Thought some of you would be interested in reading about this firehouse roof collapse:
http://www.uticaod.com/archive/2003/02/19/news/16785.html
There are some pictures here:
http://www.uticaod.com/news/photogallery/projects2003/sauquoit/sauquoit.htm
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Guess this scene was repeated all over the northeast in various types of structures, with the recent snows. Here are a few more:
http://www.herald-mail.com/?module=displaystory&story_id=49877&format=html
http://www.herald-mail.com/?module=displaystory&story_id=49877&format=html
Failure is not an option. It comes bundled with the software.
Replies
Curious as to your thoughts on snow and design and this failure.
Well, I have a lot of thoughts when I hear of things like this.
I think of guys I've seen on jobsites who cobble something together, then stand there with their hands on their hips and proclaim: "That ain't goin' anywhere".
I think of guys calling in here asking for a beam for something or other, and saying: "It doesn't really carry much of anything".
I think of that thread a while back someone started here saying we didn't need to worry about structural problems, since houses never collapse.
I think of all the half-a$$ed prints we get where no one has really given any serious thought to structural design. But they throw the things up anyway.
I think about how much this is costing the insurance companies, and how those costs are going to be passed on to all of us. And how much of those costs could be saved if things were done right in the first place.
I think of the times I've told someone something they didn't want to hear regarding beam or truss design, and hearing them say: "You're just being conservative, and trying to cover your own tail".
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Sorry if I went off on a tangent there. You just kinda hit a hot button.Tell me what you need, and I'll tell you how to get along without it.
Your comments ring true, especially the one about the half-arsed prints. I'm surprised how many large and expensive structures get built with them. There's often lots of paper generated but it doesn't have much to do with the quality of the prints. "If you can't dazzle 'em with brilliance, baffle 'em with bs".
Good post, Ron. From my own perspective, this will be a legal mess between the insurance company's subrogation department vs. the GC, truss manufacturer, architect, design engineer, etc. It's not that we are looking for a way to get out of paying, it's just that we don't cover materials or workmanship, or design flaws.
There's almost always a carefully explained limitation on collapse - it is basically a covered peril if the collapse is from the weight of rain or snow, but there are a couple of "outs". ie, " faulty, inadequate, or defective, . . . . design, specifications, workmanship, repair, construction, renovation, remodeling, grading, compaction . . . . materials used in repair, construction, renovation or remodeling, or maintenance. "
Folks, this is one reason Boss says not to alter a truss, and to get an Engineer to sign off on a repair. CYA !
Greg.
I think of the times I've told someone something they didn't want to hear regarding beam or truss design, and hearing them say: "You're just being conservative, and trying to cover your own tail".
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Sorry if I went off on a tangent there. You just kinda hit a hot button.
I know what you mean. I told one buyer the electrical system was so screwed up I personally wouldn't spend one night sleeping in the house. Four months later I got a call asking for a copy of the report because the original burned up in the fire. They hadn't quite gotten around to having the elctrical systemn repaired.
_______________________
"I may have said the same thing before... But my explanation, I am sure, will always be different." Oscar Wilde
This didn't look (from the pictures) as if the truss failed. It looked as if the truss joint at the existing structure was the problem. Unfortunately the lower wall wasn't pictured at the right angle to determine if it kicked out at the top allowing the trusses to land on the red metal supports. The gable end bowed out a bit but that didn't seem to be a factor..
It makes you ponder all those little pieces of galvanized sheetmetal we use. Sometimes it seems like such BS, but joints in tension need all the help they can get.
Nice post.
"It looked as if the truss joint at the existing structure was the problem."
Could be - I don't really know. But you indirectly make a good point - Doesn't matter how strong the trusses are if you don't support them adequately. I have never once (in the 18 years I've been at this) seen a joist hanger installed according to the manufacturer's specs. Most of the hangers I see installed have roughly half of the required nails in them.
Don't know if that's what caused this particular collapse, but it's possible. Am I getting smart with you? How would you know?
Well yes, the nails in quantity are an issue but also the selection of the nail is strange as well. Memory is weak but I think it is a #10 that is 1 &1/2 inches long? Not only was it a strange size it just isn't available except if you buy it where the Simpson or other ties are found. I tried getting them at the local Ace or true Value and I was greeted with a blank stare.Jack of all trades and master of none - you got a problem with that?
The majority of hangers require 16D common nails in the supporting member.
The short nails you mention are called "Teco" nails around here. (Don't know why) They can be used in place of the 16D in some cases, but the capacity of the hanger is reduced. All lumberyards around here have them. So do some of the truss plants.
BTW - If a truss manufacturer sends you hangers, they should also provide nailing requirements on request. Or you can ask for a hanger catalog and figure it out fer yourself. There are very few problems that cannot be solved with a suitable application of high explosives.
>> There are very few problems that cannot be solved with a suitable application
>> of high explosives.
Yeah! If we could use avalanche guns on our roofs, a lot more guys would be out there after every snow. "Gotta make sure we don't get any weight buildup on the roof, honey."
Here we call them "joist hanger nails". They're used where the sheet metal piece goes against a piece of two by with nothing on the other side. Otherwise, you'd have long ends of nails sticking out. We call those "shiners".
It's especially bad that this happened to a fire station. If snow causes other structural failures around town, it's likely that some will result in fires, and that truck is disabled right when it's needed most. For that reason, our fire department parks their equipment outside for a few days after an earthquake.
-- J.S.
Your a more power kind of guy right? :)
What do you think of the nail guns made to use with hangers, the ones where the nail protrudes out so it can be set in the hole of the hanger?
Looks really cool, but I don't think I do enough work with hangers to make buying one a legitimate purchase, just wondering if you have ever used one?View ImageGo Jayhawks
I started to use the hitachi hanger gun when hurricane clips became standard in the area about 6 years ago.
They do work well and speed up the process quite a bit. Only thing that I don't like about them is that they don't have the same hold power that the hand nails do ( I'm speaking of tensile not shear )
The garage of my company's Princeton, NJ office collapsed. A couple of the structural engineers noticed that the snow on the top level was plowed into a large pile in one corner. They moved their cars, noticed cracks in the precast concrete beams and called the building managment. The structure collapsed while the engineers were explaining to the maintenance crew what they did wrong and why they shouldn't drive on it with their trucks....that's not a mistake, it's rustic
I was rebuilding a deck in CO when next door, the village handyman was shoveling off a roof on a simple 4/12 gable on an older house that had about three feet built up. It was early spring so this represented a winter's worth of compaction.
He got one side finished and went to lunch.
When he got back to the job, the uneven loading had collapsed the roof and knocked out a wall, pretty much rendering a summer cabin into a summer's worth of campfire wood.
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Excellence is its own reward!
Commercial building's low pitched all metal roof down south had an interior gutter system. Didn't keep the gutters cleaned and one plugged up making a swimming pool up there. Total collapse.
I like the idea of the "Hanger guns", but have never used one.
I tried to talk my boss into buying one, and renting it out on large jobs with lots of hangers. No luck so far.On the keyboard of life, always keep one finger on the escape key.
If you get accurate enough a Paslode IMT will sink it thru the hole in a hanger. I got it down pretty well. You gotta align it but it works well. Obviously this isn't for the squeemish nor does anyone attest it is safeJack of all trades and master of none - you got a problem with that?
Are the nails that that gun uses the proper diameter ?
Usually gun nails are a little smaller dia. I'm not sure that useing them in hangers is kosher.
I used what was available, and you could be right. Most were the 3 1/4 inch rosin coated spikes. In a critical application (public building) or stressful connection (limits of materials) you wouldn't want to vary. In my case I built so over the top for my own structure it wouldn't be much of a factor. But for all you lawyers out there, my name is Newf ;-) Jack of all trades and master of none - you got a problem with that?
But for all you lawyers out there, my name is Newf ;-)
Now if I was Matt, I'd say...blow me!
If I was Mike Smith, I'd say ...bite me!
But I'm me so I will just say...GTAFFAARD!
...<g>...
Keep your stick on the ice...Peace
Newf
Correct me if I'm wrong, but hasn't the fine line between sanity and madness gotten finer?
George Price
View Image
Yea, well It's hard to be anonymous when your name is on the header. Thanks for the invitation for a taste but I just ate. Gtaffaard?
Speaking of anonymity, how long do our bits o' wit and confession to substandard construction stay on the Prospero network? I think I know the answer when a meg of HD memory costs about a buck... forever.
Jack of all trades and master of none - you got a problem with that?
Once on the 'Net, it's there forever!
GTAFFAARD...Kurt Vonnegut Jr. Breakfast of Champions ...Something to do with doughnuts, flying, and sex!
...<VBG>...Peace
Newf
Correct me if I'm wrong, but hasn't the fine line between sanity and madness gotten finer?
George Price
View Image
Why don't the home owners and business clean the snow off the roofs a few times a year. Home owners for the most part have pitched roofs and can see how much snow is built up.
Business (commercial buildings) is a little bit different with the flat roofs but still you would think they would be checking after a year of heavy snow fall.
You can design a roof to carry 100" of snow load but if you get 200" of snow on it, it will fall down.
Where is the TV news. Why weren't they reminding people that roofs should be check for snow? If you have 12" of it you should be getting it off of there.
Fredsmart,
A couple of responses to your statements.
You don't design for inches of snow, you design for pounds of load.
Sometimes that loading happens to be snow but snow can have a wide range of weight per inch as you surely know if you've ever shoveled any.
Personally, I don't advocate shoveling it off in most circumstances. In my twenty years of roofing, I saw far too much roof damage and shortened life spans on roofs that had been shoveled by people who didn't know what they were doing. People fall off roofs doing it and get hurt.
In some high snowfall locations, snow is shoveled regularly by roofing pros but that is more to keep it from sliding off and hurting passersby.
IMO, it is underdesigned roofs that cause most failures from snow load. The rest are caused by carpenters who say, "We don't need that item. Those guys were just overdesigning to justify their existence. Cut it out"
Buildings designed with flat roofs in Texas and built in the snowy north are good candidates for shoveling when there is a heavy deep wet snow..
Excellence is its own reward!
IMO, it is underdesigned roofs that cause most failures from snow load. The rest are caused by carpenters who say, "We don't need that item. Those guys were just overdesigning to justify their existence. Cut it out"
I heard an interview yesterday with someone who wrote a biography on the 17th century architect, Sir Christopher Wren.
The author told one story about how some clients had insisted that he needed to add some support for some particular soaring structure, which he believed wasn't necessary.
So he had the stone mason build the column, but stop a foot short of the top!
_______________________
"I may have said the same thing before... But my explanation, I am sure, will always be different." Oscar Wilde
After the collapse of the first Tacoma Narrows Bridge, Othmar Amman was pressured to modify the newly opened Whitestone Bridge because it too relied on fascia girders instead of stiffening trusses. Amman insisted that his bridge was designed correctly and did not need the trusses. Eventually he yielded and built diagonals and top chords on top of the girders. Until an inept 80's retrofit clamped the main cables to the trusses at midspan, the trusses were decorative. ...that's not a mistake, it's rustic
ToyRus had a roof collapse today.
It sounded like to much snow that had not been cleaned and then today it rain. Lost a lot of roof.
What bugs me is how avoidable this whole thing is. Having weather--snow, quakes, whatever--affect the response abilities of emergency workers because the garage is unstable is ridiculous. It doesn't have to happen. There are ways to build that are safe and cost effective, and the stuff I mess with is not the only way, so it's not about promoting one over the other. Just plain nuts.
> There are ways to build that are safe and cost effective,
Yes, it dawns on me now that those quaint Scandinavian villages where everybody has very steep roofs and the doors are always on the gable ends of the houses aren't that way because everybody wants to be quaint and picturesque. It's because they want houses that don't collapse or dump snow on their heads. ;-)
-- J.S.
That is the kind of overlooked simplicity that will be the ruin of our society. Like the archaeologists who for years, could not figure out how the Egyptians got the pyramids so perfectly square, until a carpenter taught some of them about the 3-4-5 rule....that's not a mistake, it's rustic
>> That is the kind of overlooked simplicity that will be the ruin of our society.
I take it you mean the overlooking will be the ruin of our society, not the simplicity?
Hah, yeah, I should try sleeping instead of reading these threads. I'm glad you read what I meant instead of the impaired typing....that's not a mistake, it's rustic
Here's a followup story on one of the collapses:
http://www.gazettenet.com/03112003/schools/4132.htm
Doesn't take long for the finger pointing to start.
I am grateful that I am not as judgmental as all those censorious, self-righteous people around me.