Dangerous Structures Diaries
Date: June 23rd 2021
Structure: Roof Collapse
1:30 pm Received a call from Head of Building Control about the building.
2:00 pm Arrived at the site and met the Police Officer in charge, alongside colleagues from the fire service. He showed me the building with the collapsed roof and walls. Fortunately, the owners of this building are on holiday and there are no casualties!
Assessing the Risk Environment
It appears that the gable walls have collapsed and the trussed roof has fallen to the side and lodged onto the roof next door!
The trusses are bridging between the adjoining homes with tiles sitting on the trusses.
Without delay I look through the Velux window in the neighboring property. I’m surprised to see all the roof tiles still sitting on the trusses! With this in mind, there is a risk that trusses will collapse allowing tile debris to fall into the rooms below and in the gap between the buildings. This could impact the sidewall of the neighbouring property, together with its roof and windows.
A drone from Hertfordshire Fire & Rescue is used to show the condition of the roof from above. It shows that one gable wall had collapsed into the house. All this load is bearing on the 1st floor.
After my survey, I decided that no one could enter the building as the roof could collapse at any time.
Preparing a Plan of Action
The neighbours could not remain in their property, as I could not determine what could happen to their home if the roof and tiles collapsed. They gathered some belongings, staying on the opposite side of their home, with a view to staying elsewhere. We ensured the gas and water were switched off by the owner as the boiler is located on the wall under the roof.
The area needs securing and a contractor is en route with security fencing. The insurance company’s surveyors will be organising work to remove the debris from the collapsed roof and walls. I informed the parties that we would need to see a risk-assessed method statement for making safe, prepared by a suitably qualified person.
3:30 pm The contractors arrived with heras fencing, installing it to the front and down the side.
Both a fence and heras fencing are restricting access to the gap between the neighbouring buildings. In addition, the site is now closed off, making the area safe. This is a very temporary measure pending the removal of the collapsed roof. The occupants next door needs to move back to their home, so the roof removal needs to happen as soon as possible!
4:00 pm Heras fencing installation complete.
What a day! The rumours that this was a gas explosion are incorrect as no windows or doors were blown out. Accordingly, we don’t know the exact reason for the roof collapse, but it may have had something to do with the original construction. For instance, trussed rafters were originally introduced from North America in the ’60s. Where they’d been used with rigid boarding as a finish under the tiles. In the UK, when used with a simple battened finish, some of these early roofs had problems with distortion and racking sometimes resulting in the gable walls being pushed out of plumb. This led to revisions to British Standards to include better standards of diagonal bracing to resist wind loads.
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Useful links:
Hertfordshire Fire & Rescue Service
