, and many builders will recommend at least 60 minutes’ protection. Saving the roof makes a huge difference to the viability of a rebuild in the event of a fire.

What about surface-mounted downlights?

If you’re placing surface-mounted downlights, you probably don’t need to worry about fire ratings. Yes, you’ll be making some small holes in the ceiling for screws and wiring, but it won’t be enough to make a huge difference to its integrity. 

False ceilings under concrete floors

In most modern apartment buildings, each unit is self-contained. Concrete floors separate each flat from its upstairs and downstairs neighbours, rather than timber beams and joists as per the traditional manner. Concrete is very good at containing fire. However, if the owner wants recessed downlights, it isn’t possible to set them into the concrete above. Apart from the sheer amount of labour, there’s a danger of exposing or damaging the reinforcement. So the only option is a false ceiling, hanging a few centimetres from the real one.

In such cases, the plasterboard is largely cosmetic, and probably has a minimal fire rating itself, so there’s no need to use specially fire-rated downlight fittings.

Further reading

If you’re concerned about the fire rating of a ceiling you’re installing downlights into, it’s a good idea to check the Electrical Safety First website, which has a section devoted to downlighting. Download their PDF, which covers electrical safety more broadly, but does have plenty of valuable information about downlight regulations.