fire damage in lvl framed buildings
barrmo4321
| Posted in Construction Techniques on
Everyone likes the big open spaces the new engineered lumber allows us to create, however I hear fire-fighters dont like the glued up joists bacause they fail more quickley in a fire. Is this true? anyone witness the aftermath of one of these newer structures post-disaster? Barmo
Replies
Barromo 4321
I've seen a house fire where the lvl failed at a point where the plywood above it was barely burning thru.. the house was only under construction, not sold and everybody quickly replaced things and kept shut about it for fear it would affect future sales..
Simple repair and it didn't even take the crew a half a day to effect.. without the usual carpet etc.. to stink the fire smell was barely noticeable and as quickly as it was closed in they went and sprayed shellac all over everything to trap whatever smell remained (I couldn't smell anything a week later.. even before they sprayed the shellac)
The LVL didn't look that badly burned however it did look shattered..
There are a lot of potential fire issues with many of the new materials we use to build homes. It's difficult for codes to keep up with advancements and the desires of home owners to continually push past old designs.
For example, using big LVLs to open up a space may reduce the redundancy in a structure so that there is less material acting to support a roof or a wall. Then when things start to fail because of a house fire they fail much more quickly and catastrophically.
I know some of the glues involved in manking engineered beams are good fuel for fires too, but I assume that they are treated to provide the appropriate fire resistance.
You also run into issues with high performance concrete in a fire too. Unless it's properly treated and cured you can get instances of explosive spalling. Imagine pieces of concrete popping out like bullets from wall faces and columns during a fire while you're inside it trying to put out the structure fire.
It'd be interesting to hear from a fire fighter who had experience on this.
Best regards,
Chris
Chris
That's one of the reasons I used timberframing.. an hour after the fire starts you can causally wander into my place and not worry that something will fall down or collaspe..
those big timbers take forever to burn thru and I took the thing to a whole 'nuther level of protection when I built according to European fire codes.. Traditional timberframes can fail when the pegs (trenails) burn thru.
European fire codes require a metal connection covered with wood.. the wood insulates the metal from the heat conduction thus allowing the joint to remain solid long after a traditonal timberframe will collaspe..
In addition instead of spreading out the load to use as few timbers as possible I went the opposite direction, I have a bent (frame) every 4 feet where 10 or 12 feet is more normal..
In my bedroom they are 2 feet on center..
MY joists are hardwood which is slower to burn thru than even tradional stick framing and since they are thicker as well with far closer spacing than any code calls for the level of redundancy is astromical.
For example I have 2 inch thick (not inch and a half they way demensional wood is) by 12 inch tall hardwod timber joists 12 inches on center or less and they only need to span 9 1/2 feet..
my subfloor is two inches thick hardwood with another full inch of finished floor above that.
most connections are not nailed but screwed with stainelss steel hardened 18/8 laga screws as large as 1/2 by 12 or larger
A home built according to code requires 208 foot pounds to tear the rafter off the top plate,, mine would take well in excess of 15,000 pounds!
The insulation is SIP's which if you are familar with them are extremely fire resistant. Unlike other forms of insulation which actaully assist combustion.
Frenchy, I love the way you build. Unfortunately, there is not enough hardwood, or softwood for that matter in the world to sustain quality of this type.
Just within my lifetime, not to mention the period before 1950, the entire globe has deteriorated SIGNIFICANTLY.
We are creating plastic sand dunes in Hawaii (billions of creatures are dying annually by feeding on plastic, which was found floating on the surface of the ocean, to their young - and the ocean has 40 times more plastic than plankton available as an ostensible food choice for birds, fish, and whatever), burning through the remaining oil deposits (let's go ahead and add the wildlife arctic refuge to the list - it won't matter anyway!), slashing rain forests, and encouraging people to "abstain" from sex (pie-in-the-sky, if ever there was one), trashing lessons learned and so on...
Try to encourage the reduced use of plastic, except as a recycled product. In the century of tobacco, plastic may prove to have even a more devastating legacy. Don't buy anybody's bottled water. Make your local water sources step up to recognized standards instead.
Your great grandchildren will thank you.
Sasquatch,
Well a couple of points. I use local products.. If I lived in the arid southwest I'd built with adobe, If I lived in Florida I'd build with ICF's * In Hawaii what ever is overlooked, maybe with all that plastic you are mentioning.. ;-) Further by building something well you give it life far beyond the norm.. In America the average age of a home before it's torn down or extensively remodeled to the point where a new home is within reach is 56 years.. Timberframes in Europe because of their strength and durability last for many a century. There are pictures of timberframed homes in Europe that survived bombing and shelling as the various armies fought WW1&2 Drive there today and they still stand! Still are lived in.
Sustainability has to do with the durability of what you are making outlasting the length of time it takes to grow the materials to do so.. Only a handful of my timbers are over 200 years old so based on the European experience there is a very real possibility that trees planted when mine were harvested will grow and be harvested several times before my place succumbs to the affects of aging..
While Foam is a form of plastic It's greenness offsets it's potential for pollution.. we cannot ever take simplistic views that something is all good or all bad.. The use of foam dramatically decreases the need for energy to heat my home.. I don't care if that energy comes from oil gas or electricity the less I use of it the better off the planet will be..
What is bad about plastic is the way it's discarded.. recycle it and we have a different story.. In the right place in the right environment some things that are bad can have some real benefits..
Edited 11/8/2007 8:08 pm ET by frenchy
Edited 11/8/2007 8:11 pm ET by frenchy
You are right that firefighters don't care much for these new building designs. It started with trusses and has expanded with time.
My own house has a 1st floor framed with TGI's 12" X 16" centers. I had the Asst Fire Chief working on the burner and he said knowing that there was a 1.5 inch pour of gypcrete plus tile over the joists no way was he sending a crew into the basement and possibly not the building if there was a cellar fire. I replied that as a firefighter, I didn't want any crew in the house and said to let it burn. We'll put the second one up in less time.
Just save my concrete.
It's kind of hard to answer a question as broad as the one you ask.
First, you have to distinguish between improper use of materials, proper use, and rated assemblies.
Use materials in the wrong way, and all bets are off. With anecdotal stories, we have no way of knowing if it was the material at fault - or the design.
Likewise, terminology is important. An LVL is not a Glulam is not a laminated beam .... etc.
A rated design is just that - a design that has been tested, and meets the requirements. A 1-hr ceiling will perform pretty much the same in a fire, whether is is made of masonry, steel, or wood. That is to say .... it will likely fail so after that hour passes. The manner of failure may differ slightly, but that's only of interest to the designers.
<<It's kind of hard to answer a question as broad as the one you ask.First, you have to distinguish between improper use of materials, proper use, and rated assemblies. . . .>>Your answer is right on the money.I worked as a firefighter some years back, was training to be a line officer, and stopped a few credits away from a degree in fire protection engineering.There are more considerations than can be usefully addressd in a broad manner, the best reply I could ever give is to build according to the rules and do a good job.In my experience the quality of the finishes (how well was the drywall installed, how sloppy are the penetrations) and the contents of the building are far more important than the structure itself when the fire is of equal or less duration or intensity than the rating of the structure.Once you've exceeded the time/temp of the rating, it's a particularized judgement call.I agree with everything Joe Carola said.Something I've always wondered about and never really investigated enough to form a worthwhile opinion is how the behaviour of the truss plates affect the overall performance of the truss in a fire. Steel is pretty much useless from a structural perspective at 900 degrees. It wouldn't take those thin little truss plates long to hit that temperature, and I wonder what that really does.As for the burning part, yes, trusses, I-joists, all those thin sections are scary.The heavier sections, like engineered beams, I think you addressed.
Are you talking about I-joists?
I had heard firefighter's concern about lvl joists. I wonder if glulams or truss joists fail similarly. Seems to me it wouldnt take much burning to make the chip ply web of an I beam fail. Obviously rocking with 5/8 makes a big difference. But most folks around here like to puncture the rock with lots of 6" holes for recessed lights etc. Just wondering what folks have seen as we experience the full range of possibilities of our new wonderful materials. As reports are written about the disaster in San Diego area maybe we will learn more. Barmo
I had heard firefighter's concern about lvl joists.
I've only used lvl's for floor joists a couple times and only a couple times for rafters. It's very rare that you will see a whole floor out of lvl's where I am from.
We use lvl's every day for girders, doubling up stairwell openings, fireplace openings when using I-joists. We use them for supporting loads above the floor, headers.....etc.
I've been doing fire jobs for 17 years now and I-joists and floor trusses are the ones that I've seen burn the worst. I-joists have a 1/2 piece of plywood. They are toasted. Floor trusses are wide opened and forget about it.
2x floor joists burn, but not as bad. The fire has to burn through 1-1/2" of material compared to a I-joist which is 1/2" and a floor truss, well, open shaft.
Joe Carola
Does anyone know what percentage of homes in the US have serious house fire every year?
I agree that I joists and trusses are not as desirable as 2x material when a fire hits. But I can't help but wonder if we're designing homes to meet a standard that is more than likely never going to happen?
Jon Blakemore
RappahannockINC.com Fredericksburg, VA
I don't know the percentage.And I really hope you aren't suggesting we build to a lower standard.The codes we have in place are a minimum for life safety. A bare minimum. I will tell you from personal experience that being inside a fire is not unlike a small hell on earth for the folks who are on the inside looking to get out. I've taken some folks out alive, and I assure you they don't ever want to go through that again.For those of us going in to get them, we are making educated and informed guesses about the chance of success based upon our knowledge of standard building construction practices and experience. Take away the predictability afforded by building codes, and it is unlikely that line officers would be as quick to send their firefighters in. And far more likely that more folks would die whether we tried to go in for them or not.It's like the standard for wind or seismic. We aren't building for every day -- we're building for that one bad day in ten years.
No, I'm not suggesting we lower our standards. Keep in mind that, as far as I know according to the code, there is not difference in using 2x material from using I joists. Sure you can span more with an 80 series 16" deep I joist than a 2x12, but from the fire protection they're equal.My question is at what point you say "enough is enough". Frenchy says he has a house with bents 4' OC when they're usually 12' OC. Well, why didn't he make they 2' OC throughout for the extra strength? The answer is that the extra cost he would incur would not likely be of benefit.The same goes for more conventional construction. Lets say you were to build a house in the Chicago area that used electricity for all it's heating needs. Many counties around Chicago mandate conduit for all electric. I don't think conduit is necessary but I do think it's safer. This house will have no wood or gas burning stoves or fireplaces in it. All of the neighbors are at least 200' away and the landscaping is the type that does not support flame very well.Is using floor trusses on this house really that much of a risk? I mean, if you have knob & tube wiring and four wood fireplaces, you're obviously more at risk to have a fire event. But the house I mentioned, replete with modern smoke detectors, AFCI's, etc. seems to me like it's pretty much never going to burn down.People say you can never put a price on human life, but those same people are happy to drive in rush hour traffic on a busy interstate or eat that super size double BigMac for lunch every day (with a diet Coke, of course).How can one know where to draw the line?
Jon Blakemore RappahannockINC.com Fredericksburg, VA
There's been a lot of #### slung around from both the fire service and the component industry about fire safety concerning floor trusses, roof trusses, and I-joists. It's sometimes hard to separate the truth from the hype and BS.The Carbeck Structural Components Institute (http://www.carbeck.org/) ws set up as a joint venture between the truss industry and the Houston fire department to study the issue and come up with some (hopefully) objective information.
Don't be too choosy or stingy about whom or how often you love.
Boss,One thing I can say for sure that is not hype or bs, is that roof trusses when they've seen a fire burn worse then a stick framed roof and are more dangerous and also the whole truss has to be replaced. When the bottom chord is burnt,you can't walk on the top of the truss, the whole truss is shot and dangerous. When the ceiling joists on a stick framed house is burnt, you can still walk on the rafters.Same goes the other way, if the top chord of the truss is burnt, the whole truss is shot and you can't walk the bottom chord of the truss.Stick framed roof when the rafters are burnt, you can walk the ceiling joists.Joe Carola
It's not really that simple. The whole truss may or may not fail when one chord burns through. Sometimes they do and sometimes they don't. Depends on the truss and the situation.By the time a board would burn through all the occupants of a building will long be dead anyway. So the omly people it will really matter to are firefighters. Sooner or later they're gonna have to give up the idea they they have to risk human life to enter burning buildings.
Opportunity is when luck and preparation come together.
It's not really that simple.
The whole truss may or may not fail when one chord burns through. Sometimes they do and sometimes they don't. Depends on the truss and the situation.
From my experience with roof trusses in fires is that when the bottom chord or top chord was burned, the whole truss failed. The point I am trying to make and have always tried to make is that, you cannot walk on a roof truss in both situations. The bottom chord of the truss is burnt and the angled pieces are also burnt, so therefore the top of the truss is sagging and failing so you cannot walk on them, period!.
When the top chord is burnt, same thing, you cannot walk on the bottom chord. It's just common sense.
You seem to be protecting the truss instead of dealing with reality or the facts. The fact is whether a roof truss is burnt at the bottom or top you cannot walk on them whether it's to put the fire out or to work on them and remove them to fix the building.
Working or putting out a fire on a stick framed roof is the complete opposite. If the rafters are burnt, you can still walk on the ceiling beams, if the ceiling beams are burnt, you can still walk on the rafters.
Also, not all situations are the same. Sometimes no matter if it's a trussed roof or stick framed roof, the whole roof has to come down.
By the time a board would burn through all the occupants of a building will long be dead anyway.
That is completely false. You obviously have no experience working on fire jobs. You can have a building where 1/4 of the joists or rafters are completely gone and that is it. All you have to do is replace that section.
The original poster asked who had experience with this stuff. This is my experience of what I've seen over the years of doing fire jobs. No one can tell me that a burnt truss is safe to walk on compared to a stick framed roof.
Have you seen trusses that were burnt top or bottom that you can walk on? Have you ever worked on a truss that was burnt?
So the omly people it will really matter to are firefighters.
Sooner or later they're gonna have to give up the idea they they have to risk human life to enter burning buildings.
Obviuosly you have issue with firefighters.
Joe Carola
Pull up your chairs, ladies and gentlemen. No wagering, please.View Image “Good work costs much more than poor imitation or factory product” – Charles GreeneCaliforniaRemodelingContractor.com
and please - no popcorn on the floor
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From what I have read, to be considered "fire resistant" a beam normally must be about 6"x8" or larger - and be designed to loose the outer two inches of the beam to char and still hold the designated load without failing. To design fire resistant rafters, the engineer that is calculating the spans on my proposed shop, he said to be considered fire resistant, he would calculate the rafter size (about 4"x12" in my case) and then add 1.8" on each side and 3" at the bottom to give the potential char zone. This was for Glu-lam beams, I assume the same would apply to solid #1 fir.
CaseyR
Actually it is covered in the old UBC, I haven't checked the new codes because I have all my permits and am in the finishing stages.
However according to the old UBC codes. timbers could be granted fire resistant status depending on factors such as wood species and size. Summerizing things without referance is dangerous but to the best of my recollection hardwoods at 6x6 were considered fire resistant while soft woods such as pine fir etc.required 8x8 to achieve that same rating..
You can confirm that yourself. set a 6x6 timber oak across a bonfire and a 8x8 pine/fir timber across the same bonfire. The soft wood will fail before the hardwood will in spite of the greater size..
Pull up your chairs, ladies and gentlemen. No wagering, please.
What's supposed to happen Huck?
Joe Carola
What's supposed to happen Huck?
Hmmm... is this a trick question? http://cdbaby.com/cd/selView Image “Good work costs much more than poor imitation or factory product” – Charles GreeneCaliforniaRemodelingContractor.com
Hmmm... is this a trick question?
No, it's not a trick question. What's supposed to happen?Joe Carola
Hello All. I rarely post on here but I have enjoyed reading all the information and the ribbing over the years. My name is Joe Sesack. I am a licensed contractor and a New York City Fireman for over 17 years. I work in an area in Brooklyn NY(Bushwick, Bedford Stuyvesant, Brownsville) that over the last 12 years has experienced a HUGE construction boom using a lot of the materials this tread talks about. Hopefully I can shed some light on a few questions. LVL is used mostly for headers where I have seen. IMO not much of a problem. Wooden I joists on the other hand are a much larger problem, but for other reasons. As someone stated before, most are covered up with 5/8 Sheetrock or double in some cases. Not a problem until the builder drills several 6-8" holes down the length of the entire bldg. to run a/c, heat, waste and everything else. Once fire enters this space, it will rapidly spread to the entire building. There have been fires in these buildings while under construction(unoccupied) with catastrophic failure in minutes. As far as trusses go, we are taught that it is the gusset plates or gang nails that are the problem with truss failure, and if we suspect truss roof framing we are to stay off the roof. Thanks for reading. May the ribbing start. Joe Sesack.
Compass Renovations. FDNY Ladder 176 343
rearmount, re: the gusset plates/gang nail plates. That information is exactly what my old man taught me when I asked him that question 35 years ago. The plates heating up , and the char on the outside 3/8 " of the wood combine to cause failure. He was a fire fighter/arson inspector/asst.chief.-35 yrs. of fire fighting.
They can't get your Goat if you don't tell them where it is hidden.
So from your perspective as builder and firefighter do you have any ideas for improvement?
I can think of a couple like blocking w/fire caulk between can lights when their position is known prior to SR (but that's kind of weak, it only takes one burn through at a can for failure) and fireblocking foam around hvac ducting running the length of a joist bay but that's weak when you condsider how many of those ducts are flex duct.
Few years ago at a home show saw a company that had a spray that made wood fire retardant that appeared to work well. Haven't heard much about it since then though.
SIr, excuse me for a moment. I have to put on my Design Professional hat on for this. Thank you.
First off, pre-engineered wood trusses are often times specified for their cost and their reasonable ease and speed of installation. (You already know all of this). The woods used are not the optimum quality and decidedly thinner than a stick built system. They can also be installed by a crew of "less than skilled" laborers.
Their physical configuration is determined by the distribution of the loading...and this goes to getting up on a damaged or burning roof...which requires each component to function as intended. One component failure and the whole individual truss is jeapodized. Frankly, anyone reading FHB or posting in this forum probably installs them only because they are forced to. Is stick built so much stronger? Mathamatically, probably not. But the resulting product is of a higher quality (IMHO) and requires a much more skilled crew.
I use wood I-beams to get the floor loading I'm looking for on long spans. But...always a but....I have never failed to require 5/8"thk fire-rated drywall on the ceiling. {For that matter all the drywall is 5/8"thk fr.}. I require fire rated wall and floor assemblies on all my residential designs. Of course, I'm not building a development home or homes either. And yes it costs more.
The community in which I live does not allow firefighters to attack a fire in the newer housing developments by a roof broach(getting on the roof, cutting a hole and addressing the source). They correctly do not need to place themselves in harm's way when such doubt occurs. These minimal code compliant structures called homes are profit sources and put up (not constructed!) quickly with little thought to longevity.
I'm glad to see that you and your fellow craftsman care about this stuff 'cause I have not had the best of luck with the developers.
ciao, ted
"They can also be installed by a crew of "less than skilled" laborers."Maybe, but I'll argue agin it.They CAN be installed, but to do it right, according to makers specs, and achieve the design standard intended, they have to be installed right.That takes some skill. Much more skill than "less than skilled" laborers possess!
Making your statement wrong.
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Piffin, somehow I knew my "less than skilled" comment would get a rise. If I may correct or clarify.
Agreed that running a pre-engineered truss system up, properly lifting and setting and aligning all of them properly, ensuring adequate temporary and permanent cross-bracing requires an understanding of what the heck you're doing. That to me is a given (I've done it and it ain't as simple as it seems).
However, in using my description I was trying to make the point that compared to doing the same roof framing in stick a truss system doesn't have to have a master carpenters understanding of story boards, supported ridge boards, continuously checking for level, properly cutting a birdsmouth, even the number and size of fasteners, etc. I've seen too, too many contractors with, with respect, kids running up a truss system. Supervised yes, final product comes out OK, but.....
I was suggesting that a stick framing system requires a higher skill level from the rough framing carpenters. I'm sure that any good carpenter can properly lay up a truss system.
ciao, ted
"When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think, as we lay stone to stone, that a time is to come when those stones will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, 'See! This our father did for us.' " John Ruskin, circa 1885. (from the inside cover of 'Audels Carpenter and Builders Guide #1, published in 1923)
That much is true. I would agree that it can take less skill to set trusses than to stickframe.I had to speak up because I have seen some real butchery with unskilled help and pre-engineered stuff.BTW, what means ciao? I see it time to time on forums
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what means ciao?
From Wikipedia, the free encyclopedia
The word ciao (pronounced "chow" /tʃao/) is an informal Italian verbal salutation or greeting, meaning either "goodbye" or "hello". Originally from the Venetian language (this word means "servant"), it was adopted by Italian and eventually entered the vocabulary of English and of many other languages around the world. The word is mostly used as "goodbye" in English, but in other languages it may mean "hello", View Image “Good work costs much more than poor imitation or factory product” – Charles GreeneCaliforniaRemodelingContractor.com
I guess you've occasionally seen the same level of skill as I have with installing pre-engr'd material.
Ciao. An Italian expression generally meaning "Goodbye and have a great day!" And, no, I'm not Italian just heard it and thought a friendly end to a conversation or post would be OK.
Ciao, ted
What a crock.
By the time a board burns through the occupants would be dead anyway? Not the case in a number of fires I've been in, friend.Depends entirely on where, size of area burning, and a zillion other variables.
Sooner or later they're gonna have to give up the idea of risking life to enter burning buildings? I doubt you'd feel that way if your kid or mom were hanging out a third floor window of an involved building, and I certainly couldn't live with not trying to save them....
I joists and trusses burn/fail faster than 2x material, in identical conditions, period. Do I fault anyone for using either? No. Do I use them? Yes. Ultimately, everything in life is weighing the odds, and odds are, overwhelmingly, that new houses are a tiny part of the total fires annually. With new electric codes, codes dictating fireplace construction and clearances etc., window egress, smoke detectors, CO detectors...........A new house with I joists is a lot safer than an old house with 2x material.
That wasn't the question tho......
I respect you and your truss knowledge, as I have lurked/posted here for a while,and know that you know a ton about trusses and engineering. You disservice yourself sugarcoating the truth.
Year Fires Deaths Injuries Direct dollar loss in millions
2000 379,500 3,445 17,400 $5,674
2001 396,500 3,140 15,575 $5,643
2002 401,000 2,695 14,050 $6,055
2003 402,000 3,165 14,075 $6,074
2004 410,500 3,225 14,175 $5,984
2005 396,000 3,055 13,825 $6,875
2006 412,500 2,620 12,925 $6,990
Not percentages, but these numbers are for residential fires. Taken from a handout I recieved at the last fire extinquisher traning class I had. They come from FEMA and the U.S. Fire Administration.
The residential structure fire problem represents 81 percent of all fire deaths and 79 percent of all injuries to civilians in 2006.
Residential structures include one- and two-family dwellings (including manufactured homes, apartments, hotels, motels, college dormitories, boarding houses, etc.
Kind of a broad spectrum, as far as what is included in residential structures IMO. Still much of what we use in single family dwellind is also used in the other listed structures.
Dave
looks like death and injuries are dramatically going down inonly six years
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I ask about too.
The fellow that was teaching thinks the decrease is due to NFPA (NEC) code changes, and the use of smoke detectors.
Dave
There are very few lvls used for floor framing. You are using the terms lvl and Ijoist intercchangeably.
Wood Ijoists do fail faster than solid lumber and firefighters do have valid concerns about them
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lvl test in progress
View Image
CaliforniaRemodelingContractor.com
is that a bathtub in the backyard ?
did the firemen rush in to save that ?
carpenter in transition