Wind and fire resilience – how we can limit the risk

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By Christopher Mastro
and Frank Lohmann

The Lytton fire, the Barrie tornado and the Calgary hailstorm were chilling reminders that most homes and buildings cannot withstand extreme climate events. This is not a failure of building codes – there is only so far building codes can go. Many effective measures to protect homes, buildings and people during extreme climate events are not related to home construction, but to things such as natural infrastructure upgrades, community emergency planning, and yard maintenance and landscaping. The good news is that for builders, renovators and homeowners interested in investing more to take extra steps against extreme weather events, there are some straightforward and relatively low-cost solutions to help improve the resilience of homes, and the residential construction industry already knows how to do it. The process is simply to a) consider which extreme events are most likely to occur where the home is located, and b) integrate resilience into construction and renovation plans and budgets.

This article focuses on how to improve a home’s capacity to withstand an extreme wind or fire event and to be repairable after the event. We’ll also share some techniques to protect homes during construction or renovation to reduce the business risk for builders and renovators.

 

Christopher Mastro

High-wind resilience

Severe windstorms such as tornadoes create significant lateral (sideways) and uplift forces around a home that have enough power to lift roofs and permanently deform structures. The solutions are not complicated, but a comprehensive approach is required to ensure reinforcing one junction (such as with hurricane clips) doesn’t lead to failure elsewhere (such as the sill-plate/foundation) – this means more fasteners, better sheathing and stronger connections from foundations to walls and from walls to roof framing must be part of the comprehensive specifications. For builders, renovators and homeowners who want to integrate high-wind resilience into their next project, this list of resources will be an excellent starting point:

• The Northern Tornado Project at University of Western Ontario has an interactive dashboard that allows builders, renovators and homeowners to review the strength and location of past tornadoes in their area.

• The CSA Standard S520: High Wind Safety for Low-Rise Residential and Small Buildings may be the most detailed and comprehensive resource in Canada at the moment. It offers best practices for the design and construction of the entire load path of a wood-frame building to reduce potential damage during tornado events as strong as an EF2 tornado. The requirements in the standard are intended to leave homes serviceable or repairable after such an event. Applying the standard partially, say in a renovation, may not achieve the full high-wind resistance, but improving any connection along the lateral and vertical wind-uplift load paths that are accessible during a renovation will improve the resilience of homes during non-tornadic wind events and help reduce the potential damage to neighbouring homes.

• The “Protecting roofs against high winds” blog from Federated Insurance contains many useful tips for maintenance reviews and upgrades to achieve better protection of buildings, which can also help reduce the amount of loose debris from buildings that could damage neighbouring structures. The blog focuses on constructions more typical for commercial buildings – for example featuring flat roofs and giving advice on how to document damage after an event.

• The commercial bulletin from the Institute for Catastrophic Loss Reduction (ICLR) on preventing collapse when a home is under construction is another resource worth highlighting here, because wood-frame buildings under construction do not have the full lateral and uplift resistance and temporary measures are necessary to protect the asset. The bulletin recommends bracing, sheathing wall corners, or simply installing windows earlier to provide lateral strength to the walls.

As noted above, while hurricane clips are often described as a single upgrade that accomplishes everything, it is important to understand that they resolve only one connection in the entire vertical load path towards high-wind resilience. Other connections need to be upgraded at the same time to avoid displacing the damage from the roof being lifted, to the walls being lifted with the roof.

During new construction – and where accessible in a renovation – the most effective ways to integrate hurricane clips are:

• Connecting the truss and the outside of the wall, where the heel of the truss is accessible and the wall below is clad with wood-based sheathing, or

• Connecting the truss to the inside of the top plate and – with an additional metal strap – connecting the wall studs to the top plate.

Alternatively, long structural screws can be used (secured diagonally) to connect both top plates and the truss bottom chord while the exterior wall sheathing connects the top plates to the wall studs.

 

Frank Lohmann

Wildfire resilience

Wildfires behave quite differently than house fires as they move through an area at very high speed and with very intense heat. Homes are most at risk from wind-blown embers landing on the roof or ground and igniting elements of the home. Other risks involve ignitable elements near or on the home getting in contact with flames or igniting at the high radiant heat. Damage is not limited to burning but can also include smoke and water damage to property, as well as lost income if a business must shut down due to evacuation orders. Partially completed structures may be extra vulnerable to damage by a wildfire, as in the case of a high-wind event.

While there is no way to eliminate wildfire risk for neighbourhoods at the wildland urban interface, there are some straightforward solutions to help limit risk in this case as well. Regular yard maintenance and community involvement combined with some design and construction considerations can greatly improve a home’s chances of survival during wildfire, even in extreme circumstances.

• A checklist published by FireSmart Canada can be used as a design tool by builders or as a simple assessment tool before a renovation. It provides advice for the home itself, and for the lot. The home-level guidance focuses on roofing, gutters, vents, cladding, openings such as doors and windows, and attachments such as balconies and decks, while the lot-level guidance focuses on landscaping aspects such as choosing the right trees and plants and placing them in manner that keeps flammable vegetation away from the structure.

• The National guide for wildland-urban-interface fires from the National Research Council is probably the most comprehensive guideline for Canada. Beyond construction and landscaping requirements it also includes a detailed hazard/exposure assessment protocol as well as community-level resources such as emergency planning guidelines.

• The blog from Federated Insurance on a business’ wildfire plan and best safety practices is one of very few resources available focusing on what businesses can do to manage their risk before, during and after a wildfire event. It suggests safe practices before, during and after a fire including a fuel reduction plan for the business location itself, as well as a wildfire plan for the business incorporating training for all employees, for example.

The resources presented here capture some of the simplest solutions to help reduce risk for homeowners and businesses in locations where the level of potential risk warrants increased measures. In some locations, it will also be important to consider integrating wildfire and high-wind measures with other resilience measures for flood protection, hail resistance and protection from overheating. With construction requirements for energy efficiency, carbon emissions reduction and accessibility also competing for housing dollars, the complicated challenge remains to balance the priorities with each client’s budget.
To learn more about risks you may be facing as a home builder, and to find out more helpful ways to protect against perils such as fires and wind, visit
federated.ca.

Federated and Federated Insurance are registered trademarks of Federated Mutual Insurance Company. Used under license.

This content is provided for information only and is not a substitute for professional advice. Federated Insurance makes no representations or warranties regarding the accuracy or completeness of the information and will not be responsible for any loss arising out of reliance on the information.

Christopher Mastro is Director, Risk Services, Federated Insurance.
Frank Lohmann is Director, Building Science, CHBA.