void fire detection

Crouching Void, Hidden Hazard

Papering over the cracks won’t stop the spread of fire…

There is nothing more fascinating than uncovering something that you didn’t know was there.

You might, for instance, be taking out a fireplace during a renovation to find a bigger, original structure behind it. Or you could be peeling back old wallpaper to discover a cupboard or secret door in the wall…

But aside from the mystery and adventure, sometimes finding a secret crypt or hidden alcove in a building can have its downsides.

Fires in Voids

In construction terminology, a hidden space is a ‘void’ and this presents a lot of issues that can have serious implications, especially if the void doesn’t have the detection and protection that is required.

It’s worth noting that new buildings will have these, but older buildings typically have lots of nooks and crannies – and it’s these areas that should concern you the most.

The areas that constitute voids include:

  • Areas above false ceilings
  • Roof areas that span the length of the building or go across a building
  • Floor voids, such as the ones created to level up floors for ease of access
  • Blocked up cellars and shafts
  • Old dumb waiters and unused lift shafts
  • Covered over gaps between buildings

Period Properties Go Undetected  

One of the biggest risks in older buildings is the uncontrolled spread of fire throughout the building. Hidden voids provide a great route around the building, which fire is very adept at exploiting.

A hidden fire will gain quite a hold before being detected and the delay in detection can be deadly…

In the recent case of the devastating fire at the Royal Clarence Hotel (RCH) within the Cathedral Yard in Exeter, which occurred on 28th October 2016, the official report said:

“The fire spread undetected through voids and other channels throughout the hotel leading to the sudden development of the fire.”

The report details that the building was continually worked upon during its lifespan since 1769, having started out as local coaching inn and meetings room before accommodating the likes of Beatrix Potter, Thomas Hardy and Clark Gable in later years.

It’s not a surprise that fire safety and building regulations have changed since then. Rules and regulations are constantly changing – but what does this mean for the thousands of buildings that still exist?

We can’t go knocking down Grade II listed buildings because they don’t fit the new criteria…but equally we can’t let a thing like a hidden void bring it to ruin in the case of a fire…whilst simultaneously putting lives at risk.

These buildings are part of history and can even define the character of an area. They deserve our respect, admiration and – perhaps, most importantly – protection.

Another extract from the report explains how expansion of these older buildings can create further problems for void detection:

“Over years, heritage buildings have been subject to internal re-design as well as increasing the size of the properties by adding additional buildings to the footprint.  This has enabled the increased risk of hidden voids, old shafts, old materials to be covered with more modern building materials over the years.”

Find, Detect & Protect

1. Find them

First, you need to know where these voids are. A great place to start is to have some accurate drawings created as you’ll find the measurements which could explain a gap between two areas. You could ask the lovely people that work in the building to chip in with their own knowledge and you’ll be surprised at what they already know.

2. Detect within them

You can use air-sampling detection (better known as VESDA) within voids. VESDA is a single pipe, or network of pipes, which draws smoke into a box housing a laser smoke detector that literally counts combusted particles in the sampled air.

3. Protect them

You can install water mist suppression or sprinklers within voids. The RCH report is careful to point out the water damage pales in comparison to the loss of an undetected or suppressed fire.

You have to ask yourself: if I ignore these voids what will the cost of that be?

The bottom line is that you should be considering the void spaces within your building and taking actions to avoid the devastation that a fire can bring.

The cost of the fire safety work could be significant, but the cost of not doing it could be a disaster, and that would be far more significant.

All the best,

Paul Field

Chief Void Spotter

P.S. The report for the fire in the Royal Clarence Hotel  is available to read in full on the Gov.uk website.


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