"Tornadoes are violently rotating columns of air that can destroy buildings, flip cars, and create deadly flying debris. They bring intense winds over 200 miles per hour and can happen anytime, anywhere." (FEMA)
Tornadoes are categorized by the Fujita scale, ranking F0 as "Light," and F5 as "Incredible." F4 is "Devastating." Tornadoes typically occur in spring and summer but can occur anytime and in any part of the country.
In an F4 category tornado, "well-constructed houses are destroyed, some structures are lifted from foundations and blown some distance, cars are blown some distance, large debris becomes airborne." Undoubtedly, there is no whole-house protection from extreme tornadoes (F3 - F5), as the speed of the rotating column and the debris it picks and blasts are certainly incredible. Therefore, when it comes to tornados, the only proven resilient strategy is a safe room which we discuss below.
Many states and zones across the U.S experience multiple levels of storms and are forecasted to continue to experience similar or worse weather phenomena. These areas and communities are generally better prepared and build resilience into their homes to withstand storms and keep safe.
However, extreme weather events can surprise both experienced areas and first-time storm-hit areas, stressing the significance of preparing for extreme events.
There are many design considerations, projects, products, and solutions to choose from to properly address storm-related risks. Here are key strategies and best practices to consider when building a new home or improving an existing one to better weather a storm.
This blog covers essentia lstrategies to protect from storms, focusing on tornado risks. Note that this blog does not replace the advice needed by experts to address the specific type of storm you need protection from.
In this blog we will cover:
- Structural load
- Resilient designs
- Design for increased wind
- Safe rooms/shelter
- Flood resistive materials
- Elevated Essential Infrastructure
- Critical system backup
- Power of community
- Final thoughts
Buildings need to withstand both external and internal loads throughout their lifetime. Loads are forces that are imposed on the house’s foundation and frame. The structural load is the sum of all the forces which a house needs to withstand.
There are various types of loads. For example, a “live load” is the force of a moving part inside the house, like occupants. A “dead load” is a force from a non-moving element, such as the roof that weighs on the house.
Wind, snow, water, or earthquakes are examples of external loads on the house. Ideally, homes should be properly designed to withstand a combination of such loads.
We reiterate that although providing strategies to reduce damage from storms in this blog, we advise hiring an expert to properly design your house to help consider all types of loads and not storms only.
Construction engineers, architects, and professional contractors can properly calculate the loads, choose the proper materials and execute appropriately to achieve the desired safety and resilience objectives.
Design for Increased Wind
This strategy aims to reduce the risk of roof tear-off, structural damage, or damage to the primary water-resistive membrane during a wind storm or hurricane.
The designed wind loads of buildings are based on statistical evaluation of past records of wind speeds at meteorological measurement stations. Unfortunately, future trends of wind speeds following climate predictions have not been included in building standards.
Increasing the roof design standard may help protect against the anticipated increase in wind speed or storm severity as it better protects a building from roof tear-off or moisture damage.
Specific measures that impart strong wind resistance to a building include:
- Using hurricane strapping, such as Simpson Strong Tie, or other metal fasteners that provide a continuous load path from foundation to roof.
- Anchoring walls properly to foundations.
- Designing roof geometries that are less prone to wind damage than gable roofs and installing continuous roof underlayment.
- For a gable roof, properly plan the length and width of the gable overhang, strengthen gable ends, and out-looker attachments at gable ends.
- Adequately securing chimneys to the structure.
- Ensure windows and doors meet appropriate design pressures (“impact windows and doors”), in addition to being protected from wind-borne debris. Marvin’s impact-rated coastline collection is one example of impact windows.
- Install hurricane-proof garage doors and tracks, or use a garage door bracing kit to reinforce an existing garage door.
Whether building a new home or retrofitting an existing one, as a minimum, comply with your local building codes. However, if you want to go above and beyond, check out some best practices from the Miami Dade codes. Also, explore the “FORTIFIED” standards from the Insurance Institute for Business & Home Safety (IBHS). It also provides a list of contractors that can help comply with the FORTIFIED standards.
In addition, you can check out the International Codes from ICC, specifically the latest 2018 I-Code sets
Safe Room vs. Storm Shelter:
According to the Federal Emergency Management Agency (FEMA), a safe room is a: “hardened structure specifically designed to meet the FEMA criteria and provide near-absolute protection in extreme weather events, including tornadoes and hurricanes. Near-absolute protection means that based on current knowledge of tornadoes and hurricanes, the occupants of a safe room built following FEMA guidance will have a very high probability of being protected from injury or death.”
To learn more about the criteria for a safe room, check out FEMA P-361: Safe Rooms for Tornadoes and Hurricanes: Guidance for Community and Residential Safe Rooms. In addition, FEMA provides basic information on safe rooms, and construction drawings for site-built safe rooms in FEMA P-320: Taking Shelter from the Storm: Building a Safe Room for Your Home or Small Business.
Note that the criteria have been based on historical data and storm events. As we discuss repetedly, climate resilience is about future-looking events that may become more extreme due to climate change.
The ICC has developed a minimum, specific code for residential and community storm shelters. The ICC 500 was first published in 2008, updated in 2014, and again in 2020. The current ICC 500 2020 applies to the “design, construction, installation, and inspection of both residential and community storm shelters. Residential storm shelters serve occupants of dwelling units and have an occupant capacity not exceeding 16 people.”
ICC further states that “the ANSI-approved standard provides minimum design and construction requirements for storm shelters that provide a safe refuge from storms producing high winds, hurricanes, and tornadoes. It contains design requirements for the main wind-resisting structural system, components, and cladding of these shelters, and provides basic occupant life safety and health requirements including means of egress, lighting, sanitation, ventilation, fire safety, and floor space.”
Flood and Water Resistive Materials:
The concept is to take advantage of building materials that can dry out, resulting in minimal water damage and preventing mold growth. This strategy is especially crucial in locations with a higher risk of flooding.
Examples of flood resistive materials are preservative-treated wood framing, preferably environmentally friendly treatments like borate, fiberglass-faced rather than paper-faced drywall, tile, or resilient flooring rather than carpeting, fiber cement products, and certain types of metals and plastics.
All these choices have eco-friendly options that we encourage exploring. Here are some examples to get inspired by:
- Preservative-treated Wood With Borate-Based Treatments:
Resistant to water, fungal, and insect damage such as termites. Its durability makes it an excellent low-maintenance material with a minimal environmental impact as it reduces the need for frequent forest harvesting. ProWood is an example of a company that provides borate-treated lumber and products.
Though not suitable for all climate zones, Borate-based treatments are a safer alternative to Alkaline Copper Quaternary (ACQ) treated wood. In 2004, the EPA reached an agreement to end the sale of CCA-treated wood for most wood-based products due to its toxic nature. Today, commonly used wood products are often treated with ACQ as an alternative. However, ACQ may have some risks associated with its copper substance.
As always, consult with an expert as different treatments behave differently in various climate zones.
Paper-faced drywalls are more common and affordable, but they pose a risk in wet and humid areas as they can develop mold. Using mold-resistant drywall such as fiberglass-faced drywall may be more expensive upfront, yet it provides longevity and resilience.
- Fiber Cement and Types of Metals and Plastics
While wood is commonly used for sidings, today you can find various types of siding materials such as aluminum, vinyl, stone, brick, stucco, or fiber cement. We consider fiber cement an eco-friendly alternative. However, it absorbs moisture, upfront costs may be high, and requires ongoing treatment after its installation.
Before choosing an alternative for sidings, make sure they are suited for your climate zone.
Avoid carpet and wood in flood-prone zones and opt for more durable, water-resistant materials. Popular solutions under the green category are vinyl, linoleum, cork, and rubber. When looking at both green and resilient options, we advise focusing on linoleum solutions made of 100% natural substances. Vinyl and rubber solutions may use gas-emitting chemicals that impact the environment. It is also necessary to consult with an expert regarding the materials used during the installation process, such as glue, to ensure those are safe and resilient. Check out Duracryl resilient flooring products for inspiration.
In many cases, flood resistive materials are an alternative when more expensive and complex solutions are not feasible. Elevating the whole house above the Base Flood Elevation level (BFE) is the best solution to fullyav oid flood damage if you have the budget and conditions allow. For additional information about flood mitigation solutions, see our Reducing Riverine Flood Risk blog post.
To explore the risk of flood in your area, start with searching FEMA’s Flood Map Service Center or use our tool for the general level of all climate risks in your county.
Backup systems aim to prevent damage to a building’s equipment in the events of a flood or storm surge or provide backup and redundancy for running critical systems.
Elevated Essential Infrastructure:
Elevating infrastructure helps limit the impact of flooding and storm surges on building support systems, including HVAC, fuel supply, electrical systems, and appliances. Elevating essential infrastructure should be to a level above the projected water elevation.
Essential infrastructure systems should be protected from floodwater and storm surges not only to avoid water damage. Moving floodwater and wind surges exert pressure which can damage these systems. In addition, flood water often contains dissolved chemicals, silt, suspended solids, and floating debris which you want to avoid.
FEMA’s P-348 2nd edition from 2017 is a comprehensive guide for professionals that covers principles and practices for the “Design and Construction of Flood Resistant Building Utility Systems”. It is a guide that helps protect all utilities inside a home from flooding. Although long, it’s a great reference to become aware and equip yourself with concepts and knowledge when building or fixing your house.
Critical System Backup:
This strategy helps maintain critical building functions in the event of a power outage or water supply loss. The maintenance and operation of critical systems in the event of a power outage should be prioritized in the design of the building, as well as in operation and maintenance plans.
Critical systems should be backed up with renewable power generation, a generator, or a battery backup system. A building with backup power generation is more resilient than a comparable building without those systems.
Here is information on the differences between generators and batteries.
As for the loss of water supply, many tend to think that it can occur as a result of a damaged pipe and can be fixed relatively quickly. In fact, that water supply can discontinue due to environmental hazards such as droughts, wildfires, storms, snow, earthquakes, and more. Sometimes it can take a while to recover.
Numerous emergency backup water systems can be installed in the house, from basic water storage tanks, such as Texas Metal Tanks, to more sophisticated solutions that rotate the water for you.
Here are a couple of examples:
SPOTLIGHT: The Power of Community:
While governments and societies explore methods to establish forward-looking, climate adaptive city designs and building codes, there is always great value in learning from past events.
Hurricane Katrina taught us that resilience doesn’t begin and end with individual homes, and there is a need for resilient communities. How can communities become more resilient in face of extreme climate events?
The answer is lengthy and involves government entities, organizations, local leaders, and homeowners coming together. However, to simplify it, preparedness in the sense of adaptation versus post-storm recovery starts with awareness and communication.
Here are noteworthy reports about state and local leaders joining forces and going through the tedious, yet mandatory process of long-term planning and execution of building resilience into their residential and business communities:
New Orleans invests in building a resilient future. Their NOLA-Ready website is a great example, resource, and communication tool used to raise awareness, educate, and involve communities. Their 2020 presentations share the types of efforts this community has taken to adapt to climate change and build resilience into their living fabric.
Communities should be informed of a long list of information to help them prepare in advance: climate risks, solutions, local building codes, real-time preparedness strategies, pre-storm supplies and where to get them, evacuation routes, emergency relief centers, emergency numbers, emergency and rescue entities, and their responsibilities, communication plans, locations of shelter, funds for mitigation projects, insurance and rebates, success stories of resilience, and much more.
More information on how to prepare for storms can be found in the following links:
This blog is focused on key strategies to prepare your home to withstand storms. There are additional actions that communities and individuals can and should take to protect themselves before, during, and after a storm.
Storms have a direct impact on our homes, mainly by applying forces on the house frame and elements from high winds and precipitation.
Assuming our house is designed to withstand these forces, we should ensure the materials we use are water-resistant. Flooding can result from a storm and may pose risks to critical systems such as HVAC, power lines, and appliances--all of which should be located above the projected flood level.
Storms create collateral damage such as prolonged power outages and loss of water supply, which can also be mitigated with proper backup solutions.
KEEP COOL. BUILD RESILIENCE. EAMPACT