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Fireground Command Considerations - Operating At (or) Underneath Excessively Snow Loaded Roofs
With the recent multiple snowstorm incidents in the Northeast, the fire service needs to take a look up before we commit to an interior or exterior operation. The type of structural material, design and condition all play a big part on whether that snow load is going to be a problem.
Yesterday I took a few minutes to travel around my response district and took an assessment of any potential hazards to my company. I was surprised to find that more than ¾ of the dwellings in my district were still heavily loaded with snow.
In this photo: Older Farmhouse with a noted sagging porch roof
When we arrive at a dwelling for a reported building fire, the snow load should be directly considered when the incident commander determines a strategic plan. Potential roof collapse before the fire started should be a consideration as well. Considering that the structural support system may be directly or indirectly under attack by “the fire” can add to the potential early onset building collapse. Another consideration should be on the newer dwellings that are constructed with the lightweight “truss-roof” system. As seen in many past fire tests, a lightweight truss roof system once assaulted by fire fails at an alarming rate. None of those fire tests were conducted with a snow load as seen by our companies this week.
Farmers porch buildup that hinders normal 8/12 pitch roof snow slide
Heat loss from a building may result in some snow loss through melting between storm events. Roofs that allow heat loss to melt snow are called "warm" roofs. This may be by design or lack of proper insulation. Other roof systems remove lost heat before it has a chance to melt the snow. These roofs that prevent heat from reaching the snow are known as "cold" roofs. Sometimes buildings are either unheated during winter months or are intentionally kept at or below freezing so there is no heat loss that results in snow melt or ice build-up.
This photo example displays both a Warm Roof (on top) and Cold Roof (porch)
One factor that needs to be considered by incident command is how does the FD safely commit to an interior firefight while considering the level of danger? What are the dangers to be considered? Well it is not as easy as what you see from the street. Understanding building construction has never been more important when you add-in snow loads. Do you expect normal tasks like fire suppression and search/rescue to be done quickly when firefighters encounter delayed ventilation? Interior companies will certainly encounter an under-ventilated fire condition. Interior conditions will not be the same as operating during the spring, summer or fall months. Ladder companies will certainly have a delay in providing vertical ventilation due to lack of access to the roof, snow banks that limit truck access, carrying a ground ladder in deep snow is difficult at best, and access to the physical roof may be buried 18-36 inches below the snow. Adding firefighters to a potentially overloaded roof can trigger collapse as well. Not too often do we ask the truck company to bring a snow shovel with them to just find the roof’s surface. Attempting to stay on the aerial to get the job done safely? Well good luck trying to shovel from there. These delays will definitely change the interior company’s exposure to extreme heat build up and unique fire dynamics.
Lightweight Construction – Very Large Farmers Porches are great snow load collectors
Every firefighter on the fire ground from the Fire Chief right down to the newest firefighter needs to stay alert to signs of overhead hazards during the winter month operations. There has been a lot of focus on building collapse lately but staying cognizant to potential heavy snow or ice slides can cause serious personal injury or death to responders. This type of overhead assessment must be done on arrival and continued to be monitored as the incident is mitigated.
For you incident commanders, this is an excellent point to add to your exterior safety officer’s checklist. We need to also stay alert for any signs of a building weakened by the fire or pre-fire snow loading, listening for strange noises of the building settling under the unusual load, noting any visual signs of sagging roof eaves or leaning / bowing / separating wall connections, interior wall board cracking or noting water seeping from above are all positive indicators of a potential collapse is pending.
If you choose to go interior and aggressively mitigate from underneath, I highly recommend using my expanded command team approach to managing an incident and assigning an Interior Safety Officer to assess these specific hazards. As we all know, our initial interior companies are many times taxed beyond their control and may miss some of these potentially lifesaving signs of danger ahead.
Bottom line is the fire service should use a strong risk verse gain decision making model, and chose the appropriate model to get the job done as safely as we can.
Take care and stay safe.
FETC Services
Average Training Breeds An Average Fire Department, Let FETC Help You Achieve Excellence!
Replies to This Discussion
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Permalink Reply by Jack/dt on
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FETC,
Maybe you should have asked what color a roof should be; a lot of people seem have very strong color preferences in here.
As to your post: Another thing to consider besides roof load and collapse potential is, should there be a fire(or heat) in the attic, that section of the roof being heated has the potential to cause the snow load to slip. Heat melting the snow will cause water to run down the roof, beneath the snow load (a key sign is water running off at the eave), essentially *greasing* the roof. It is not inconceivable that a large section of the roof snow load can slough off, bringing down enough snow to bury someone unlucky enough to be standing down below. Not to mention that if you're on that section of the roof it's taking you down with it and any ladder at the eave.
Also on buildings that have significant heat loss at the eave (wall/ceiling intersect) considerable ice dams can accumulate (I've seen ice dams as thick as 10+ inches at the eave). Stepping off of the ladder onto this ice can send one right off the roof. Likewise, with very little heat from beneath, the ice damn can release, dropping huge chunks of ice which can cause significant injury to anyone beneath.
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Permalink Reply by William Allan Milfred Harper on
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After reading this comment on snow and roofs, is there no way that the prison system could take these
inmates and have them clean off the roofs . The prisoners could use long poles , to get most of the roof
clear of snow . This is just an idea , but we are paying for their up keep , so this would give back to the
community . I would also recommend that a safety inspector go with the guards .
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I don't believe this issue was HOW to clear roofs but to increase awareness and knowledge while working on, below or near.
A discussion on how to clear a roof only threadjacks FETC's discussion.
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Permalink Reply by joemac on
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This falls under the heading of Situational Awareness.
I hate dealing with the hazards of firefighting in the snow.
Besides the dangers of snow load and roof ice, there are those obstacles that are well-hidden under a heavy blanket of snow that would normally be seen, such as garden equipment and children's toys.
Size up definitely changes when there is a ton of extra weight up there, along with the inherent slip/fall hazards.
Be extra careful out there.
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Permalink Reply by FETC on
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Jack-DT third to last paragraph:
Every firefighter on the fire ground from the Fire Chief right down to the newest firefighter needs to stay alert to signs of overhead hazards during the winter month operations. There has been a lot of focus on building collapse lately but staying cognizant to potential heavy snow or ice slides can cause serious personal injury or death to responders. This type of overhead assessment must be done on arrival and continued to be monitored as the incident is mitigated.
We had a guy nearby the other day pulling a roof rake, bury himself for hours until someone heard faint cries from the snow pile. Good observation and point to reiterate. Thanks
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FETC, A huge area of snow (or ice) sliding off isn't something that many will automatically think of, so I spelled it out a bit more.
Another thing that occurred to me is the use of Roof Heat Tape. It's 120 volts and, while recommended that it be plugged into a GFIC outlet, they typically aren't. It's further recommended that they be replaced every 3 years to avoid cracking/drying, which increases the risk of electric shock.
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Permalink Reply by James Hawk on
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we had the same thing happen in a nearby town here.
also weve had several barns collapse in neighboring towns.
roof ventilation this time of year can be very dangerous as snow and ice can unexpectantly break loose and fall off of the roof, carring anything and anyone on the roof with it.
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