Timber frame fire findings

The London Fire Brigade have come back to me with the summary report of their findings on the Colindale fire on Wednesday 12 July 2006. Highlights include:

• The building was under construction and consisted of a concrete ground and first floor, with the remaining five upper floors solely constructed from timber.

• A fire was first seen at first floor level in Block B4. This is thought to be the fire’s ‘Area of Origin’. Block B4 was part of an ‘L’ shaped building with maximum dimensions 38 metres by 60 metres. The fire’s ‘Area of Origin’ was close to the centre of the building adjacent to the staircase shaft and lift shaft.

• The fire spread rapidly through Block B4 with full involvement and collapse of this building in less than 10 minutes.

• The fire spread by radiated heat to an adjacent building also under construction. The fire also spread via radiated heat to the top floor and roof of the neighbouring Middlesex University Halls of Residence. There was also damage by radiated heat to thirty vehicles parked in Aerodrome Road and to the “P.N.C. Building” located in the Hendon Police College on the opposite side of Aerodrome Road.

• As a result of the fire approximately 180 construction workers were evacuated from Block B1 and Block B2 and approximately 100 students were evacuated from the Middlesex University Halls of Residence. In addition, an unknown number of staff were evacuated from the Hendon Police College complex. No injuries were sustained during the evacuation.

And as to cause? The report makes these comments:

• The most probable source of ignition of this fire was a carelessly discarded lit cigarette at first floor level in Block B4.

• The rapid fire spread was not due to an accelerant and was consistent with the fuel present, i.e. High surface area compared to mass of construction timber, eighteen metres high with virtually unrestricted airflow.

Further thoughts and speculation

The key word here is accelerant. If there was an accelerant used (i.e. petrol or even paper), then we have a case of malicious arson. The report is quite clear that no accelerant was used. But my first thought was: How the hell can you tell anything about the cause of a fire, if the building has been burned to a crisp in just ten minutes? And why the speculation about a discarded cigarette? Presumably no one has come forward and said “Oh yes, I dropped a fag in B4 just before the fire took hold.” We would have heard. And unless there was a lot of readily combustible material lying around, like plastic sheeting or waste paper, a cigarette would not cause a timber frame building to catch fire. Whilst the fire spread may be consistent with the fuel present (i.e. timber and foam-based insulation), the initial ignition of the fire is more problematic. There surely had to be some intermediary element that could transfer fire from a lighted cigarette to a timber wall. That doesn’t necessarily mean it was a deliberately placed accelerant, of course, but there must have been something easily ignitable present and what that might have been isn’t mentioned.

Finally, it appears that there were builders on site but they were evacuated from buildings BI and B2, not B4 where the fire broke out. This suggests that B4 was quiet. That’s handy. And if you wanted to set fire to a block of flats under construction, where would you go about starting it? The fire's area of origin was on the first floor close to the centre of the building adjacent to the staircase shaft and the liftshaft. At the bottom of a staircase and liftwell? Just the spot to turn a small fire into a conflagration in seconds.

It’s enough to make you wonder, if nothing else.