Post-Fire Risks

Notre Dame Cathedral Restorers Share The Same Concerns

Fires can be devastating to the properties, neighborhoods and families that they affect. When we see, read or hear of reports of fires we wonder how it happened, who it impacted and hope no one was injured. But as the news reports come and go and the next fire is reported on, there is much work to be done on a fire affected property to return it to its pre-loss condition. Assessing and addressing the damages in a timely manner is key to mitigating the loss.

Fires cause damage to a structure in three ways:

  1. Direct fire damage to the structural members and interior surfaces (e.g. charred wood, deformed steel, spalled concrete due to flame and heat of the fire)
  2. Smoke and soot infiltration throughout the building and onto the surfaces and into the cavities of the building
  3. Fire-fighting suppression water that damages interior finishes, promotes secondary damage in the form of mould and damage to materials through rapid temperature changes

Obviously, the direct fire damage i.e. a burned-out roof can leave a building susceptible to exposure to the elements (i.e. snow and rain) which can exacerbate the environmental effects in the form of mould growth on building materials and surface finishes. Therefore, it is critical that temporary protection be implemented as quick as possible to try to mitigate the secondary damage, especially if the remaining structure is being salvaged. This is the situation that is currently being confronted in the fire that damaged Notre Dame Cathedral in Paris. Ideally, the fire-damaged elements can be removed, and new temporary roof platform constructed that can be protected and sealed, rather than simply putting tarps over the fire-damaged structure where it can deteriorate and be punctured. Further, temporary protective measures can buy time especially if the structural repairs are complicated, i.e. a townhouse complex truss roof with a triangular footprint or an 850-year old wooden roof structure.

As a fire burns, combustion by-products such as smoke, soot and other chemicals can be deposited throughout the building on exposed surfaces and in hidden areas, such as wall cavities. Smoke and soot can be distributed via the fire’s energy and temperature extremes causing pressurization differences with respect to adjacent unaffected areas and through a building’s heating, ventilation, air conditioning and refrigeration (HVACR) system. Areas within the fire impacted building may appear unaffected by the fire because there is no obvious structural damage, but deposited combustion by-products can leave particulate, smoke odours and residual chemicals that that can be an ongoing annoyance or can lead to chemical exposures resulting in negative health effects to the building occupants and workers. Additionally, unaddressed combustion by-product impacts may cause corrosion and eventually lead to failures of electrical and other building systems within a property. A complete smoke and soot assessment can be the key to properly allocating resources and flagging items for removal and cleaning.

Fire suppression water and secondary water damage from the property being open and exposed to the elements, also has negative environmental impacts in the form of mould growth on building materials. Wet areas should be noted, and steps should be taken to dry these areas within 24 to 48 hours to help prevent mould growth. Where mould growth cannot be prevented, a thorough mould and moisture assessment will identify the extent of the mould impacted building materials, so these areas can be remediated in accordance with the applicable legislation and guidelines.

As forensic engineers, we often provide advice on difficult decisions related to the protection of a fire-impacted structure.  Our preference is generally to take a more robust approach (as shown in Photo 1) to protect the interior of a structure, rather than a simpler and lower-cost approach (as shown in Photo 2) which is intended for short-term protection.  Often trade-offs are made in the name of management of a loss that can downplay some of these longer-term future risks.  Our advice to industry practitioners is to consider the risks over the life-cycle of a loss event and the intended time and extent of the remediation phase.  It is often perfectly fine to take a simple and low-cost approach, but in cases where the interior is critical – such as at Notre Dame Cathedral in Paris – or a long reconstruction period is expected, it may be wise to consider (with greater weight) the need for more robust protection of a damaged property.