Hi,
I am building a large storage shed that has a loft area above it. The shed is stick built, with 14′ high 2×8 walls. The building size is 48′ x 104′ plus 12″ eaves on the gable and rake ends. The roof system is trusses and the entire shed has room in attic trusses with a 2×12 bottom chord. Ground snow load in my area is 30#. The roof pitch is 8/12.
According to the truss designer, the live load and dead load on the headers is 1925# per linear foot.
The garage door openings are as followw:
(2) 12′ high x 12′ wide
(1) 12′ high x 16′ wide
The contractor elected to use multiply LVLs for the garage door headers. The headers extend past the rough opening 2′ on each end for additional shear strength.
For the 12′ wide openings, he used two 1.75″ x 14″ lvls.
For the 16′ wide opening, he used three 1.75″ x 16.5″ lvls.
I double and triple checked the measurement on this, and it is 16.5″. I’m not sure who makes a 16.5″ tall lvl, as I don’t see it shown in any charts. To me these seem small, and I don’t like the fact that the headers don’t fill the entire depth of the 2×8 stud wall. The LVLS were installed to the outside edge of the framing, so for the 12′ wide openings, I still have room in the framed openings to install two additional 1.75″ x 14″ lvls. For the wider 16′ opening I have the depth to accomodate one additional lvl.
According to information I can find online (if I interpret charts correctly) it looks like I need (3)1.75″x14″ lvls for the 12′ opening and (4)1.75″x16″ lvls for the 16′ opening. If that’s the case, would you also fill the entire width of the opening with a structural element even when it’s not needed, i.e. (4)1.75×14″ lvls for the 12′ opening.
Replies
There's absolutely no reason to fill the entire depth of the wall studs with headers.
Off the top of my head, the LVL sized & plies that you say have been installed are about what I would expect to see here. But no way could I say for sure if they're adequate for your structure without knowing your local codes, loading requirements, and seeing a design of the attic truss.
Where did you come up with that 2343 numer that you highlighted in the span chart?
The LVL that's 16.5" tall is probably a wet 16" deep LVL. It will shrink a bit given time to dry out.
Over our 16-foot garage door there were originally two 2x14 pieces of lumber (13 inch actual height). These were sagging about an inch in the middle. When we resided I replaced those with two microlams that I think were supposedly 12 7/8". They sag maybe 1/8" and I compensated for that with wedges.
This is in Minnesota, with substantial snow load possible (though no official loft overhead).
Based on this personal experience three 16.5" LVLs would be way overkill for just a roof. What's unknown is the design parameters for your "loft".
worse than worthless
This type of anecdotal advice is not only worthless to post, but (IMO) crosses the threshold into being downright dangerous.
Why are you aksing this question of the forum?
This accessory structure your builidng is clearly over 200 sq. ft. I assume a permit was required to build it. So what does your approved set of building plans call for at this structural header condition?
BTW, why would extending past the rough opening by 2' give you additional shear strength?
Not necessarly
Have seen you make that remark several times now, and although that may be true for the area you live in, it is not the case everywhere.
I have built plenty of garages, large sheds (which this shed is a monster of a "shed") and all Im required to show for permitting purposes is a sketch showing that the proposed structure is abiding all set back restrictions and heigth restrictions when they apply.
So, not everyone needs what you say is absolute basic to build while permitted.
Where's that?
I have stated in this forum (and others) that most juridictions in the U.S. have adopted the IRC and that most accessory (including shops, garages, and shed) stuctures over 200 sq. ft fall under the perview of the IRC. You can infer by that statement that it does not mean all juridictions. Therefore, it's hardly a claim of absolute.
May I ask in what town or city you primarily conduct your business, Mark?
Does that mean Hamilton County, TN?
Mark
near Nashville? I'll meet you for a beer in a few weeks.
shoot yeah man, im a short drive away from Nashville.
Mark
right now am in Spokane, then headed across the state to visit crazylegs and family. Portland and N. California then maybe head back east.......
there's no real plan, but eventually will be in Nashville on the return to Toledo. Itinery I've got, timing is a bit in Question. I'm trying to monitor some things, but the information hi-way is so so. So when close to the Mississippi, I'll try to come back here and find you.
I sneak in here as time and connection permit to delete some British kitchen ads. Keep up the good fight.
great. hope we can make it happen.
You may want to re-think your permit responsibilities
mark122 wrote:
Chattavegas, TN. We are governed by the IRC, previous comment still applies.
It applies to you if you're buidling in Hamilton County TN. They adopted the 2012 IRC July 1, 2013. According to the Hamiltion County website a building permit is required for any new, alteration, addition, or repair which is valued at $100 or more. Those building permit requirements are stricter than ours here in Northern VA. BTW, the City of Chatanoogs adopted IRC 2012 on May 29, 2012.
You may have been able to get a permit with your napkin sketch in the past. However that doesn't negate your responsibility to abide by the IRC for your plan review & field inspections if you now operate in the TN jurisdictions indicated above and your project requires a building permit. Does that mean that every plan reviewer or field inspector will enforce the IRC in those juridictions? No. But it means they have the authority (by statute) to do so.
What? you are telling me you know better than I do about what the process is like in my city? You are out of your mind man.
You can attempt to compensate for what ever you feel lacking in by attempting to dazzel with elocuence and lecture but you are mistaken if you think anyone is taking that bait.
In plenty of occasions you take what someone says and misconstrude it to attempt to make a point. This discusion began when you demeeningly told a guy
" This accessory structure your builidng is clearly over 200 sq. ft. I assume a permit was required to build it. So what does your approved set of building plans call for at this structural header condition? "
The guy was simply asking for a second opinion on the sizing of some headers. To him, they seemed undersized so he was asking guys who do that kind of thing for a living to give him some imput based on their experience.
to that comment i said,
" I have built plenty of garages, large sheds (which this shed is a monster of a "shed") and all Im required to show for permitting purposes is a sketch showing that the proposed structure is abiding all set back restrictions and heigth restrictions when they apply."
Be competent in what you do, be confident in what you do...but for goodness sake man, dont presume to know more about what I as a General Contractor do, dont do, or should do.
Apparently I do.
I'm telling you what the permit and inspection requirements are in Hamilton County and the City of Chattanooga. It's public information--man. You may not like those rules* or abide by them. However, that doesn't change their application one iota.
BTW, unless you're a professional engineer, you don't size beams for a living. You size beams according to prescriptive code or manufacturer's specifications. All that information is available publicaly to anyone that's not too lazy to look it up. The gentlemen that has a question about his beam has this information at his disposal without soliciting from this forum. If he can't reasonalby find it, then it probably means he needs the services of an engineer. He doesn't need to ask non-engineers (including myself) what he should do or for second opinions. It's unneccesary, futile, and potentially dangerous. Doing so would be like going online to get a second opinion about a medical condition that requires surgery. Who knows? Maybe you do that.
* I have read disparaging remarks made by you in other threads about the IRC. I don't personally care about the IRC myself, but professionally I respect the authority my building juristication has by adopting them. If you're a professional builder and they apply to your project, then you should as well. That's a fact; not an opinion.
ok
More information
Boss & Others:
See attached diagram for my truss layout and truss design.
To clarify questions asked by others:
1. Yes a permit was needed and taken out. However, since the building was permitted as an agricultural building it is not subject to the same engineering requirements that might be required of a commercial structure. Even if it were a commercial structure, my township is extremely lax on inspections and oversight. that being said, I am investing a significant sum of money in this building. I do not want to, nor am I planning to, take any shortcuts. Although the building wasn't engineered, I have spent countless nights doing research, reviewing plans of similar buildings in my area, checking load charts, etc. I am confident that the building will be significantly better than code. When prescriptive coad is available, I typically exceeded it.
2. The garage door headers will have a significantly higher load than an average garage. The doors are not located on a gable end, so they are bearing the full load of the exterior wall. In addition to the snow loads I have (ground snow 30#), the trusses are also bearing a residential floor load for the attic area (treated as bedroom loading), and the roof trusses are significant. The floor plan is entirely open. I have no intermediate bearing walls and no support posts. The room in attic trusses are spanning 48' minus the thickness of the 2x8 stud walls. Since the trusses are also capped (8/12 pitch trusses on a 48' span are TALL) I have additional roof dead load.
3. I don't want to fill the full header depth if I don't need to. I would prefer 1-2" of rigid foam sandwiched in there if possible.
4. Boss, I used the highlighted number as if I read the chart correctly, that was the next combination of LVL size and number of plies that exceeded the 1925# per foot uniform load that my building exerts.
5. The idea of the two foot overhangs of the headers is that the header is blocked and fastened into more studs and more sheathing. See APA recommendations for narrow walls. There is a very heavy fastener schedule that must be followed, especially since I have multiple wide garage doors. In order to increase shear, I have kept a minimum distance of 6' for doors and windows from all building corners, and have 6' between the garage doors. Additionally, the building will be sheathed with plywood on the exterior and interior walls.
6. If you review my attachments, the doghouse dormers align with the garage door openings. Since the roof structure is trusses, the small dormers have a 6' wide area that is hand framed. The larger opening has a 10' wide area that is hand framed. The thought process is that I would combine the point loads of the dormers with the multiply jack and king studs at the garage door openings. (Trying to increase the areas of insulation)
Thanks for everyone's thoughts and assistance.
What code is that?
rocket190 wrote:
Boss & Others:
I am confident that the building will be significantly better than code.
Your bullet item #1 containes statments that are very questionable. in particular:
1.What is the applicable building code that your applying to your "agricultural building" and intending to weigh your building confidence against?
2. If your township has issued a permit and requires inspections (whether they are "lax" or not) , then what buidling codes are they intending to inspect under?
The reaction at either end of the truss is 3,850#. Divide that by 2 and you have 1925 PLF.
In the LVL span chart you linked to, the capacity of the LVLs where you highlighted them show a capacity in PLF of over 2,300#. So your LVLs are fine.
A couple of other comments - Wherever you have a double or triple truss around those openings you need to make sure there are studs under the trusses.
Make sure you have planned out your stairs carefully. You can't cut out any part of the truss BC for stairs later on without a ton of hassles.
IMHO the BC of the attic truss is too long. a 20' span on a 2x12 BC will likely have quite a bit of bounce in it. No way would I have ever sent out a truss design like that.
The truss company will likely tell you it's fine, their engineer will seal it, etc. And I'm sure it's technically O.K. My objection is based on experience. I don't like pushing the limits of floor members.
To those of you getting in a pissing contest over whether the building had to be engineered and permitted - Many of the areas where I work in Illinois have no building codes and no building departments. Others are all over the map in what they require.
So applying what you see in your corner of the world to everyone else doesn't work.
Boss, thanks for the helpful information. I do have multiple studs under all the multiply trusses. I have three studs under the triple ply trusses at the six foot openings and four studs at the 10 foot opening. I also have a planned 6' wide stair opening. With an l shaped stairs I can meet all the codes for landing sizes and riser/tread dimensions, plus my stairs will be almost 6' wide which will make bit easy to get up and down.
regarding the bottom chord, I had concerns about that. I reviewed a competing truss design that offered a 24' wide room that had a hybrid truss that incorporated an open web floor truss as the bottom chord. Ultimately I decided to go with a local manufacturer that was well regarded. Do u worry about the l/360 deflection? The bottom member is machine graded structural syp, but it's still approaching the limit of span. I'm a slender guy, so I don't notice much bouncing. I do feel some deflection in the subfloor (3/4" advantec) but it's not too bad. For insulation value and to reduce bounciness I was considering strapping the bottom chord with 2x4s laid flat. Alternatively, I could add strongbacks. What do you think about those options?
another alternative would be to add additional support at the mid span. How would a 12' 2x10 screwed and glued at the midpoint reduce bounciness?
thanks again for your comments.
Boss, would you have suggested a narrower room or a different size or type of bottom chord?
"would you have suggested a
"would you have suggested a narrower room or a different size or type of bottom chord?"
Yup. On floor members I like an 18-to-one ratio of length-to-depth. i.e. a one foot deep floor member shouldn't span more than 18 feet. A 2x12 would max out somewhere around 17' 3".
That's only my personal preference, based on some bad experiences with floor design using L/360.
I know I'm on the conservative side on floor design. Some people appreciate it. Others get pissed off.
I can tell you I have't designed a floor for anyone in the past ~15 years that was unhappy with the preformance.
The L/360 number isn't what I watch for. Deflection and vibration are 2 different things, and are only loosely related.
Adding lumber to the sides of the BC won't likely do anything. Strapping may make a litttle difference. But I doubt it would do a whole lot.
Many years back I did a thread on floor vibration, where I tried to explain what I've learned and why I'm conservative. If you want to read it, here ya go:
http://forums.finehomebuilding.com/breaktime/general-discussion/floor-vibration
That's B.S.
BossHog wrote:
To those of you getting in a pissing contest over whether the building had to be engineered and permitted - Many of the areas where I work in Illinois have no building codes and no building departments. Others are all over the map in what they require.
So applying what you see in your corner of the world to everyone else doesn't work.
Doesn't matter if your local has no building codes or building department(s). Professional, quality building is not a matter of catering to the lowest common denominator. If you're on this site, then you have access to a wealth of residentail building knowledge and insight. That includes using and understanding the IRC whether it's adopted in your area-- or not. These codes and presciptive building methods have been developed by some of the best engineers and builders in the world while being honed over many decades as a result of incorporting the 3 legacy codes (BOCA, UBC, & the SBC. The IRC works. Does it work for all situations? Hell no. That's where other design professionals (including (most commonly P.E.'s) may play an integral part in your project. With today's connectivity and technology there is no excuse not to utilitize the IRCand the services of design professionals (if needed) while building ANY project in ANY part of the world.
I am not sure what's questionable about what I said. Wisconsin has mostly homegrown codes. The reidential code is the Wisconsin Uniform Dwelling code. This isn't a residence, so not applicable. The commercial building code is loosely based on the IBC. Like many things agricultural, this building is exempt from standard codes. My township does not have a zoning department, so it defers to county zoning. County Zoning would normally apply, but ag buildings are exempt. When I asked my building inspector (also the electrical inspector, dog catcher, etc) when he needed to inspect, he said "I'll stop by sometime when you're done."
I will reiterate that I'm not looking to cut any corners. How many stick framed buildings do you see that are constructed with 2x8s, sheathed on both sides of the wall with Plywood, have roof sheathed with 5/8" plywood. I'm not lazy or stupid. I've read a lot of prescriptive code. Once a wall is taller than 10' there is no prescriptive code applicable. Most buildings are fairly unique and prescriptive code can only cover so much.
that why we hire engineers
rocket190 wrote:
Most buildings are fairly unique and prescriptive code can only cover so much.
That's exactly right. The IRC and other code reference books are not meant to be "how to" books on building. Where the codes presciptive requirments end is where professional engineering takes over. That's why there are students that go to engineering school and become professional engineers--to help folks like you. Folks who want to build knowledgably, confidently, and safely where prescriptive code is unapplicable. However, these professionals charge for their services in order to maintain a viable business model. In my opinion, you're attempting to circumvent this aspect (i.e. time & cost) of your construction project. I don't know why. Perhaps you feel you cannot afford their service or don't trust engineers in general. What I do know is that unless you get advice from someone on this forum that is a professional engineer and becomes the engineer of record for your project, then any structural advice which goes beyond explanations of prescriptive code, supplier specs, or general structural concepts is worthless. In fact, I've said it before and I will say it again: Not only is it worthless, but it is perhaps dangerous.
That opinion applies to Boss's adivce as well. He seems like a good natured fellow with some background in pre-fab framing material supply that genuinely wants to help you out for free. That's great. But unless he has the creditionals to back up his advice then, he too, (IMO) is wasting his time--- as well as yours.
Just FYI - I've been in the truss business since 1984. Started out in the plant and worked my way up through the ranks.
I learned how to do truss and beam design mostly by hand. As the industry and computers evolved I sort of "grew up with the industry". I learned from some of the best truss engineers out there and have been to many conferences.
I've been writing about trusses and related topics here on BT since the mid 1990s. I've also been hired by framers to help set the trusses I've designed. Built my own house and helped on many others. So I have a unique mix of technical and practical experience.
So I damn well do know what I'm talking about.
Legally, no you don't.
You've beat everything around the bush, but it sounds like you don't have an engineering degree. Sorry, it doesn't matter what you think you're talking about. If fact, I doubt you've been the engineer of record for any project while working with any associate or company. Legally, your engineering prowess ends at prescriptive code for any municiple plan reviewer.
I know more about trusses and truss design than most engineers. Never claimed to be an engineer.
Just making the point that I do know what I'm talking about.
Deadnuts,
You seemed to have glossed over the fact that I am asking for a second opinion. My builder and material supplier have both told me the LVLs spec'd are adequate for the load. Since I don't know how they came to that conclusion I asked other knowledgable builders for advice.
I work in the building trades and deal often with engineers. I respect their education and services, but let's face it....there are bad engineers just like there are bad builders and bad doctors. I have seen some really stupid things over the years that engineers have stamped that do not work or are not practical in the field. Since the trusses were pre-engineered the only thing left to design were the walls and foundation. In Wisconsin we are lucky to have zero seismic reaction and relatively low wind speed values.
In my building career I have seen thousands of plans so I do have a basis for what is acceptable design. Last year I worked on the demolition of a commercial building (stamped plans) that failed during a f2 tornado. The building stayed in tact, but was racked to the point that it had to come down. This building was 16' sidewalls x 60'wide x 140 long. Wall construction was triple 2x6 at ten foot intervals, common trusses at 10' intervals, and 2x4 gurts/purlins at 32" o.c. Spacing. Ribbed steel roofing and siding.
My building has lower sidewalls, 2x8 framing on standard intervals, roof trusses on 24" spacing, 5/8" plywood decking, 1/2 plywood interior and exterior sheathing, 3/4" interior sheathing on my wall with the garage doors, AND ribbed steel siding on the interior and exterior. I'd be willing to bet the shear value of my walls will far exceed code.
Then ask an engineer. If you need surgery, do you get a second opinion from your builder, your grocer, or your mechanic? No; you get it from another doctor.
BTW, the reason you probably don't know how other engineers came to their conclusion9s) is because you don't have enough knowledge to ask the right question or understand the answers. In other words, you don't have the formal training (degree) they do. If you did, then you would solve your concerns yourself and not have asked the original quesiton posted here on this forum.
If the shoe fits....
Rocket-
I don't make it a habit of sugar coating my opinions or advice. If your imaginary exchange suites your fragile ego better than reality, then apply it. The net result is the same as I am just trying to help you.
If your current question is: Since I am too lazy to look up a professional engineering firm that may be able to help me where I live, is anyone here so inclined to do that work for me and provide possible leads? My answer: Sure thing.
Here you go: http://civil-engineers.regionaldirectory.us/wisconsin.htm.
I imagine somone on this list of 100 or so professional engineering outfits can help you (or knows someone who will help you) in your neck of the woods. I know the engineer I work with is licensed in VA and MD. I doubt he will be able to help you in Wisconsin as professional reciprosity is not a given across the U.S. However, if you hit a wall with this list, then P.M. me and I will send you his contact info and you can see if he'll help you.
BTW: You say you'll put your "money on the fact that 50% of them [engineers] graduated in the bottom of their class". Whooh!--way to throw down the guantlet dude. Since half of them will be in the upper half of their class and the other half will be in the lower half by statistical definition, that doesn't constitute much of a bet. You wouldn't have an edge on anyone at the horse track with that kind of dull betting insight. Then again maybe you'd only put your money down when it's a one horse race... and coming up lame still counts as a win. Good luck finding those bets.
Deadnuts,
i'll never understand what motivates a person like you. I've had the pleasure of meeting many successful and engaging people in my lifetime and none of them would spend so much time attempting to demean people on a HELP forum. There are several engineering related forums where engineers ask other engineers for help (gasp!!)
Also, you clearly missed the sarcasm in my 50% bet, but that's okay, I didn't expect you to get it.
You can go back to being a troll and I'll go back to making money. Lot's of it.
here's your free help...
This is general discussion forum, not a "HELP" forum. But I can understand why you need quite a bit of the later.
BTW, since you had already been demeaning the value of engineers, your "50% bet" comment hardly constituted sarcasm. Maybe you should visit some English language "HELP" sites as well. They might even be free*.
* That's what you've really been looking for all along.
You can get over yourself about any time now.
rocket190 wrote:
Dead,
your disparaging remarks aren't very helpful. So far you have inferred that I'm lazy, unintelligent, frugal, and of the lowest common denominator. I am none of those things. There are many very knowledgeable and generous people on these forums. How am I to know there isn't an engineer member of the forum that could double check the beam size?
I am a degreed and licensed professional Engineer. Very few of us in that club offer free engineering advice on forums, due to the legal issues. I don't need the liability issues that would come with giving quick advice with out a full review of the plans and specifications involved. Plus, I am rarely licensed in the states from which the questions come, which could cause issues of doing engineering without a license. Both of these are grounds for revocation of an Engineering license. If they censure and engineer in one state it is immediately effective in all other states. I invested a great deal of time, money and effort to get my degree and license. I won't risk it giving free advice. Nore will most other qualified engineers. Not to say categorically that an engineer won't respond, but the probability of a qualified engineer answereing is very low.
[quote =rocket190]
As an aside, going to college and earning an engineering degree isn't a cure all. Engineers can and do make plenty of mistakes. And for every graduating class of engineers and doctors, I'll put money on the fact that 50% of them graduated in the bottom half of their class. I can think of many fully engineered buildings or structures that failed spectacularly. I can think of many structures hundreds or thousands of years old that have stood the test of time. Were any of these buildings designed by Harvard engineers? What do you suppose was the formal training of the person who designed pyramids or the great Cathedrals that are still standing. I'll bet it was practical knowledge, apprenticeship under experienced builders, and they study of prior structural failures that allowed them to reach their conclusions. The Greeks and Romans may be an exception as they had some amazing mathematicians.
There are lots of buildings that failed you don't see. And, most of those structures that survived are extremely over designed. Any one can build a structure that will hold up if they put big enough parts in it. You can quickly solve your problem of the sizing of the members over your doors: Just add more. All you have to do is throw money at them.
You could have consulted an Engineer in the beginning, assured the building that met the requirements you have for it, and minimized the amount of materials used. Good engineering is what assures you spend the least amount on construction possible.
You elected to not go that way, and now have a question midway through construction. At this point it will probably be most eonomical to add LVLs and over build if you have doubts. It is typically more expensive to bring an Engineer in after the boards are in the air, because thy now have to review not just the design, but every part of the construction, and back engineer the solution.
As to half of the Engineers graduating in the bottom of their class: Engineering licensure requires three things;
1.) An Accredication Board for Engineering and Technology, accredited degree from an American university, or degree from a foreign university that meets the ABET requirements.
2.) Passage of an 8-hour exam in Engineering Fundamentals. The passage rate on that exam is about 60%. You can take this exam after you acheive Junior status in college. (At the Junior year in most universities, over 50% of freshman who thought they would study engineering have dropped out or are studying something else).
3.) Passage of a second 8-hour test after you get a minimum of four years of pregressively more responsible engineering experience under the direction of a Licensed Prefessional Engineer. Again the pass rate is around 60%.
This tends to eliminate the Engineering graduates in the bottom half of the class from licensure, as roughly only 36% of those taking the two exams pass the two combined.