Fire Department Roof Access

Jburgess · January 2012

Here’s some illustrations of the walkway requirements by a local fire department. Sure cuts into roof space and the 3 feet across the top usually has the least shade.
All the dimensions are 3'.

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solar_dave · January 2012

Re: Fire Department Roof Access

Yeah my city has enacted a similar requirement, glad mine went in before this was code.

BB. · January 2012

Re: Fire Department Roof Access

I wounder if an argument can be made that the backside roof provides the ventilation access if it is the same attic space?

On my home (smaller 2 story), it would not have been worth installing GT solar if this was the requirement. A 3kW array + one skylight pretty much fill the roof.

-Bill

Jburgess · January 2012

Re: Fire Department Roof Access

BB. wrote: »

I wounder if an argument can be made that the backside roof provides the ventilation access if it is the same attic space?

-Bill

You can argue, but I have found fire to be less flexible than code review.

It seems strange that the city design review encourages busy rooflines and then fire punishes you for the busy rooflines.

BB. · January 2012

Re: Fire Department Roof Access

Jburgess wrote: »

It seems strange that the city design review encourages busy roof-lines and then fire punishes you for the busy roof-lines.

Amen to that... We had so many requirements for walls/roofs to be broken up and lot line setbacks, everything ended up looking like a weird New England bed and breakfast (without any charm).

Eventually, it got so bad that our city fired the entire planning department and starting over (adding to a second story bedroom would take 2+ years just for planning approval--Made it pretty much not worth the trouble to add on to your home as your kids grew up--they could be out of the house before the project would be finished).

-Bill

firerescue712 · January 2012

Re: Fire Department Roof Access

Here is the reason. Due to the quick, high build up of explosive smoke and gases on a structure fire, fire departments must cut a hole in the roof above the fire at the highest point to allow this explosive mixture to safely vent upwards. If this was not done, and a door or window was opened, a backdraft would occur. Hollywood does a terrible job of what a true backdraft is. Look at YouTube for backdraft videos. Some of them blow the fireplace off the structure, or blow the roof up for a few inches. The reason for the 3' clearance is for safe access for the firefighters to get on the roof. When a ventilation hole is cut in a roof, it must be cut on the downwind side. This is why access must be left on all sides of a roof. If the vent hole was cut on the upwind side, the wind would be funneled down this roof opening and give fresh air to the fire at the highest point. It would either cause a backdraft, or push the fire throughout the structure. Improper or inadequate ventilation can cause unnecessary damages and possible injuries or death to the firefighters. I am not saying the fire departments are right in the restrictions. I am just trying to share the reasoning. The simplest way would be for the fire department to approved the array layout and place a clause on the approval. I would say, it is between you and you insurance company because we cannot safely ventilate your roof. This, the fire will grow until it self vents. Safety above all.

I hope this helps.

niel · January 2012

Re: Fire Department Roof Access

firerescue712 wrote: »

Here is the reason. Due to the quick, high build up of explosive smoke and gases on a structure fire, fire departments must cut a hole in the roof above the fire at the highest point to allow this explosive mixture to safely vent upwards. If this was not done, and a door or window was opened, a backdraft would occur. Hollywood does a terrible job of what a true backdraft is. Look at YouTube for backdraft videos. Some of them blow the fireplace off the structure, or blow the roof up for a few inches. The reason for the 3' clearance is for safe access for the firefighters to get on the roof. When a ventilation hole is cut in a roof, it must be cut on the downwind side. This is why access must be left on all sides of a roof. If the vent hole was cut on the upwind side, the wind would be funneled down this roof opening and give fresh air to the fire at the highest point. It would either cause a backdraft, or push the fire throughout the structure. Improper or inadequate ventilation can cause unnecessary damages and possible injuries or death to the firefighters. I am not saying the fire departments are right in the restrictions. I am just trying to share the reasoning. The simplest way would be for the fire department to approved the array layout and place a clause on the approval. I would say, it is between you and you insurance company because we cannot safely ventilate your roof. This, the fire will grow until it self vents. Safety above all.

I hope this helps.

you know that makes sense to me, but i would have to say that most firemen wouldn't think to determine or take the time to know which way the wind is blowing when they rip into a roof. i have never seen this kind of consideration given at a fire scene and i'm not just talking vfds either as i'm talking paid departments. they pop the roof open at various points only as a means of accessing the fire within and not to just release the gasses.

firerescue712 · January 2012

Re: Fire Department Roof Access

I cannot speak for those that do not calculate the wind direction. They are playing the odds and will eventually lose. I have seen this in person. When ventilated properly, the fire can usually be put out in 5-10 minutes. When done wrong, the structure will slowly burn over an hour or more before it can be brought under control. Professionalism is the key. Regardless or whether career or volunteer.

Another thing i did not mention on the first post, the roof joist/rafters. We are taught to use a ladder laid on the roof to walk from the roof edge (bottom) to the ridge (peak). If a ladder will not reach, we are taught to walk on the rafter, which should be either 18- or 24-inch center. Either way, walking 2 feet from the edge of the roof line going up a roof will place your weight on the rafter. This helps prevent stepping through the roof between the rafters. Like I said, it is all about the firefighters' safety. It is not about inconveniencing the homeowner. I wish fire code people would explain this when they come out.

BB. · January 2012

Re: Fire Department Roof Access

That was what I thought...

Adding some sort of smoke venting as part of new construction would seem to be an interesting option. Most of my roofs are too steep to walk on anyway--And throwing a ladder across solar panels is probably not a great idea either.

But conflicting requirements between fire/planning/building/landscaping/green construction is really a big problem in our area. Would cause the 20% of the homes that may have good sun on a southern roof to be even less capable of adding solar arrays.

-Bill

firerescue712 · January 2012

Re: Fire Department Roof Access

Maybe they could get a homeowner to add a metal ladder between he solar panels on each roof? That would achieve their access and allow the home owner to space the panels closer? It would cost, but might be a win-win situation. Just wondering........

techntrek · January 2012

Re: Fire Department Roof Access

A question, what about gable vents, ridge vents, and eave vents? I have all three. First, I would expect these to be a natural vent system for the hot combustion gases thus making an additional hole unnecessary - after all, they work together during normal hot conditions to vent via convection. So, add them to a house (if it doesn't already have them) when you add a solar system and maybe that covers the problem if the worst happens?

Which brings up the problem of firefighters venting upwind, which you mentioned is a big no-no. A house with the vents I listed above will also allow intrusion of fresh air from upwind through the eave vents, or in a big enough wind through the gable vents. So without an axe or chainsaw being hoisted you are already venting explosive gases and forcefeeding fresh air. Or am I completely wrong?

firerescue712 · January 2012

Re: Fire Department Roof Access

You are correct that the attic ventilation system is already allowing air into the structure. In the event of a fire, the heat from the fire will rise and push the air out of the attic. This is why the smoke rolls out of attic openings. Even with the wind blowing, smoke will push from all vent points from the attic once the heat has risen enough. The firefighter vents over the fire at the highest point to direct the fire through the vent hole and out of the structure. A fire is like water, it travels along the least avenue of resistance. Most ventilation holes are a minimum of 2' x 4' to allow the heated gases and smoke to rapidly vent unobstructed. The vents typically found in attics have restrictions (louvers, screens, partitions). These slow down the movement of the rapidly expanding thermal column of air. It is like water flowing freely in a stream until it encounters a bridge pier. This would slow the smoke down and allow more smoke to build within the structure. When a firefighter properly cuts a vent hole above the fire, it is common to see flames coming out of this hole. It is the unburned gases and carbon particles found inside the fire room. The free flow of these gases acts as a venturi effect and pulls more of the smoke and gases out. It does not clear the structure of gases, but makes it safer for the fire suppression team to enter. It is hard to imagine how quickly the inside atmosphere heats up in a structure fire. It is also hard to demonstrate the pressure the heated gases place on the structure. There are several YouTube videos that show this. But, until you are there, it is difficult to realize. I hope this explains the need to cut a large ventilation hole in the roof. With the advent of positive pressure ventilation fans, many fire departments are hesitant to cut roof vents. This is another issue, though.

waynefromnscanada · January 2012

Re: Fire Department Roof Access

firerescue712 wrote: »

Maybe they could get a homeowner to add a metal ladder between he solar panels on each roof? That would achieve their access and allow the home owner to space the panels closer? It would cost, but might be a win-win situation. Just wondering........

This would be a good idea for many reasons, not just for firefighting. If my roof were covered with PV, I'd love to safely get up there once in a while just to check on things.
And as a former fire fighter, I totally agree with "firerescue712" on all his other writings. And I have a problem with some of the modern building materials, like pre-fab roof trusses, "stapled" together with metal plates which quickly heat, char the wood around the little metal points that poke in the wood, allowing them to fall apart and the roof collapse far quicker than old type construction. Likewise some of the floor joists made up of what amounts to thin chip board mounted on edge, with 2X3's capping it top and bottom, leaving the chip bard exposed. These burn through and collapse in about 5 to 7 minutes, dumping everything and everybody on them, into the fire pit below. Older, real wood 3X10's often took 20 minutes to let go. Not kidding, chills of fear sweep through me every time I see these "modern" floor joists being used.
But I digress.

firerescue712 · January 2012

Re: Fire Department Roof Access

Wayne:

Thank you. And I tip my hat to a brother firefighter. Once a firefighter, always a firefighter. What Wayne said about the modern construction is true. There are videos on YouTube showing a simulated attic fire and how quickly the prefab trusses fail. Even placing a ladder permanently on the roof will not prevent or prolong this. A ladder might actually accelerate it because of the additional weight load. But then, there are already pv panels weighing down the roof structure. I recommend contacting your fire code authority and ask them what you can do to allow more panels on the roof and give them the access required. They should have an open mind to helping all parties in this matter. Placing a smoke ventilation system in a home is rare. You think the fire codes on pv placement is rough, try checking the codes on this. Minimum of 1 hr fire rating, might be 2 hours. Fire rated sheetrock through the complete system. Fire/smoke dampers. Sensors. Battery backups. A dedicated opening for smoke removal. Possible fans to pressure the structure (another dedicated opening). It could lead to a can of worms and be extremely costly. Many things can be expected for this system. Again, it is up to the governing agency how much they require. Has anyone ever thought about extending the panel beyond the bottom roof line? Place the base of the panel mounts on a rigid structure reaching from the ground or tied into the walls? It would be odd looking, but would allow an additional row of panels. That is, if approved. Think outside the box. Think safety and efficiency. Come up with a workable plan, then present it to the fire code people. Just my 2 cents.

bmet · January 2012

Re: Fire Department Roof Access

firerescue712 wrote: »

Maybe they could get a homeowner to add a metal ladder between he solar panels on each roof? That would achieve their access and allow the home owner to space the panels closer? It would cost, but might be a win-win situation. Just wondering........

How to add something like that without also inviting vandalism, or theft, or other problems.

BB. · January 2012

Re: Fire Department Roof Access

When I remodeled my home, I looked into sprinklers...

If I was to install them, I would have to up my water service another couple sizes ($30 a month extra connection fees). And damage wise, it appeared that the reduction in fire/smoke damage was about equally offset by the cost of water damage (fire suppression and leaks).

By the time was all said and done, it was very questionable if the extra costs/complexity/hassles to meet my cities requirements for sprinklering a 80 year old existing home was even worth it... I would have liked to do it (first two store home I have ever owned), but it was just not worth it. Instead, I put sheet rock up and added a fire rated door to the home in the attached garage. Plus added hard wired smoke/fire alarms instead throughout the home.

I am just waiting for spray on fire insulation requirements for "modern" floor/attic joists and other structural elements. Sort of like what is required for metal buildings.

It is interesting that a good wooden home will withstand fire (structurally) better than a metal structure. Wood structure will withstand direct heat much longer than unprotected steel (which loses much of its strength over ~400-450 degrees F--hence the need for fire insulation in a metal structure).

-Bill

techntrek · January 2012

Re: Fire Department Roof Access

firerescue712 wrote: »

...Even with the wind blowing, smoke will push from all vent points from the attic once the heat has risen enough....

...It is hard to imagine how quickly the inside atmosphere heats up in a structure fire...

Thanks for the explanation, exactly what I was looking for. So basically the pressure from the expanding gasses overpowers any wind, forcing a one-way exit from all openings.

The quick buildup of heat is one thing I do understand - and try to get across to friends and family when it comes up. Although I'm not a firefighter, I had a job in a hazardous materials warehouse at one time which required some fire-related training every year. Plus I'm on the evacuation/SIP team at my current job (not my primary job, I just care enough to kick everyone else out the door when the alarm sounds). Training for both jobs included one of those infamous 2-minutes-to-flashover videos (simulated cigarette in a couch cusion). Every time I watch it I get chills up my spine thinking of the people you hear about every year that ducked back inside to get the family dog. Which is probably just about the time that their front hallway hit flashover.... I've told my kids over and over and over, if the fire alarm goes off get your butt outside, by the satelllite dish (our meeting point). Period. If the dog isn't on your lap when the alarm goes off, don't even try to find him or your favorite toy!

Ever since that warehouse job I've carried a keychain flashlight, make a mental note of exits in hotels, bought a half-dozen extinguishers and 5 fire alarms when we bought our current house (alarm in each hallway and each bedroom, extingisher in each car and all over the house) and an escape ladder. Planning on installing a sprinkler system, hopefully sooner than later, which will be challenging since we are on a well. Haven't had a fire drill at home in a while, need to do that soon...

Edit: I started my post before Bill's, just got sidetracked here at work for a while. Glad to see similarities in his post... but Bill, get some fire extinguishers around your house too!

BB. · January 2012

Re: Fire Department Roof Access

Got lots of fire extinguishers (take care of a small apartment building. Refill extinguishers ~$25 each. Buy new extinguishers ~$25 each--Have bunches of "old" extinguishers around our families' home). Probably need to look around and re-stage them--If the family cannot find one in an emergency--then they are not really "available" for use.

The wife does not like extinguishers setting on the piano and coffee table--For some reason she prefers flowers. :roll:

-Bill

Probably does not help that we have a pet rabbit... Very sweet, but he will gnaw through cords given 1/2 a chance.

mike95490 · January 2012

Re: Fire Department Roof Access

BB. wrote: »

..... a pet rabbit... Very sweet, but he will gnaw through cords given 1/2 a chance.

Bump up the voltage on those cords (keep the amps low, like a taser) - should stop the gnawing eventually.

techntrek · January 2012

Re: Fire Department Roof Access

mike90045 wrote: »

Bump up the voltage on those cords (keep the amps low, like a taser) - should stop the gnawing eventually.

And you'll come home to a nice pre-cooked meal.

CDN_VT · January 2012

Re: Fire Department Roof Access

firerescue712 wrote: »

Wayne:

Thank you. And I tip my hat to a brother firefighter. ~~~ There are videos on YouTube showing Just my 2 cents.

Very good information , Please post the videos , that YOU recommend .

Many U-tube are maybe not so true.

It's EZ , once you see one that depicts the area/ video that you're suggesting , please copy the address line from the address bar and paste/post it on here. Linking also might be good, but we will start slow.

& firerescue712

Sign with a name is nice , OK Smokie

VT

Good read & Info Thank you

firerescue712 · January 2012

Re: Fire Department Roof Access

Here are backdraft videos off YouTube....

These videos are not to critique nor belittle the firefighters. They are doing what they always do. Sometimes, the odds catch up to you.

This is the Chicago Fire Department. Watch the smoke out of the attic window when it is broken. The wind seem to be at the firefighter's back. There was apparently no roof ventilation.
http://www.youtube.com/watch?v=ZRdxXSxfmM0

This is another fire department at a fire that seems small, with just smoke showing. Again, no apparent attic ventilation. Watch the chimney on the right side of the screen.
http://www.youtube.com/watch?v=aTQWNCeCBvQ

Another backdraft. Watch how much power the smoke has as it expands outward.
http://www.youtube.com/watch?v=3FJT2QU-xgM

In this video, the use of a roof ladder for safely walking up a roof, and the ventilation cut is shown.
http://www.youtube.com/watch?v=v81PX2Iygkk&feature=results_main&playnext=1&list=PLA7DC3B15DE2A86B8

Watch how rapidly the smoke comes out of the vent hole compared to the soffit area.
http://www.youtube.com/watch?v=Xks-f8tDInQ&feature=related

This shows the need for the 3' clearance at the ridge.
http://www.youtube.com/watch?v=bQXqJwWrbKA&feature=related

Another showing how the smoke egresses out of the vent hole once it is cut.
http://www.youtube.com/watch?v=zugpQPYdMF8&feature=related

In all these videos, look how slowly the smoke is pushing our of the attic prior to the backdraft or ventilation hole being cut. Then, watch how quickly it forces itself out when the backdraft occurs. I hope this shows the dangers firefighters face and why we cut the holes in the roof.

niel · June 2012

Re: Fire Department Roof Access

i'm revisiting this thread as i've got a few points to throw out there concerning the reasoning for arranging the pvs because of fire accessibility to a roof.

it occurs to me that this reasoning may not be sound due to the metal roofing industry as access requirements to a roof would essentially void using metal roofing on the entire roof just as pvs aren't allowed everywhere on the roof. if one argues that they would just go through the roofing then it could also be said and done easier with pvs as one only needs to snip or cut the rails or the posts supporting them to access the standard roofing below and i'm sure in the case of damaging a pv that the home owner would gladly sacrifice a pv or 2 to save the structure below.

also the wires may not always need snipped to do the access and with pv i would have no fear or qualms of snipping the wire even on a 600v (max v allowed) string. it'll spark if the sun is still able to peak through any smoke, but at that point who cares as you just throw away the wire cutters as they've been damaged and power is disconnected quickly. in thinking this over i think the restrictions may be overkill and an unreasonable fear of pv. today's metal roofing offers just as much or more of an obstacle for roof access for fire personnel than pv. even hitting it with a bar that they often use to poke through shingle roofs would essentially give them quick access through pvs. not trying to rip on firemen, but firemen love to break things anyway so why worry about preserving a pv or 2 when the area below it is burning and they pose no more of a hazard or obstruction than windows or metal roofing? to me the electrical hazard is pretty much more in their heads than a reality especially being fully suited up as they are insulated against a shock should that possibility be there and that would only be briefly when one snips the wire.

so what do they do with terra cotta roofs? break into it. pv is no different imho.

Fire Department Roof Access

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