At 5.07 pm on the 7th of November 2011, Gordon fire Station responded to a house fire in Turramurra. On arrival, firefighters were met by the owner and shown smoke coming from a window sill in the bathroom of the first floor. The window sill was removed and the timber and wall studs within the cavity were found to have deep charring. A CO2 extinguisher and water was applied and a Thermal Imaging Camera (TIC) was used throughout the remainder of the house, with no hot spots found.
Tpower had been turned off by the owner on arrival of the fire crew; however, when the power was turned back on, no circuits tripped and the electrical system was deemed sound. The fire crew remained in attendance for about 45 minutes and the cause of the fire was recorded as undetermined.
At 8.36 pm Gordon Station was responded to smoke issuing from the same house. Firefighters arrived to flames issuing from the roof, with ducting dripping onto the ground floor internally. Crews entered with a house line and reached the first floor when the ceiling started to collapse, at which time crews exited and firefighting was conducted from the exterior. The fire was extinguished after extensive damage was caused throughout both levels of the house, with approximately 50% collapse of the roof tiles.
Information from the owners was that a water pipe was pierced by a nail when trying to fix skirting in the bedroom adjacent to the bathroom. The water was turned off and a plumber was contacted to fix the leak.
He arrived around 1.30 pm that day and repaired the pipe. Around 5.00 pm the owner saw smoke coming from the bathroom window sill, where the paint was blistering. She called Triple Zero and firefighters arrived, removed the sill, and could not find any heat or smoke, leaving the scene at around 6.00 pm. The husband arrived home around 6.30 pm, but could still smell smoke within the house. He could not find the source, so he isolated the power before the whole family went out to dinner, departing around 7.30pm. Around 8.30 pm the owner received a phone call from a neighbour saying that his house was on fire.
The owners returned prior to Fire& Rescue’s arrival and saw a fire in the roof space of the north-west corner of the house. The husband entered the house to retrieve some keys and exited as fire crews arrived.
An initial examination of the scene was conducted by a fire Investigator from Fire & Rescue NSW, starting with conversations with the Station officer from Gordon Fire Station who attended both calls, then the two owners. An external examination was conducted and from the roof collapse it could be seen that the north-east area of the upper first floor. All the Windows on the upper level were broken, but it was unclear if it was from the fire or by mechanical means. Externally, the greatest area of fire damage was on the northern side of the building, at the junction of the upper and lower walls of the first floor.
Here the eaves and timber wall had been destroyed by the fire.
An internal examination was conducted of the ground floor lounge. A fire in the lounge room area appeared to be caused by drop down from the vertical service duct that contained the air conditioning ducting. A room adjacent to the lounge room also showed drop down fire damage via air conditioning ducting. There was minor sooting to the kitchen and dining rooms of the ground floor.
The internal examination continued upstairs, where the main fire damage was located. The lower first floor was a retreat area along the northern wall. Here the ceiling had collapsed the ceiling joists were significantly damaged by the fire, but the walls of the room were not, indicating that the fire was in the roof space. In the master bedroom, also on the lower first floor, the ceiling joists were fire damaged from the top down, again indicating that the fire was in the roof space; however; the ceiling joists were intact in the master bedroom, indicating less fire damage than in the northern side of the lower first floor.
The upper first floor ceiling had collapsed, with fire damage increasing towards the northern end of the house. There were three bedrooms and a bathroom on this upper level, all of which, except for bedrooms 4, showed the fire damage was in the roof space. In bedroom 4 the built-in wardrobe had received significant fire damage with a ‘V’ pattern of burning with its base towards the where the service shaft was located.
This service shaft connected air conditioning ducting to the ground floor. The timber inside this service shaft showed deep charring, with some areas here totally destroyed. The fire travelled through this vertical shaft, but it was difficult to establish if the fire came from below or from above. The owner reported fire dripping from an air conditioning duct in the dining room, so this appeared to be the key area of interest for the investigation.
With the service duct now established as the point where the main fire originated, focus turned to determining the ignition source that started the fire. First area looked at was around where the water pipe that was repaired by the plumber in Bedroom 2. When the plasterboard was removed, burning could be seen to the insulation and timber studs. When the insulation was removed the plastic flashing within the cavity could be seen to have melted to the brick wall. This melted flashing moved to the left of the pipe a short distance and stopped with the plastic undamaged by fire, about 40cm from the pipe. As removal of the plasterboard continued to the right of the water pipe, the plastic flashing could be seen as melted and stuck to the internal cavity brick. Further removal of plasterboard and insulation from bedroom 2 revealed more melted flashing.
The investigation then to the bathroom, where the first fire was reported, with more melted flashing observed below the sill of the window. The bathroom used more plastic flashing around the window and this could be seen as melted a so at the window height. Firefighters saw the charring to the window sill when they removed it, applying water and CO2 to extinguish the fire, but did not see that below the window level there was a fire in the plastic flashing moving very slowly from south to north. The crew used their TIC to identify any other hot spot areas, indicating other hidden fires within the house. The heat and fire in the cavity was shielded by the plasterboard and it is not surprising that the TIC did not detect heat in the cavity.
Removing plasterboard and insulation from bedroom 3 revealed the same melting to the plastic flashing.
Some plasterboard was then removed from bedroom 4 and melting could be seen continuing around the room’s corner and then headed to where the service shaft was. With the plasterboard off the wall, a ‘V’ pattern of soot staining to the interval brick could be seen pointing back to the service shaft .With plastic melting in the service shaft, this is where the fire grew , by igniting the air conditioning ducting which spread into the roof space and then into the wardrode. From this point the fire developed into the roof space, which caused the tiles to collapse in the upper first floor.
The origin for the fire was the copper pipe in bedroom 2, with the source of ignition being the heated copper pipe providing the ignition for the plastic flashing in the cavity. The cause was determined to be accidental.
During the period 2010-2012 there have been 71 fires that have originated in concealed wall spaces. It is difficult to say what you would do in this situation. It is obvious that if the cavity sire was discovered in the original call then the corresponding fire in the roof space would not have occurred. When one is presented with a fire in the cavity that appears to be extinguished and there is no other sign of fire, is it reasonable to start pulling the walls off to confirm extinguishment? What firefighters may have done differently is to investigate the roof space. If a fire is in the cavity, the smoke should travel into the roof space. If this is full of smoke then further investigation of the source of this smoke can be undertaken. As occurred at this incident, a TIC may not reveal the heat in the cavity with the plasterboard and insulation stopping the heat from being detected.
Station Officer Michael Forbes
Fire Investigator ‘A’ Platoon
Fire Investigation and Research Unit
Fire & Rescue NSW