The issue of trusses and fires came up in another thread, and I thought it was worthy of it’s own thread. This issue has a lot of hot buttons (no pun intended) and is very controversial. There aren’t any easy answers.
The first question is generally “Do trusses fail in a fire faster than conventional framing?” The simple answer would be that they probably do – At least in some circumstances. (That’s my opinion anyway) But there are so many different variables, it’s impossible to say “trusses fail 20% faster in a fire” or something like that. This can vary a great deal depending on the pitch and clear span of the trusses, bearing locations, member species and size, construction details, type of fire, where the fire starts, the sizes and species of the conventional framing members you’re comparing them with, etc.
Personally, I think they do fail faster in the majority of cases. But is it fast enough to matter? Are they really “fireman killers”, as has been stated in another thread? Are they dangerous enough that they shouldn’t be used?
I don’t think so, or I wouldn’t be in this business.
First, take a look at the attached chart. It breaks down firefighter deaths from 1980 to 2000. The 6th column shows that 107 firefighters died from “Structural Collapse” during this time period, or about 5 per year.
Since this chart doesn’t specify what exactly collapsed, there’s no way to know if trusses were involved in any given percentage. But since many things collapse during fires, I suspect the percentage is very small. The things that collapsed in these cases could have been trusses, stick framed roofs, floor systems, beams, brick walls, steel bar joists, or total building collapses.
Rather than speculate on the exact percentage that involved trusses, let’s just say that it’s less than 5 per year.
Even if we assume all 5 per year involved trusses, how many of those deaths were caused in part by other things, like human error?
For instance – I recall a story of several firefighters who were killed in Hackensack New Jersey in a large building. (I’m going from memory, and some of the details may be fuzzy) There was a complete breakdown of command and control at the site – The firefighters were running around doing whatever they felt like. One of the fire trucks was even pulled inside the burning building.
When the roof collapsed some of the firefighters were trapped inside but were still alive. They called for help on the radio, but their calls went unanswered since there was no one in control and no one manning the radios. They ended up suffocating before anyone could reach them.
The roof may have collapsed because there were wood trusses in it, but that’s not why the firefighters died. And yet this incident is often pointed to by the fire service as an example of “fireman killer” trusses.
Setting the issue of firemen aside for a minute, what about occupants? Are they in more danger because of the use of trusses? Will the trusses collapse before occupants are able to get out of a building?
While it may seem cold to say so, I doubt anyone could survive in a fire long enough for the roof to collapse on them. They would succumb to smoke and fumes long before the fire progressed far enough for anything to collapse. I don’t know of a single case of anyone getting trapped by falling trusses while trying to escape in a fire. (There may certainly be cases I don’t know about)
So what’s the answer? I don’t have the answer to all situations, but would like to see some changes.
For starters, I don’t think firemen should enter a burning building EXCEPT to rescue trapped occupants. Structures are disposable, firemen aren’t. There’s no sense in charging into a burning building trying to save it, just so the insurance company can total it and have it bulldozed. I realize that every firefighter who dies is one too many. But even if trusses were banned across the whole country, I doubt it would make a significant difference in how many firefighters die each year.
Since roof trusses are used in about 60% of new houses, they aren’t going away. The fire service is going to have to adapt to them somehow – Just as with composite products like I-joists.
I would be happy to talk more about the subject if anyone is interested.
Replies
An interesting subject, and one we've discussed before.
My personal feeling is the engineered beams now being used in floors are probably a more realistic hazard. Simply due to the thin cross-sections, it'd seem like a floor built on these would fail much faster then a floor on top of 2x lumber joists.
Of course, if your numbers are correct, and there are only about 5 firefighter deaths per year, due to structural collapses, perhaps this isn't the place to throw time and money.
It would seem to me that the place to throw time and money is in more firefighter training, better communications equipment. Providing them with the thermal sensing units to help find people in burning buildings, ect.. I forget what they call those, but they're amazing. But, at $25K (?) or so per unit, most fire units don't have them yet.
With any engineered lumber product, you are building with less wood then if solid wood is used. This makes more sense, is more environmentally sensible, ect.. But, it decreases the time a burning building will remain standing in a fire. Whenever you have the same forces being held up by less material, it takes less loss of material to cause failure.
Of course, if you really wish to prevent structural collapses due to fires, the proper response is for us to live in concrete domes, not wood framed houses.<G>
Good topic, be interesting to see what comes up.
"My personal feeling is the engineered beams now being used in floors are probably a more realistic hazard."
I also am concerned about them. I like to see drywall ceilings on them to limit their exposure to fire. But that's not a popular idea.
I suspect that there haven't been as many I-joist floor collapses during fires as there will be in the future. As little as 15 years ago, I-joist floors were pretty rare. But around here roughly 50% of floors are framed with them now.
I wasn't aware they made thermal sensing units that would help find people in burning buildings. Seems like that would be a great tool to have, regardless of the risk of structural collapse. How come we choose from just two people for president and 50 for Miss America?
Didn't our last discussion on this get into the feasability and expense of coating I-beams with fire resistant coatings?
Of course, then wouldn't the joist hangers fail in much the same way as the metal plates on roof trusses do? If the joist hangers, or glue, fail easily due to heat, they you've gained nothing by fire coating them.
Frankly, I was quite surprised at how quickly a joining plate could fail simply due to heat during the last discussion. Quite enlightening.
Perhaps there is a reasonable way to increase the time these joints last in a fire. Banding around the two plates to prevent total seperation. Heavier gauge steel construction of the plates. 1/4-1/2" coating of fire resistant insulation over the joints to gain time. Any or all of these may be kooky, or even (unlikely) practical ideas. All would add cost to the truss. Only extensive engineering and testing would show if any signifigant time gains were made. 5 minutes instead of 3 wouldn't be worth a 30% cost increase, as such a slight gain will likely not matter. 20 minutes vs. 5 minutes may be worth the extra cost.
Do you know of any attempts to modify truss construction techniques to improve fire resistance? If so, what have they done?
"...I was quite surprised at how quickly a joining plate could fail simply due to heat during the last discussion."
There's a lot of difference of opinion on how and why trusses fail in a fire. Some say the plates protect the wood. Others say the plates conduct heat into the wood and burn the wood away from the teeth. Others have said that the plates literally "pop" off the joints when heated. (Although I think this has been disproven)
Keep in mind that all fires are different. Sometimes the fire may hit the trusses at a joint first. Other times the bottom chord or top chord may burn through first. Depends on where the fire starts, etc.
Of course - Somebody along the line has to be willing to pay for all this. I doubt you'll find many consumers interested in forking over money for it.
"Only extensive engineering and testing would show if any signifigant time gains were made. "
And somebody would have to be willing to pay for the tests. I doubt the fire service would, since they see it as an industry problem. And I doubt the truss industry would, since they don't see it as a major concern. I've reached the age where the happy hour is a nap.
Well, as often as I ask for smaller government. . . . .this may be a case where government funding of some research would make sense.
It really seems to be their responsibility. It's certainly not the responsibility of the fire service, though they often make building code recommendations. Government sets the standards or building codes. Truss manufacturers and builders mearly build to meet the code. If there is a problem here, that isn't addressed in current code, then those who write the code have to A) figure out exactly what the problem is (why trusses fail in fires); B) decide if it's a serious problem that should be fixed; C) if it needs fixed do testing to figure out how to fix it; D) rewrite the code to require new 'safer' truss designs.
All of that may happen, but most likely only if several firefighters die in a well publicized fire due to truss failure.
Haven't similar things already occured in specific areas due to excessive structural damage due to earthquakes & hurricanes? The codes have been stiffened to prevent major damage, injury, and death from these specific events (shear walls, hurricane ties, ect). Truss failure is a similar problem.
Still, there are other areas of fire safety that seem, to me, to warrent more attention then this. I think hard-wired smoke alarms are now required in new houses? That is a huge step. Requiring fire egress windows was another good step. I've also long thought that new houses should be required to have a large centrally located fire extiguisher put in the house when constructed ($50-100 cost) plus a smaller one in the kitchen. And, houses of 2 stories or more should have provisions for egress ladders. Perhaps kept in the closet over the door.
But, I've also long thought that new cars should be required to come with a small fire extinguisher. I try to carry one in my cars, but it usually ends up in the trunk as there's no good spot to store it. If a spot was designed in, it'd be more useful, and easier to have one on hand when needed.
The real question, is how many deaths are contributed to by truss failure in fires annually. Likely a very small number. How many deaths are caused by home fires each year? A much bigger number. What would help prevent these deaths?
Bottom line, while interesting, it seems to me that focusing on truss failures, while it may save a few lives, would distract from other areas that need more attention. Area's such as improving fire fighter training, equipment, response times, & communications gear. Area's such as fire extinguishers, ladders, and sprinkler systems in homes.
Frankly, buildings are disposable, and the benifits of trusses seem to greatly outweigh their possible increased fire risks.
I think that one issue that has been overlooked with respect to trusses is the number of injuries and near missess that did not result in fatalities.
Another issue is that the lightweight construction going on today will be with us a long time. Balloon frame construction also presents its unique hazards, but it certainly isn't a common method of building any more. Yet we still have fires in balloon frame buildings.
Part of the concern with trussed construction is that the metal gusset plates (gang nails if you prefer) act as heat collectors and conduct heat into the wood members. It only takes a little char depth for that connector to release, resulting in truss failure. Compare that to the small surface area of a 16d nail driven deep into a 2x.
Boss Hogg is somewhat correct in his statement that firefighters should often reevaluate their tactics if no life is endangered. The problem is, how are we to know if the building is occupied? Are you prepared for the fire department to watch as your house burns to the ground? Probably not - and neither is your insurance company.
There are many emotional aspects of this argument, some of which are valid. In the end, it boils down to what level of risk and loss a community is willing to accept.
For what it's worth, Frank Brannigan KNOWS what he is talking about, even if he comes across as emotional or arrogant at times.
Speaking as a firefighter and a builder . . .
"... metal gusset plates (gang nails if you prefer) act as heat collectors and conduct heat into the wood members."
What exactly truss plates do in a fire is hotly debated. (No pun intended) Some say the plates conduct heat in, others say they protect the wood. I don't think either case has been proven.
There's an article here that has some pictures and discusses it:
http://www.sbcmag.info/past/2001/01jun_jul/plateperformance.htmlYoung man to Dorothy Parker: "I can't bear fools."Dorothy Parker to young man: "Funny, your mother could."
There are a number of organizations that do fire testing on building components and assemblies. Most of these also do testing on other consumer products, which probably takes most of their time and budget. When I first came out of college several decades ago, I went to work as a fire protection engineer (a fairly short lived occupational stint...) and went through training at an insurance consortium laboratory in Hartford, Conn. I can't find a web site on that lab, so I assume it has disappeared. However, the Feds have a fairly extensive fire lab at NIST:
http://www.bfrl.nist.gov/866/frd.htm
There is a pretty good list of fire research organizations at:
http://www.iafss.org/resources.htm
NFPA has an article discussing several fires in which lightweight wood truss roofs collapsed in a fire at (and it does state that the wood trusses at the Hackensack fire were bowstring trusses) :
http://www.nfpa.org/Research/fireinvestigation/articles/roofcollapse/roofcollapse.asp
http://www.nfpa.org/Research/fireinvestigation/alertbulletins/trusscollapse/trusscollapse.asp
NFPA also does various types of research, but I didn't find anything on their site indicating that they had done specific research on wood trusses in a laboratory setting (although I didn't go through all their research reports).
Edited 7/22/2003 9:19:01 PM ET by CaseyR
OK, y'all. A couple or three or four years ago, somebody here posted a picture of a brick chimbly built up around trusses, with the final outcome of truss chords running straight into the side of the chimney. I can't find it, does somebody have a copy of this picture to share?
I like to see drywall ceilings on them to limit their exposure to fire. But that's not a popular idea.
Do you mean in commercial use or do you mean basement ceilings or ??? Would you mind clarifying that a little?
Reason I'm curious is that I've been wondering if straping the bottom of I-joists would tend to make them even more fire-failure prone. Do you think it's better to screw the rock straight to the bottom of the I-joists or is the 3/4 gap created by straping no big deal?
Anyone else got any thoughts/knowledge about this?Any jackass can kick down a barn, but it takes a carpenter to build one.
My thought was that by attaching drywall to the bottom of the I-joists, it would limit the amount of air that could get into the joist space and fuel combustion.
If you used strapping below the joists, there would be a fairly small air space that would allow some air flow. But it would still be better than no ceiling at all, I think.
There have been tests of fire rated assemblies using I-joists. Don't know where to tell you to start looking for them, though.
Actually, I don't see any reason to strap I-joists at all. As I understand it, some guys like to strap joists to help keep them straight, and so they can shim low spots and make the ceiling more level. But I-joists are straight enough I wouldn't think it was necessary. Ever notice how fast Windows runs? Neither did I.
What people are missing is that, when you stick frame a roof you have the ridge the rafter and the ceiling beam, all seperate components.
As I said in the other thread, fires burn in different ways. For instance, If you have a fire in a stick framed roof with 2x8 rafters and ceiling beams 16' on center and just the ceiling beam burns, let's say from the center wall of the house as I have seen plenty of times, the ceiling beam can burn from the center wall and out half way or three quarters of the way towards the outside wall. This does not damage the rafter or top plate. This sometimes happens on just 5 or 6 ceiling beams.
Anyone can still walk on the rafters above the burnt ceiling beams and you just replace the ceiling beam.
If your Trusses 2' or 16" on center which is made out of all 2x4's and the bottom chord is burnt half way or three quarters of the way down like in my example above, what will support the rest of the trusses vertical pieces or angled pieces going to the top chord, NOTHING!
The truss will fail. So if a Fireman or anyone else who walks on that part of the roof is in trouble. It's common sence. How can anyone argue that fact.
Can anyone tell me that if the whole bottom chord or any part of the bottom chord of a truss burns it wont weaken the truss. I don't think so.
I think what everyone is thinking is that the truss burns quicker than stick framing is the the issue, it's not. If a truss is made out of a 2x4 or 2x6, does that mean that the trusses 2x4 or 2x6 will burn quicker then a stick framed roof made out of a 2x4 or 2x6, no.
The bottom line here is that when a truss is burnt all of it's other components will fail and the top chord has to sag.
If you have a 2x4 truss that the top chord/rafter is 20' and the whole bottom of the truss burns, can you walk on that 20' 2x4, NO.
What holds up that top chord, all it's vertical and angled pieces that are connected to it and the bottom chord with metal gussets. Burn the bottom chord out and tell me what all those pieces are connected to and what will hold up the top chord. NOTHING!
If you have a stick framed house with a 2x10 rafter 20' and the ceiling beam below burns, can you still walk on that 2x10 rafter, YES.
It doesn't take much thought to figure out that a Truss is more dangerous when burnt that stick framing.
Is there anyone else out there that does do fire jobs and what are your thoughts on stick framed burn jobs as opposed to truss framed burn jobs?
Joe Carola
After reading through your thread, I'm not sure what your point is.
As you said, each fire is different. I've been to a few fire jobs to measure for replacement trusses. In some, the trusses completely failed. In others, parts of the truss had burned through but the trusses were still up - Supported by interior partitions. Don't approach a goat from the front, a horse from the back, or a fool from any side. [Yiddish proverb]
Makes sense to me. Any jackass can kick down a barn, but it takes a carpenter to build one.
Boss
I can't comment fully, but as I remember from research:
The most structural failure occured at the metal attachments not in
the actual wood.
Trusses were pointed out as they depend on the metal plates for
attaching pieces to each other. Also, since the structure is inter-dependent on each truss for strength, loss of the first truss
or two could cause a catastophic failure. A cascade effect.
Alot of the failures cited were in the older buildings, not trussed,
where the large beams for construction were held together with plates
and such. The structures held together with wood connections faired
much better.
Most research and statistics come from the city and urban environment
and not the rural setting.
Don't know if that helps any.
Jeff
The fire service has a number of documented collapses that were sudden and unexpected, all involving trusses. Many of these occurred in the 80's as trusss construction strated to take off. The building industry has used the firefighter casualty statisitcs to defend the use of trusses saying very few firefighters die because of truss collapse. Firefighters are not dumb and many work part time in the construction industry so the SOP when in doubt is "don't go in the building if you suspect truss construction." In my jurisdiction (county) alone, we average one truss built house a year totaling collapsing within a half hour to a burning heap. Fortunately, smoke detectors, alarm systems, etc. alert the residents to get out, but once no life is threatened, firefighters don't do the interior attack they normally would. Instead, it becomes a "surround and drown" operation. The two most recnt occurrences - one was a basement fire that got hot bery quickly and caused the floor trusses to go - the second was a lighting strike in the roof, the fire moving quickly so that the roof collapsed into the 2nd floor within minutes of fire service arrival (5 minutes from the station). Total fire losses are down due to good warning systems, etc. but when a fire does take hold in a truss built structure, it's usually a total loss. Traditional frame construction has a much better track record.
The Hackensack fire is well documented in a number of fire journals - please read them before making statements about it. Yes there was confusion on the fireground - many times there is as multiple operations are in progress. But the real cause was an unexpected, sudden collapse of the entire structure on firefighters who are trained to do an interior attack. First arriving units found little smoke and began an interior operation with a hose line on what they thought to be a small fire. Unknown to them was that a hot fire was burning in a concealed portion of the truss roof - in this case a steel truss roof - and the steel reached the plastic range and it collapsed.
Francis Branagan has written a number of books and articles about building construction and the hazards they pose for the firegfighter - I suggest you read some of his work and the documentation he provides. And get the July issue of Firehouse magazine - Vincent Dunn from the New York City FD gives detailed hazards in fighting high rise fires that include truss construction (that is very applicable to residential construction).
The fire service has plenty of documentation about the serious hazards of truss construction but the reality is truss construction is here to stay. Instead of builders and firefighters poking fingers at each other, a simple legal requirement of a standard decorative plaque on the front of the house near the house number could warn firefighters of the type of construction (not unlike a hazmat plaque but more decorative). This way, folks can build as they like (as long as they meet the code) and firefighters know the hazard they face in a particular fire.
By way of background, I've had many careers including firefighter and builder. In one of my careers, I was responsible for quality of coated steel products - the same metal used to make the gang fasteners for wooden truss assembly. We were very concerned about the liability issues - we knew the coefficient of expansion for that metal and how easily it can pop-off even in a realtively minor fire, so we stopped taking orders for the end use gang fasteners. Later, I learned to appreciate the beauty of truss construction in post and beam but found that the light weight trusses used in residential construction are there for one reason - to save money. And that's fine as long as everyone understands the downside - and I'm not sure they do.
"...once no life is threatened, firefighters don't do the interior attack they normally would."
That may be SOP, but it's often ignored by firefighters on the scene. I'd like to see it enforced more rigidly.
"The Hackensack fire is well documented in a number of fire journals - please read them before making statements about it. "
I HAVE read about it, which is why I mentioned it. (But it's been a while) The report I read was by Francis Branagan. He's the one who concluded the deaths were primarily caused by lack of "command and control" on the scene. And I'm pretty sure they were wood bowstring trusses, not steel.
"...the reality is truss construction is here to stay. "
That was partly my point. The issue neds to be dealt with. Calling them "fireman killers" solves nothing.
"...light weight trusses used in residential construction are there for one reason - to save money."
I don't buy that - There are other reasons to use trusses. But I don't see that as being central to this discussion.
"...a simple legal requirement of a standard decorative plaque on the front of the house near the house number could warn firefighters of the type of construction..."
I don't see that as being useful at all. If someone's trapped in a house, you're going to try to rescue them regardless as to whether trusses are in a house or not. If there isn't anyone inside, the firefighters shouldn't go in.
I think the NAHB drew up a resolution opposing this, but I can't come up with it offhand.
"Francis Branagan has written a number of books and articles about building construction and the hazards they pose for the firegfighter..."
I've read several things he's written. He seems to use a lot of emotional arguements, and not a lot of facts. I don't have much respect for him. Money will buy a fine dog, but only kindness will make him wag his tail.
You seem to have read a lot about firefighting and in particular, about fires involving trusses. Please share with us some of the places where you read these articles - it makes considerable difference if it was published by the NAHB or by IAFF. These discussions are controverisal because they involve money and peoples lives - and nobody likes to part with the dollars or their life.
Trusses have been used for years - long before they were "discovered" by home builders. Bridges have had truss construction for thousands of years for a basic reason - they deliver high strength relative to the weight of the truss and are easy to construct. And that simply means less money spent - bottom line trusses save money. If they didn't, you wouldn't see their frequent use, particularly in residential construction.
Firefighters are trained to make an interior attack - that based on the traditional construction found predominantly in cities. The heavy timber/masonry construction found in many residential and commercial buildings found in the city (particulalry Eastern cities like New York, Providence, Boston, etc.) allows the firefighter to go into the building and fight the fire. Yes fires can weaken the structure and that's why many fire departments have a safety officer who is constantly monitoring the building - inside and outside and will pull firefighters if there is any hint of structural collapse. What has changed is the residential and light construction over the past 10 years where it is now unknown if trusses are used. Now there is hesitancy to enter a structure if you are unsure of its construction. Thats why firefighters do a lot of pre-fire planning - visiting construction sites before the building/residence is completed to determine the type of construction.
I've been fortunate to work both side of the business - building construction, building materials manufacturer and as a firefighter in both urban and rural settings. Unless you've faced the "red devil" as you attempt to extricate a person or extinguish a fire, you haven't accepted a statement that Francis Branagan makes - that the building is your enemy. The fire is the building's enemy but the building is your's - unless you thoroughly understand how a building is constructed, you won't be a good structural firefighter (and your life is dependent on that). Building folks don't like their "work of art" to be called the firefighter's enemy, so Francis Branagan gets labelled emotional. When my life is at stake, that's emotion enough for me.
You seem to have a lot of energy with this issue - I suggest you join a volunteer fire company in your area. The majority of fire departments are volunteer in the US (and really in most of the world) and they all need help. Your knowledge of building would be immensely helpful and I'm sure you would get a better perspective of what a firefighter faces when they pull up to a "two story dwelling, heavy smoke from side A" - do I pull a line and make an interior attack or do I set up for a "surround and drown"? Are you going to listen to Francis Brannigan or the NAHB - it's your life at stake. Try it.
"Please share with us some of the places where you read these articles - it makes considerable difference if it was published by the NAHB or by IAFF."
Why does it make a difference? Aren't both sides capable of being objective? Or are they automatically wrong if they come from the NAHB or WTCA?
Actually, I've read stuff from both sides. People in the fire service have loaned me books and video tapes. And of course I've seen plenty of stuff from the WTCA and other sources in the truss industry over the years.
"You seem to have a lot of energy with this issue - I suggest you join a volunteer fire company in your area. "
Actually, I've talked about it. But they want people who work in town so they're more available. I work too far away.
I've gotten this suggestion before, and it kind of annoys me. Like I'm not capable of understanding the issues unless I'm a fireman. I don't think that's the case. To me that's like saying you can't understand trusses unless you're a truss designer.If my lips are on fire for you, could I extenguish the flames in your cleavage?
Unfortunately this thread seems more emotional/opinion than searching out facts. Yes it does matter where you read articles - both sides are biased and can/do conduct trials that favor their side. That's why impartial sources such as NIST and FM are now getting more involved - and that's why I asked you for your sources.
"To me that's like saying you can't understand trusses unless you're a truss designer"
I agree with that statement. In one of my many careers, I was responsible statewide for business and industry training which included the constrcution industry. My state - and we are no different than others - offers very little training for the construction industry. Trade unions really pick up the slack but that is mostly industrial work. Resdiential construction is monkey see, monkey do - OJT. Take a rep from a house warp manufacturer or better, a truss designer to a residential site - many times they are appaled at the technique, detail and overall work being done with their product. We found builders don't have the time to train their people, don't want to spend the money or don't care - "I'm a carpenter, are you kidding me? - I know how to lift and install trusses!" Ask who trained them and they'll point to the next guy who points to the next guy. That's fine till you get a liability claim for poor workmanship - and it happens as I found in my work with builders.
My suggestion stands - join the fire service. Distance doesn't matter - you don't have to make that first engine - your help on the fire ground is still needed. And again I ask you as a builder, are you comfortable making an interior attack in a truss floor/roof built home if you pull up with heavy smoke showing? That's what a firefighter faces - do you recommed an interior attack or "surround and drown?"
As the whole reason for this thread, I'd like to add my 2 cents.
First for my background: I'm a professional firefighter with a degree in Fire Protection. I attend numerous continuing education classes every year by some of the most regarded fire service professionals such as Vincent Dunn (FDNY), John Norman (FDNY), Dan Noonan (FRNY ret.) and Jerry Tracey (FDNY). All of these guys are amazing firefighters. I work on a busy (3,000+ runs per year) ladder truck in an urban setting that goes from single family homes to large industrial complexes. Outside of the firehouse, I work in residential construction. I outline my experience only to help qualify my statements.
By referring to trusses as fireman killers, I struck a chord (no pun intented to a truss guy <G>) with Boss Hog, who then told me that I was believing "all the hype they were feeding me". I still don't know who "they" are, but I'm not being fed anything, and there is no hype.
My observations about trusses...
The trusses are held together with gussett plates, spiked peices of metal that hold the members to each other. If this gussett plate dislodges or weakens as the result of fire, the fastening method is gone. I equate this to nails in my 2x10 rafters falling out if there was a fire. Builders and Firefighters alike want the fastening method to remain intact. A 100 foot long steel I-Beam will elongate 9 inches at a temperature of 1000 degrees. This is usually the cause of collapse in older industrial buildings. The beam's elongation will push the walls out. If something as substantial as an I-Beam will expand that much, what happens to that little gusset plate? Since heat rises, those plates are in the middle of it.
A beam, be it steel, wood, or styrofoam -- operates on the premise of compression on it's top edge, tension on its bottom edge, which will find a neutral in the center of the beam. If that neutral is compromised, failure becomes possible. Since a truss is built with chords in compression and tension, the web members create and hold the neutral. If gussett plates for any part of a truss fail, the compressive, tensile, and neutral forces become unequal.
While some people speculate that the smaller materials simply burn through faster causing failure, I am much more concerned about the gussett plates. If there was enough heat to burn the 2x4 or 2x6, what do you think already has already happened to the gussett plates? If they haven't dislodged, we can be sure that heat has weakend the plate.
Trusses also create no compartmentation since there is void space between the webs. Last year, I worked at a fire in a strip mall that that had trussed floor joists. What would have been a rather simple stop ran the entire length of the building through the floor trusses.
From a firefighting standpoint, the most dangerous truss is one we don't know about. Fire will run over your head in a void space until it reaches flashover conditions. This is bad. If you're lucky, when it flashes into the floor below the trusses, you are nowhere near it. Worst case...the fire running overhead weakeans the trusses to failure and collapse occurs. Sadly, most the time the worstcase scenario is what happens.
The chart of firefighter deaths is not a reliable peice of information to look at. Data is always lumped together and is always more subject to interpretation than anything else. I hope the fire service fixes that. However, why are only deaths on this chart shown? What about injuries that were not fatal? Don't those count? And why is a the truss organization publishing this?
Regarding the Hackensack fire, Boss Hog has read a few articles, and he is correct - his recall of the story is fuzzy. While there were indeed some communication problems on the fireground, the guys on the 2nd floor had no reason to beleive that they were in any danger. If that building was marked as a trussed building, they would have been pulling the ceiling down every few feet to see what was running over their head. When they saw fire in the truss loft, they would have pulled out and began exterior operations. If the truss loft was sprinklered, the outcome would also have been very different.
The notion that a fire dept. should pull up to a scene and watch your house burn is nice, but unrealistic. We are legally bound by a duty to act. In my district, we would probably get shot at if we were just watching their home burn! Another reason is for envirormental reasons. The faster we stop a fire, the less harmful products of combustion are released into the atmosphere. Should anybody get hurt in the process? No way.
Some in this thread have written that money to fire depts. should be out toward training, equipemnt, etc. A lot of that depends on the department. For example, New York City Fire has top notch training, great equipment, and some of the best FF's anywhere. But, trusses still fall and guys still get hurt or worse. If you think that your fire dept. needs more money, please call the mayor, town council, or whoever runs your town or city. Very little money to fire depts. come from the federal gov't. It's mostly local and subject to the budget crunch that every town is feeling right now. By voicing your opinion at town meetings for that, you'll probably make a ton of new friends at the firehouse that will buy you a beer and talk about the world with you.
Why does the truss coucil oppose having buildings marked if they employ truss construction? They are fighting to make sure that does not happen anywhere outside of New Jersey. Why?
As I've said numerous times, trusses are a great idea to reach spans that were once impossible. With that, let's mark the buidings and sprinkler the truss loft to protect the members. We know that they compromise faster, why don't we give them some backup?
Edited 7/23/2003 10:56:57 AM ET by anthonydante
I agree with all you are saying except for one small but important point - the fact that you would pull up and let a building burn is not realistic. But what is more important is would you make an interior attack with heavy smoke showing from the 2nd floor if you knew the structure was all truss construction? In the past half hour, I took a break and visited a busy engine and truck company in a major city. I asked the officers of both units this question (no preface to the remarks - just the question): You pull up to a single residence, 30 by 40, 2 story frame construction, about 5 years old with heavy smoke blowing out the second floor windows - what's the first question you ask? And both said "Is it truss construction?" Not " is anyone in there?", not "where's the hydrant?" but what's the construction? They said the answer to that question controls all of their subsequent actions.
The dwelling we puleed up to a few years ago had everybody out - heavy fire in the basement - and one of the members said the house is all truss construction. An all out exterior attack was mounted with a safety officer constantly on watch - within 10 minutes, the entire 2 story house collapsed into a heap. Yes we made an all out effort but we didn't risk the lives of our members with an interior attack. I don't think builders and house owners understand the consequences of truss construction in a heavy fire condition - and unfortunately the fire service overall has done a poor job of communicating that point!
I'm sorry, I may not have elaborated on than one enough. Thanks for catching that.
If we had heavy fire rolling through a house and we knew it was trussed, there is no way we would go in there unless we knew had a viable fire victim.
Working on a truck company, I'm responsible for forcible entry and victim removal in the early stages of a fire. After any rescues have been completed, I may need to go to the roof with another FF and cut a vent hole. If it's a framed roof, I will walk carefully - sounding that roof with every step until I'm ready to cut. With a truss roof, I won't set foot on it. If I can cut a hole from the bucket...great. If not, the fire will need to burn it's own vent hole. As you know, that will increase the fire damages.
If we know that trusses are present as soon as we pull up to a structure, we are much safer already because our tactics will change greatly.
In the job you mentioned, one of your members knew the house was truss construction. Let's thank God he was there! What if he wasn't? Would you have known from the street what was waiting inside? Probably not. The fact that 99% of the time we try to walk through a new residential construction we are declined by the builder doesn't help. It would be such a great training tool for the newer firefighters to walk through a house in different phases of construction, but many people think we're there to write up violations instead of learn. I tell new recruits when the come on that they should look into volunteering with Habitat for Humanity. They will learn more about structures in construction phases, and a needy family will also benefit.
I agree 110% with you and the firefighters you spoke with. Thanks for bringing that point up.
Have a good one,Tony
You previouse post bring to light a code inforcement issue, i.e. draft stopping. the 2002 Kentucky residential Building Code book stipulates in R502.12 that draft stopping must be installed for every 1000 sq. ft. of concealed space that has usable space above/below.
Wood floor truss assemblies are now required to have a minimum of 1/2" d.w. running parallel to the joist.
Your experience with a commercial strip mall seems contrary to my experience in commercial construction, at least in KY and souther IN. The division of large comercial buildings by rated fire wall costruction above and below the ceilings has been rigidily enforced around here for over twenty years. Reinspection by the local fire marshal is a yearly event. Violations are written up, citations issued, fines collected, and follow up inspections are made after the correction periods have passed.
While the use of draft stopping in residential construction is relatively new, it is being included in most all of the new codes. Residential inspectors and permitting agency need to enforce those sections of the code.
It may not solve all of the problems of truss failures in a fire, but it certinly would slow down the rapid advance of a fire racing through an open web floor truss and trapping firefighters working under or over them.
What are the code requirements in your area?
Dave
Tony - thanks for the validation. I was an auxillary in a major city department on a truck company (100 ft. tiller) during the roaring 60's and 70's - many 8, 10 ,12 alarm fully involved block square commercial structures - saw lots of action. Now living in a rural part of the metro area, runs are more brush fires, chimney fires and the occassional dwelling and about once a year a good worker at a commercial structure.
You originally raised a point I also raised to BossHog - a placard of some kind - not unlike a hazmat placard yet more decorative - could be placed on side A of the structure. Remember the old fire placques from the early volunteer days - 200 years ago - quite decorative (and now worth some money). I think we need to do more education to both the general public and the building community - trusses are here to stay but let's make them be a safer option than they currently are.
Good to chat with you!
Ed
I jealous, brother! I keep telling the Chief we want a tiller! We're in a 100' Sutphen bucket, which is a nice truck, but tillers are the cat's pajamas! We tell the chief it's for tactical reasons, but he knows better! Not to mention the price tag. Close to a million bucks for one peice. We better start selling X-Mas trees like back in my volunteer days to afford it!
Stay safe,Tony
Something other than placards might be more useful. Many local government agencies are implementing digital geographic information systems (GIS) and many public safety departments are installing mobile data computers in their vehicles.
So here's something to think about: create a GIS map layer that shows by address whether the building on that parcel has truss or stick-built construction. Then install computers in the fire vehicles that have links to the GIS. Those responding to a fire would know through info from their onboard computer whether the building had trusses or not. And they'd know it before arriving at the scene.
While I LOVE the idea, most small departments can't afford to buy gear for all of their members, let alone implement technology that. Someday...maybe.
A big problem with such technology is that it usually requires somebody to administer it. Much of America is comprised of volunteer depts. that cannot afford to hire somebody for this cause.
You are 100% right, that would be an awesome way to do it, but I think the placard is the most reasonable and easiest to implement option.
I see what you're saying. The Fire Department I'm familiar with is in a small, wealthy, and very progressive city. All professional firefighters with all the bells and whistles you could imagine. Gives me a kinda skewed perspective.
Excellent point Dave! Many of the larger fire departments are going with GPS and many pieces of fire apparatus already have data terminals. There is a big push to use data systems - it's even more critical in industrial locations where there are hazardous materials - knowing what is stored in a warehouse is critical to how you approach a fire situation.
The ideal scenario is a fire call is received and processed through an "enhanced" 911 center and the approcpriate stations are dispatched with printouts listing everything from hydrant locations, best means of access, unusual/hazardous items, persons needing assistence who may be in the structure, etc. Some departments are almost there with this detail but many are still working on funding to complete the tasks. My county is still trying to get the contractor to finish the GPS work. And there are now communications problems with cell phone chanels interfering with the trunked systems many emergency services are implementing. Motorola claims to have a fix but there is still concern about communications.
The bottom line is there is a way to work with the building industry but both parties must come to the table willing to work with each other - I'm not sure everyone is ready for that.
Instead of just printed lists, how about floor plans? Most now are created as CAD files, and could be excerpted down to the info you need and stored on a server. GPS coordinates could be used to link to the floor plans of the structures. Wireless download to the fire truck and print out while you're on the way to the fire....
-- J.S.
You are correct John, but the technology is still slow in coming. Emergency services are still struggling with reliable voice communication systems. They started in the 39 and 46 mz range, went to the 150 with repeaters, then the 460 and now 800 mz, the same technology used by cell phones. With all the improvement, there are still serious dead spots - New York has a terrible time. But I suspect there will be solutions and what you suggest could become more feasible in the next few years.
Yes, part of the hold-up is the transition from our old analog NTSC television system to the new digital one. TV stations will simulcast on two channels until we get enough of the new sets out there to turn off the old transmitters and re-claim the spectrum. Some of it is getting sold at auction, and some is earmarked for emergency services.
-- J.S.
I have read the thread with interest, and noted Boss Hog made the following comment of Frank Brannigan: "I've read several things he's written. He seems to use a lot of emotional arguements, and not a lot of facts. I don't have much respect for him."
I thought that it might be good to have Mr. Brannigan's input. He sent the following, and asked that I post the following.
Now I am not in the truss business and have no interest in that business and from reading this thread think that there "might" be some issues that need to addressed about then in terms of fire safety.
But after reading that letter from Frank Brannigan I agree with Boss Hog.
"I explained that in a fire, firefighters would get on top of this burning pile of kindling to cut a hole in the roof to let the smoke out so other firefighters could get into the building. Collectively the audience gasped."
A discussion of the problem does not need to depend on theaterics.
No matter what the issue is when I see this kind of writing I am immediately turned off.
Let makes emotional arguments on the other side.
He claims that truss are just used to cut cost and increase profits.
He is right.
Thousands of people jobs depend on truss. He was TO THROW THOUSANDS OF PEOPLE OUT OF JOB!
Without truss the price of "affordable houses" will increas AND TEN'S OF THOUUSANDS OF PERSONS WILL BE HOMELSS!
Does he want to be responsible for A HOMELESS INFANT FOUND FROZEN TO DEATH IN THE ARMS OF HER DEAD FROZEN MOTHER!
THAT IS WHAT HE WANTS TO DO.
Now that is the emotional arguement for using trusses.
He wrote a hell of a long letter for not having time to get into a chat room.....................(-:
I want to make a couple of comments on things that he said:
"Particularly, I think your advice about pulling out of building when the structure becomes involved in fire is sound advice."
That's what I said earlier also. Once the structure is fully involved, there's virtually no chance anyone is alive inside anyway. Time to get out of there and do the "surround and drown".
"In years gone by the fiberboard industry threatened legal action to suppress the hazard of combustible acoustical tile. The opposition folded after the terrible disaster at St Anthony’s hospital and a very substantial judgment against the supplier of the combustible acoustical tile.
He's brought up this same scenario over and over for some 20 years - It makes a nice emotional arguement. A fire in a hospital killed a bunch of nurses and babies. Had nothing to do with trusses, but he uses it anyway. This is one of the reasons I say I have no respect for him.
"A most dangerous situation exists when trusses are extended to be the support of the only exit from a garden apartment..."
Seems to me that there should be more than one method of egress here. This has less to do with trusses than with building codes and code enforcement.
Doesn't seem to me that he has presented any useful info here.
If you wanna get Brannigan in here one of these days, I can invite someone from the WTCA (Wood Truss Council of America) and we can let 'em slug it out. The wise man would rather see men needing him than thanking him
Boss,
well thought out issue with one exception,
what is the solution?..
I tend to agree with your conclusions, yet the correct solution would be to go back to timber framing where the house will stand for hours while fires rage (especially if built to the european standards where an insolated metal connection is required, Lag bolt or steel pin covered with a wooden peg)
that simply cannot happen..
there are darn few timberframes built.. Less than 2% of homes are log or timber built due to costs involved..
If 5 firefighters are killed on an annual basis that while tragic is too small to make any massive or expensive change in currant construction methods in the 1.6 million new homes that we will construct this year.
frame with steel and the risks would be greater.. look at the world trade center.
I suppose that we could use concrete or some such material to construct, but that would entail another whole set of problems. none of which are solved as yet..