Look for signs of collapse

Some types of buildings under construction or demolition, when subjected to fire, may collapse suddenly with little or no warning. It is important to understand the type of construction involved and the method and sequence of building work being undertaken.

This information should assist in assessing the likelihood of partial or structural collapse. For example, masonry is vulnerable to cracking and bulging, which can lead to sections becoming overloaded. Older buildings may have no mechanical connection between floors, beams and walls so any separation causes collapse.

Any localised collapse or demolition work could either leave slender sections of the structure vulnerable to wind or other load, or could result in the weight of upper parts being redistributed, which in turn can lead to further overload and progressive collapse.

Fire may spread through voids undetected. This may have a direct impact on the stability of the building and be difficult to predict. Buildings may have varying degrees of structural stability even if they are not affected by fire, for example:

• When buildings are incomplete
• During structural alterations
• During demolition
• When there has been neglect and poor maintenance

Further information about signs of collapse can be found in National Operational Guidance:– Partial or structural collapse: Fires in buildings.

Refer to the hazard of ‘Firespread’ in the National Operational Guidance: Fires in buildings