Of all the structural collapses I have heard or read about involving wood frame residential construction, I can’t remember any that weren’t caused by rot, or deterioration of fasteners.
Given the forgiving nature of wood frame construction – that is to say the components act together offering redundancy and seldom relying on a single member for support – and the fact that the design loads are usually determined by values for deflection rather than failure, that really doesn’t surprise me.
So why the huge conservatism about structure and design loads here? There are times then it seems most people here view every house that doesn’t have an engineer’s stamp as being liable to fall down into a big heap at any time.
Am I being too cavalier about the danger? Please educate and abuse me for my ignorance.
Replies
It's the CYA mentality. If your A isn't covered - C Ya in court.
What do you call a thousand lawyers at the bottom of the ocean?
A Good Start.
or that many up to their necks in dirt....
not enough dirt...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
What do you call a thousand lawyers at the bottom of the ocean?
Not even a drop in the bucket. You got any idea how many lawyers there are out there?!
jt8
"In three words I can sum up everything I've learned about life: It goes on."
-- Robert Frost
What do you call a thousand lawyers at the bottom of the ocean?
What do you call people who don't like lawyers?
Inmates:-)
Or you can do as I did which is called massive overkill squared..
honestly my walls would support a railroad train..
Just have been watching the Show, Life After People on the history channel..
They showed how just 30 years of neglect destroyed much of Gary Indiana. This was some pretty well built places too! Big Massive Churches and what appeared to be well built factories..
Many of those building were already crumbling. Falling down!
It's amazing how fast human structures begin to deteriorate once they are no longer constructively occupied. Not just lack of maintenance, but failure to maintain steady temps, intrusion of animals, etc.
The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith
"It's amazing how fast human structures begin to deteriorate once they are no longer constructively occupied"
You know it's funny, there is almost something more to it than that. Houses that aren't occupied, even when temperatures are maintained and nothing gets in, seem to go downhill in a hurry. I've had spec houses that I've built that have sat for a while before selling that seem to age prematurely. I know it sounds stupid, but it's almost as though they don't like being unoccupied.
My wife found something similar when she managed a bookstore. If you went to a section and moved all the books a bit, the sales in that area increased.
Yeah, I read an article a few months ago about an island in the Mediterranean where a resort city had become unoccupied (due to some sort of political conflict). After five years, marble was falling off the building facades, etc.
The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith
Lotsa good points have been made before I saw the thread. But I'll add a couple. Yes, I have seen structural collapses in residential and commercial construction. Like a roof collapse on a stick framed house. The roofer stocked all the shingles along the ridge. The rafters were undersized and poorly fastened to the ceiling joists. The nails pulled loose and the whole roof came down. Another job comes to mind - Not all nails were put in the hangers that hold up the floor trusses. When they pumped in the lightweight concrete on the floor the whole thing collapsed. Stick framed roofs have collapsed around here due to snow loads. Post framed buildings with roof trusses have also collapsed under snow loads. About 30(?) years ago there were a lot of collapsed roofs in the Chicago during a big snow storm.As Piffin mentioned, poor performance can also be considered a failure. Like the 2x4 rafters on my house have about 3" of sag in spots. The floor is overspanned and bounced so badly that I had to add another beam. .I agree that it's silly to overbuild something rather than making an effort to find out what is actually needed. That happens around here all too often. Throwing lumber at a problem is quick and easy, so maybe that's why it happens.
France has neither winter nor summer nor morals. [Mark Twain]
Boss Hog,
Are they really throwing lumber ata problem or seeking to add duribility?
The one thing all old buildings have in common is they were overbuilt.
"The one thing all old buildings have in common is they were overbuilt. "
That's the dumbest thing I've ever heard. Where do you get these ridiculous ideas?
Many older houses I've been in are terribly UNDER built. Bouncy floors, sagging rafters, etc. Standards now are MUCH higher than they used to be.
The smallest good deed is greater that the grandest of good intentions
Your standards are too short..
Old? Has it lasted 400, 500 , 800 years? That's old..
However you do make one valid point. Some old buildings because of a variety of factors (mainly luck) will long outlast their normal lifespan.. A timely reroofing,, misguided renovation, changing of suitablity to meet the market forces.. etc..
"You know it's funny, there is almost something more to it than that...."I agree and I suspect it's a combination of the real and the psychological. The real part comes into play when you consider all the little things you do to keep a house clean and presentable, as well as smal, otherwisel forgettable repair jobs that would have a big impact over time on the look of a house if left undone. The psychological comes into play when a house looks uncared for - without a vibrant history - it takes on the feel of a house that doesn't deserve to be cared for.
Yes, you experience it in the houses kept up by historical societies full of period furniture that are supposed to recreate what it must have been like to live in the community in the past. However grand, they always feel unconvincing and make you glad you live somewhere more convivial today.
I have seen parts of that show. It's amazing how quickly they predict that nature will take back our "improvements"."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
I think a large part of your answer is hinted at in the way you view failure.
"the design loads are usually determined by values for deflection rather than failure,"
You are talking about total collapse, but failure is not that. Failure is failing to meet intended needs adequately.
So when a floor experiences excessive deflection and vibration, it has failed.
When a roof is poorly framed and the ridge sags and wall lean lout, it is in a state of failure.
When weatherproofing systems are poorly done so that water penetrates and rot/mold gain a foothold, the system has failed.
Failure is not defined as catastrophic collapse of the structure as your title would imply.
So when we refer a person to a local expert, it is with the intent of saving them the cost of doing something over a second time, or of living with inadequacies that make a home uncomfortable or high maintenance.
often when I recommend that a person here get an engineer, it is on a situation where I THINK I could adequately perform the job with out an engineer, BUT I can't see the job and all the shared loads involved, and I do not know the capabilities of the person asking questions. It takes somebody with the training and the experience to analyse a structure ON SITE to make the best recommendations. And this is often not a cost, but an investment. I have had engineers give me solutions that are less expensive or better than what I would have come up with myself.
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after posting, I got to wondering the reverse of your question - why do so many folks have a mental block of some kind AGAINST using a professional to help them with design loads?
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$$$$ Can't say that I agree with avoiding a modest charge to get
it done right but,I believe that is the reason.
My thoughts as well. If someone wants to save money, use 1/2" drywall instead of 5/8". Skimping on foundations and structure is like trading a pretty face for osteoporosis.
Why do people not want to use professionals?
as in,
"forget the engineer, cheaper to do 4x overkill,"
Because, everyone "knows" that the professional, be it a doctor, engineer, lawyer, real estate agent, plumber, or mechanic, is simply an overpaid goon with some certificates on the wall. Why, anybody can just go on the internet and figure out how to design a skyscraper. It's easy. Don't need no training for nothin, man.
And really, if you need help, all you do is go on the net, and someone will tell you how to design your solution, without having any idea what you're talking about.
Some people have no hesitation in giving advice on how to do stuff, based on poorly worded descriptions of the problem.
When people talk about using a steel beam that weighed 1000#, that scares me - because it doesn't matter how much the beam weighs, it's what it's designed for, and what it's used for, that matters.
Reminds me of when I was a kid, and guys had this fixation on how high the numbers went on a car's speedometer. It doesn't matter how high the numbers on the speedo go, that's got nothing to do with how fast the car will go.
Very well said.Based on some of the quotes you used, I'm thinking there is some cross thread commingling on this topic from here
http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=119480.18In that thread, I know from Workshopjon's past posts that HE is perfectly capable of doing his own calcs, but it seemed irresponsible to project his own ability onto a DIY with who knows what background and assume they are as capable as he is
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Of course you're right but keep in mind that every bridge, stadium, building, smokestack etc., that fails has been designed by an architect and/or engineer. I have a great engineer but he tends to over engineer a lot of projects. I put a set of simple stairs in a store one time. He called out 2 8" X 8" wood posts to hold the 5 foot long header on each side.
Piffin.
Let me answer your question. Not for everybody but for me..
The reason I didn't use a professional to design my home is I wanted a massive overkill look..
I was impressed by the size of timbers in old barns that stood the test of time and vowed to replicate them.. That produced safety factors off the chart.. when added together with the use of ICF's and SIP's my numbers started to approach that of railroad bridge engineering..
In fact massive overbuilding proved far less costly that a bid done by a professional.. (also a whole lot more fun and satisfying)
To answer your second post first, avoiding engineers by overbuilding drives me wild. There is an elegance to appropriately designed structures and if it takes an engineer to design them then I am all for it. Simply beefing things up to avoid finding out what would be necessary doesn't qualify as Fine Homebuilding to me. This isn't an anti-engineering thread by any stretch. I just think it is empowering to understand all aspects of what you are building without being afraid of the results.
I take your point about failure rather than collapse. I guess what prompted this topic was what I see as inappropriate structural responses to failures that are not caused by real structural inadequacies in the first place. Take the recent huge emphasis on deck ledgers. I would venture that the great majority of deck collapses are due to water infiltration or rotten posts. Yet the most common response seems to have been to beef up the structural connection of the ledger to the house - to resist lateral loading that would only occur then some other part of the structure failed.
What do you think the percentage of the necessary structural remediation that you do when you are adding to or renovating the houses you work on is necessitated by deterioration and what by structure that has failed due to undersizing?
Speaking as an engineer...Engineering costs money too. There's a grey area in-between over-engineering and over-building.Imagine what it would cost to have an engineering analysis done of an entire house, so that each stud was optimally placed and no more studs were used than necessary to achieve design strength. Not only would the engineering be expensive, but it would be more expensive to build since every dimension would be different and there would be no modularity.Re decks, there was a rash of deck collapses about ten years ago, with a number of fatalities. In virtually all cases the failure occurred due to overloaded/inappropriate fasteners, sometimes combined with simple overloading. The result was that codes were changed to anticipate more overloading and to more rigorously specify fasteners.
The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith
That probably half and half. Some from rot and some from poor structural design.Here are a few photos from yesterday for example that just happen to include both. Poor detailing let water in to cause rot, but at the base of the first, you see a 4x4 stub tilted over. It was just propped in there and not supporting a thing. I believe they assumed the pier to the left was supporting things, but the joint was no way tied together. This is a house that has been added onto about 8 times. Some by DIYs and some by 'pro's. It's been obvious that they all could have benefited from professional advice.The third photo also shows both rot and bad foundation. We already replaced the pier there. The crete went down only about 28" in a location where 48" is required, and was just a big blob of crete the shape of a wheelbarrow. They had dug a hole and slopped the crete in. So frost had rolled it off to the side and had a 30° tilt to it.I could go on and on, but these were interesting and fresh in my mind as examples of BOTH the kinds of failure you mentioned.In that first, The house was not catastrophically falling down, but the interior door there would not close properly, and trim such as crown molding was splitting wide open at a intersect with bookshelves installed to that wall.
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What are those holes on the wall in the second pic? insulation, venting, purple martins?http://www.tvwsolar.com
Now I wish I could give Brother Bill his great thrill
I would set him in chains at the top of the hill
Then send out for some pillars and Cecil B. DeMille
He could die happily ever after"
It is the tall wall of a shed roof 1/12 pitch.
That was somebodies attempt at venting the attic space with pop-in 2" plug vents
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Are you doing a rehab? How will you handle that attic? "Hot" roof?http://www.tvwsolar.com
Now I wish I could give Brother Bill his great thrill
I would set him in chains at the top of the hill
Then send out for some pillars and Cecil B. DeMille
He could die happily ever after"
I might have mentioned, the place ha been added onto at least 8 times, possibly as many as 12. So there are overlapping roofs. We will be getting into the space to open airflow between sections and blowing loose insulation in after sparky finishes his thing. Then adding some regular roof vents to various places on the roof to take exhaust out. The low side of the shed roof has soffit vents in coming. It is a sun room that used to be a screened porch and really gets hot in sunny weather.I'll find a couple pictures to help you visualize things.......later - right now, this site is being a PITA about accepting photo uploads.
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fingersandtoes..
I'm sorry there is a certain elegance to over building something as well. My favorite is barns.. Walk into old barns that have stood since before the civil war and the one thing they all have in common is being overbuilt.
At least overbuilt in the sense that the same space could have been enclosed with much less wood..
However the issue of durability enters here.
If you look at the really old homes in Europe.. the ones that have endured two world wars, economic depression, changes in needs. and fashion. The one common factor they all have is being overbuilt.
I'd love to have met the person who said building a durable home that will long outlast me is my highest priority. It's not getting the biggest bang for my buck. It's not a simple intellectual exercise it's a statement that I will sacrifice today for the future.
I see more sagging barns that are falling apart than massive beautifull over built ones.once again, you are over generalizing based on the half dozen barns you like for one reason or another.There should be a Federal mandated warning label on your lips when you speak especially when you start a phrase, "They all..."
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Word police again Piffin? I thought we cured you of that..
Oh well, yes you are correct some barns that are underbuilt survive.. as do some houses. Mainly a factor of luck and not engineering..
Here in America we consider something a mere 50-100 years old as old.. I look at homes that are 400- 600- 800 years old in Europe and hold a differant opinion of old..
I've often wondered why you didn't build your house out of stone.
Didn't you see my pictures? Go to 85891.1 & 94941.1 and scroll through, you'll see lots of stone work (I'm very proud of since I did it myself)
Because of expense and over design.
I'm an architect/sometimes builder, fairly well versed in wood and steel beam construction design but at the same time, not a structural engineer.
When I'm doing a one of a kind (custom) house, have a steel beam that has maybe a cantilever or a concentrated load, I calculate it out and usually bump it up a notch or two. Better to do that and have the beam cost an extra $150 then get an engineer to look at thing for $700.
Now if the house is for a developer/builder client and he's gong to be building the thing 30 times, if there's unusual loading like that above I get the house engineered (by a guy who understands residential construction-that's very important) because even $150 can add up in a hurry.
Runnerguy
"Better to do that and have the beam cost an extra $150 then get an engineer to look at thing for $700."Now you aren't figuring any money for your time to do some calcs to arrive at that.So say your time is worth $100 added tot hat $150 extra beam cost, then add another hundred for liability risk. Then suppose your engineer can do that assessment for $350.Where is the gain in DIY engineering?
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You're entirely correct. Nor did I figure in my time calling up the engineer (and half of the time, leaving a message because he's not in and going the phone tag route), emailing him a set of plans, calling back two days later wondering how's it going, a phone call from him with the usual follow up questions when his finally gotten around to it and has it in front of him (and maybe more phone tag). And the one job in ten where he's given me a lean 12" deep beam as the solution but we only have a 10" thick floor (shown on the plans) and I have to explain we need a heavy 10" beam and not a lean 12" beam. All that may not sound like much but we're comparing it to "time to do some calcs" which isn't really much either.
Either way, I'm spending time.
And as the architect, my liability ain't goin' away if I know attorneys at all.
Runnerguy
LOL, Good points.
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You bring up an interesting point. I think the differing points of view stem from a different set of expectations. The conservative side sees the best way as the only "correct" way. The more forgiving side sees multiple possibilities & definitions of success.
Imagine a person's "problem" was needing to get to commute to his job 2 miles away. One solution would be to build him a car. Another solution would be to build him a bicycle. 98% of the time the car solution will be overkill. 2% of the time the bicycle solution will be problematic. Some people see the 98% as unforgivably wasteful, while others see the 2% as unforgivably cavalier. It all depends on your point of view.
The bigger problem is when one become dismissive of the other's point of view. That tends to be a common occurrence here in "Fine" home building when overbuilding tends to become the primary characteristic of "fine".
Personally, I think a fine house is best judged by its degree of usefulness.
Of all the structural collapses I have heard or read about involving wood frame residential construction, I can't remember any that weren't caused by rot, or deterioration of fasteners.
Ever read about the structural damage that occurs in hurricanes? It's a mistake to build for average conditions. We should build for the once-in-a-lifetime storm, flood, seismic event or other manifestation of Mother Nature's wrath. After Hurricanes Hugo and Fran, North and South Carolina adopted much more conservative codes. They have worked.
Well said!
To a large degree, it is not the stricter codes that help as much as the stricter enforcement. Studies analyzing both areas after storms found that the failed structures were predominantly ( by far) the ones where the nailing done was not according to required schedule.
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You are right about the forgiving nature of wood frame design.
If we design to the current code using the ASCE 7 protocols, with snow loads per the maps, calculating the factors for drifting, increase factors for higher elevations, etc., we end up with specs like 2x12s on 12" centers, in certain cases.
And we'll build this new thing right next to some old farmhouse that was built in 1882, with its roof being framed in rough cut rafters measuring maybe 2x8, similar spans, centered at maybe 18 to 20 inches.
But every age has had its span tables, its rules of thumb, its pattern books, something of some kind to guide the builder. That is not to say that mistakes did not get made, or that builders used data and did not just go from the seat of their pants.
The reactions here like, "Hey, you better get an engineer," are usually made to the clueless, those with little to no experience, who blunder in here with a question posed so that it is clear they are unqualified.
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"A stripe is just as real as a dadgummed flower."
Gene Davis 1920-1985
"The reactions here like, "Hey, you better get an engineer," are usually made to the clueless, those with little to no experience, who blunder in here with a question posed so that it is clear they are unqualified."That pretty well sums it up.
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I resemble that remark!"There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves."Will Rogers
My impression is that the majority are due to overloading of fasteners, either from poor design or from stupid things like a large wading pool on a spindly deck.
You are right that the standard wood frame construction techniques used in the US basically don't even need fasteners, except to "peg" pieces together to keep them from shifting over time. The basic framing paradigm is that wood bears on wood, through headers, jack studs, etc. (There is an exception for roof framing, where fasteners may be in shear to prevent rafter ends from splaying outward.) Failures occur on decks, roofs, bearing walls replaced by beams, etc, where fasteners are actually expected to carry structural weight.
we're working on one now with bad footings from 1982
we had to jack the main beam 3" to begin our work