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I recently vaulted the ceiling in a room located under the hip of a 4:12. The house was built in 1957, so its structure was obviously questionable, but, how off were those guys?? Going by rules of thumb and eyeing what might work or not?? I ran the plans by my structural engineer, only to have major changes…. big surprise?… Apparently the existing 2×6 hip, spanning 17 horizontal feet and the 2×6 rafters were not supporting the roof. HMMMM… So, its been standing for 50 years or so, my engineer directs me to add triple 14″ micros. I can understand 2×10 rafters, but triple 14″ micros, that was a bear. Now we have lost almost a foot of headroom and spent 300$ on one beam. My question is: What standards do engineers go by: 1. What will work. or 2. What they will never get sued for building because the American legal system is not quite plumb?? I vote for the second, what crazy shit has your local enginner made you do? Not too mention inspectors, but that is another topic.
ZAP
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Dear Isaac,
This could be fun.
We won a contract to do some work on a 200 year old church. It was obvious from the attic that the original flat ceiling had been ruined by condensation and a new sloped ceiling was built under it. An engineer was hired to assess whether we could dump 8000 pounds of insulation onto it. He said it was ok. The only trouble is that he never looked at it. Climbing down into the structure, we discovered a third sloped ceiling below the one he "checked". I made sure his bill didn't get paid.
Contrarily, I hired an engineer this summer to help me size steel to support a large cathedral ceiling. This was a renovation where we wanted to remove a post, placed in the center of a 38 foot span. We worked together to get a workable solution: 2 14" x 38# channels. It wasn't much fun dragging 40 foot 1500 pound sticks into an existing home and lifting them to the peak, but it was possible.
The engineer listened to all of the process concerns I had and incorporated them into his stamped print. It was a very productive collaboration worth every penny to me. Lived to tell about it.
Cordially, Fred
*Issac, I think engineers are like those of every other profession. There are good ones and there are those that do their job poorly. (Contractors too!) From what I've seen, the best engineers structural or otherwise are the ones who have just as much field experience as AutoCadd time and they are able to see what works best in a particular situation and what doesn't. Either way they are making money especially here in my area (Florida) where almost all jobs requiring a permit, now need an engineer's stamp on the drawings. Guys (and gals) are making big bucks just reviewing and approving blueprints. Kinda makes me want to go back to school???Mike
*Engineered Construction: No "rules of thumb", or "Hail Mary construction" (build it then pray). Likely a very significant safety factor too. The home I presently live in was built by an engineer in '74. Double garage door header is site built plywood/2x4 plate truss (didn't use the standard doubled 2x12's which were so common). Mine is only garage door header in area without the typical sag (the "smile"). Would I have an engineer design my home? - nope. Couldn't afford to build it.They sure are priceless for work described in thread or if you're placing a point load on an existing foundation or for countless other situations where analysis lets you sleep well at night.In residential arena would be nice to have engineering done with architecture in mind. Engineers are not necessarily architects and vice-versa. Some thoughts. Randy
*I had a similar experience last summer. Existing flat roof full 2x4 fir with 1x12 sheeting ran at a 45 degree, like a floor. Room was 14x13. Roof was spongy, sagging, but still standing. Home owner wanted a 4x4 fixed pane skylight in the center of the room. Engineer called out 5.25"x11.75" PARA LAMS set on 4x4 posts with 14 inch x 30"x30" footings. Wasn't laughing while I set them, I stepped back and chuckled. Looked like I was preping for a few more stories not a skylight I could carry to the roof myself. Also called out on the plans was to preload all four footings. Must have owned some trust joist stock.
*Isaac -I've said it before, but it's worth repeating: "An engineer who agrees with you is smart - An engineer who doesn't agree with you they're a moron".I'm not exactly sure what your beef is. You said the structure was questionable, but don't think it should be beefed up? Spanning 17' with 2X6 lumber seems nuts to me. So what criteria did b youuse to arrive at the conclusion that the engineer was wrong? Seems you "designed" the thing just by looking at it relative to the old structure. And the fact that it stood for 50 years isn't particularly significant to me, for 2 reasons. First, I imagine there's quite a bit of sag in rafters that long. No way would that be acceptable by today's standards. Second, they may have just been lucky so far. About 2 years ago, we did trusses for an old stick frame roof that had been there for God knows how long. When it came time for replacing the shingles, they started stocking bundles of shingles along the ridge. Wasn't long before the whole roof colapsed under them. Reroofing aside, you never know when you're going to have that one huge snow which might cause the same thing. So what criteria do I use when I design stuff? First comes experience. About 2/3 of the time I have a pretty good idea what's appropriate and what isn't. Then I go to beam charts or software to determine what works. I try to look for least cost options, as well as what's easiest to install. Sometimes there are other limiting factors, like headroom that must be taken into account. Sometimes, customers and/or salesmen call and question what I've called out. I don't look at this as a personal attack, (Unless they're jerks about it) but answer their questions and tell them why I did what I did. Sometimes I upgrade to something that's borderline, or has a bit more deflection than I'm comfortable with. Sometimes they agree, sometimes they don't. But I think that dialog is important. Did you talk to the engineer to see what his reasoning was?Gotta get to work, or I would be happy to discuss it more. Maybe I'll add more later...
*Wanted to add a couple of notes after I reviewed what I wrote early this morning. First, I'm not an engineer. But I do a lot of "engineering" work - Designing trusses, beams, and such. Also - I had a line in there that didn't make sense:> Sometimes I upgrade to something that's borderline, or has a bit more deflection than I'm comfortable with.What I meant to say was that sometimes I upgrade i fromsomething that's borderline to something better.And as for your comment: > 2. What they will never get sued for building because the American legal system is not quite plumb?? This is partly true. But don't i youworry about things that will geti yousued? So why shouldn't an engineer?BTW - Did you know that there's no statute of limitations on engineering? So anyone who owns that house can sue the engineer over his design for as long as the structure exists. Engineers have good reason to be a bit paranoid.
*I agree with Boss Hog, about everything in those posts. If you want to open up a ceiling in your underbuilt house, you've got to compensate for:-Stress on the already weak structure-Changing structure that may be supporting the above-Carrying loads with what you've changed it to.Yes, an engineer may err on the side of safety. That is something we should all strive to do. Your house may just be waiting for the right combination of environmental/load characteristics to create a failure, which could be catastrophic if you help to further weaken the structure.MD
*Isaac ---I think most of the comments missed the engineering issue here.You changed from a roof that had thrust support at the rafter ends to one that did not. This changed the ridge from a non-load bearing ridge to a load bearing ridge. this also changed the exterior wall loading from a uniform load to concentrated loads where the load bearing ridge ended. ...I am an engineer. I am proud of it.I don't ever over build - I would not have any business if I did.
*Our house was designed by a structural engineer and I believe he designed it for a worst case scenario. In other words, our snow loads are 75 PSF and our wind load is 50 psf. I think he designed the house to withstand BOTH those worst case scenarios at the same time? So you know, a huge snowstorm in a hurricane followed by an earthquake! LOL! That's okay with me, but it was expensive to build. He also designed 24 inch footings on solid bedrock, but that's okay too. I'm hoping the house lasts for many generations and I'm glad to be building a solid house. I never thought our engineer was being unreasonable or trying not to get sued. He just wants his stamp on well built homes. Like any profession, so much depends on the individual.Paula
*I just wish our engineer would have talked to our architect! We engaged an arch./engineer firm to design our addition with the only stipulation that ceilings and floors needed to match with the existing house. That means that they had 9 1/2" between floors for a 23' span beam (to hang the floor joists on). The arch. drew it as a clear span with a single 9 1/2" beam, the engineer changed it to 16", but that didn't make it onto all of the drawings - so there was no notch in the foundation for it and we didn't want a step up to the new room. When I called the engineer about it he suggested that we notch the ends of the beam. Which to my uneducated brain sounded kind of dumb - doesn't that just change it to a 9 1/2" beam since that's all there is on the end? Instead we switch to lvl's, added a midspan footing and threw in a support column (all checked with the engineer). It would have been nice if they had communicated to each other (they were partners) so that we didn't have to make major design changes midstream.
*Amy, your architect is responsable for coordinating the Engineer's design with his own. That is, if the Engineer was a sub-consulttant to him. Meaning the Engineer was contracted directly to the Architect (typical), and not you. That beam depth problem is what we design professionals call "Errors and Omissions". In fact there is liability insurance sold to cover problems like that. Sorry to hear about the late "design" changes....architects are supposed to prevent things like that.
*> The home I presently live in was built by an engineer in '74. Double garage door header is site built plywood/2x4 plate truss (didn't use the standard doubled 2x12's which were so common). Mine is only garage door header in area without the typical sag (the "smile"). Randy, could you post a sketch of this plate truss? It sounds like something that everybody would want to use if they knew about it.-- J.S.
*Taking a picture of a homemade header isn't enough. you would have to have lumber grades and sizes, fastener requirements, etc. And you would have to know how much load it was capable of carrying. Just buy an engineered beam - Probably less expensive and better anyway.
*Michael,Industry reports I've read cite typical profit margins in the range of 6% to 12% for engineering consultants. This certainly doesn't seem too inflated to me, and is much smaller than some of the margins I've heard builders toss around.
*Isaac,I agree with prior comments in that there's some good, some bad and many mediocre practitioners in any job.What standards do engineers go by? First, engineers try to constrain themselves by physics. You know, make sure gravity never proves too much for that roof over your head. Quite often, these real world rules are also codifed as a "building code" or "law". Not too easy to simply change these codes (or gravity for that matter).How did that code get developed you ask? Largely from experiment, experience and theory. Sometimes also from watching failures resulting from erroneous rules of thumb or eyeball designs. All structural codes have some type of factor of safety built in. Ask the person who's going to live under that roof if they'd rather spend that $300 and be safe, or risk a big snow load collapse of those 2x6's.
*What surprises me is how much engineering work is done sight unseen, or seen very little- "mail order" engineering; projects where the architects/ engineers are on the other side of the country. I do think a good engineer is worth his weight in gold ......... many of problems would be eliminated before they start. How many times have we heard "we've always done it that way"?
*So much to respond to -so little space and time...on the original problem-By hanging a vaulted cieling in under, it is possible that you entirely change the forces working here. You lose the collar tie effect of the old cieling joist. You might be adding the weight of the cieling and insulation to the roof rafters. You were marginal at best to sytart with. That said, tripled 14s for that span does seem excessive. When my engineer comes up with something that sound out of the ballpark, I just ask him if he needs to double check something in his calculations. He doesn't mind and generally can immediately explain what it is I am missing but once he did find an error toward overkill in his own design. Another time I asked if he wouldn't mind beefing things up at a certain point that I was instinctively concerned about and he gave me options how I could do it.I would far rather work something out with an engineer than with an architect anyday. Arch's are artists with ego gratification problems and control issues as a general rule while engineers deal with materials with known qualities - something you can count on.
*George, I need advice. I hired a engineer a few years ago. I needed a structural design for a spec house. the lot used to be a pond years ago before the development. We use Monolithically poured slab foundations with perimiter and internal grade beams. (called waffle type if that helps). He said that he needed to perform a soils analysis. I agreed. He sent his guy to drill and recover the samples. Then he sent me his contract. He had a clause that basically said that he was not resopnsible for anything. Furthermore that i would indemnify and hold him harmless even if he were found negligent. When I hired him I was very clear that I wanted him to provide me with a design, and inspect the set up and rebar placement so as to insure what we were building exactly what he had designed, and that I was willing to pay whatever his rates were for all of this. Needless to say, we had a big problem. I would not sign that agreement, and he did not want the resopnsibility for the structural integrity if the foundation under my terms. Was I asking something from him that was unusual or was he just used to drawing pictures and never having anything to do with them after they were built.
*So isaac - Are you still around, or are we just talking to ourselves ?
*Leigh,First, I'm not an attorney. But, seems like I remember being told that in most states it's not possible to be indemnified against negligent practice. Any attorneys out there?
*Whats up with structural engineers?? Everything: - it's anything that's DOWN after it's up that's a problem.
*Issac,yeah, engineers worry about being sued, because they will be. Engineers & Architects are liable for their lifetime,(and in some states their heirs are still liable). Never mind that someone pulled out the ceiling and now that old 2X6 ridge is suddenly a structural ridge. Hell, I'm worried about my neighbors kid falling off our tire swing and sueing us.Piffin - all Arch's aren't egos. I'm a residencial arch, and I do what my client requests (within code). If they want 6 Palladian windows across the front of their Queen Anne, fine. (but I will try to talk them out of it.) I calculate most of the beams in my structures. I calculate beams according to minimums set by my state codes. (but I'll be calling an engineer for any non-typical condition.)
*Renaisance Kathy,Sorry to step on your toes. Note please that I did say..."as a general rule"I am indeed awaaaare that there are many humble and very good architects out there. None of us are perfect but it seems to me that the field of your chosen livelyhood has a higher percentage of egotistical practitionersthan the general population. My intent was to point out that their point of view is more artistic than that of mathematical engineers or hands on builders.Welcome aboard, we need more realistic ones.
*Leigh,This is a standard clause in engineers contracts. Every soil report that I have seen from a geologist says something similar and so the structural engineer has to qualify his/her design also. If the engineer is state certified and has a reputable track record I would have no hesitation about accepting the clause and moving on. It sounds like the engineer proposed a floating slab that would limit differential settlement.
*Mike,Are you saying you've seen indemnification against negligent practice as a standard clause? If so, does this mean it's held up in court in your state?BCK
*My contracts say: based on what I am told, the solution I provide is correct.Of course, I am not responsible:for deviations from my design, ormaterials or workmanship that do not meet the design assumptions.This is similar to my wife's CPA business where she accepts responsibility for her work (and pays the interest and penalties when she is wrong), butis not responsible for the clients actions.Good preofessionals accept responsibility for their work.
*Mike, being a standard clause doesn't make it right. (I know I'm rocking the boat) Picture this, I include a comparable clause in my sales contract. Assuming the buyer reads it, I dont think that I would ever sell anything. I know that he is only selling a service and I am selling a product. My line of thought is this. I wish to A. do the right thing (i. e. build it strong enough to withstand the gravitational and geotechnical forces that will surely act upon it over the years), and B. limit my liability by paying a professional engineer to design and inspect the foundation. The limiting of the liability works in two ways. The engineers design should be better by its very nature than a non engineered design, and the engineer is charging a substantial fee for the total package of his work and should be covered by some type of insurance. For this fee I feel he should be able to stand behind his design. I have to stand behind my work forever (10 years). Obviously reality is a little different than the scenerio that I have put forth here. Thanks for the advice.leigh
*Leigh,Since you are building on a former pond there are many unkowns. Your engineer is responsible for his calculations for the rest of his life. However he probably wants to limit lawsuits claim due to unkowns. You could probably still sue if there were defects in his calculations. The construction company I work for has about four pages of fine print on their subcontracts. Lawyers often advise clients that they would be potentially at risk by signing. But--the company I work for is ethically and morally right no one that is also ethically right have been harmed.
*Leigh,If you want engineering services, buy them. If you want insurance, buy it. Don't try to buy your engineers professional liability insurance.Considering the potentially huge costs to safely build over an old pond, your house might well be worth more than the engineers cap anyway.Mike,A construction company that's "ethically and morally right"? LOL.BCK
*bc,Just this morning I called up the electrical sub and pointed out a 7K math error in his favor. I sleep good at night knowing I am not cheating anyone.
*Mark,I've met many honest people, and it sounds like you're one of them. I'm less sure of companies in aggregate. My wife and I have both been involved in the construction industry and have dealt with hundreds of firms small to large. I'm sure there are some "ethically and morally right" ones out there, we just haven't found them yet.BCK
*bckelly1,I'd hate to live in your world.I don't deal with the unbethical ones so the ones I deal with are all honest and above board. Like attracts like, in this case.
*piffin,I'm almost certain we're walking the same globe. That's life.