Beam advice

[RicodJour]

Steve, if you want people to be a cheering section for you, well, asking structural questions on a construction newsgroup is not the way to go, particularly if you're not prepared to listen. You have not received a single useless reply yet.

As far as it being your house - no mortgage? The mortgage holder would be extremely upset to find out that you've made major structural modifications without pulling a permit. But even with no mortgage, you should be concerned as least as much as a bank would about not cutting corners on your own home.

I took the opportunity to cross post this reply. Since you've asked this question on both groups without crossposting (cross posting is not always a bad thing - it's bad only when it's to non-related groups), you are not allowing people to see the replies you've received and given. Partial information won't help your cause.

Remodeling _is_ building. If you modify the structure of your house you are required to pull a permit. Other factors will trigger the need for a permit, but a structural modification always requires a permit.

If you were in an area that didn't require permits - which, from your reply, you're not - you'd still be foolish to skip out on an engineer's review. Your picture shows more information, but still lacks critical information. Which way does the ceiling framing run? What are the required design loads? Are you in an earthquake or high wind zone? I could keep asking questions, but hopefully you've caught my drift. Only someone who has seen your house, inspected the current situation, and is familiar with you local code and area can design you a solution.

Beginners often mistake the strength of the beam as being the only factor in removing a wall. It's not - not by a long shot. The bearing area of the supports, designing connections to transmit loads other than gravity, adequacy of foundation supports, etc., are all critical. Simply picking a beam that can support a specific load is just a start.

You may have overestimated the cost and underestimated the value of an engineer in you situation? Have you called around to get an idea of the cost?

R

[marson]

hi again. you really ought to look into calling a company such as truss joist macmillan or weyerhauser and asking them to size one of their products. I have done this on a number of occasions, and i didn't always have a set of blueprints. a pencil sketch will do. i have found engineers that work for truss companies or beam companies to be very helpful and practical. an LVL, microlam, or parallam is more expensive, but will give you peace of mind that it isn't going to sag.

14' is a fairly long span for a homemade beam..

it is also true that there are span tables around for sawn beams, and you could fairly easily figure out your tributary loads and size your beam that way, if you have an aptitude for that sort of thing.. (do it like a professional engineer and overbuild it!)

As for hiring an independent engineer to design this for you, i wouldn't recommend it. I've gone this route and felt like the result was overbuilt--which I could have done without spending money on an engineer. you can't really blame them...they are liable if a beam sags or building collapses or whatever.

I used to work in a "non-coded" area. (technically you must follow codes, but they are not enforced). Kind of miss it in a way.

[Phil Scott]

Errr Steve? Rico is exactly correct and for some reason is showing you polite consideration... you do not deserve ..by a long shot.

Will you pay attention to Rico and thank him for his superb and accurate advice on these issues..... or will you just demonstrate your combination of ignorance and abuse.

ah yes... the latter. Impressive.

Phil Scott

[nicksanspam]

You doubt it will hold up a 5022 lb uniform load? Seems conservative, IMO. Concerned about torsional longitudinal stability again? How many pounds would you estimate Steve's beam would support?

My PE friend says Unistrut has several failure modes. It's stronger with the open side down, supporting a hanging load. Nuts to hold the sides together might help in that case. Short lengths with the open side up have a local buckling mode, with the upper edges developing waviness. I wonder how to predict that.

Nick

[Pat]

If you could reduce the span to 12 feet by leaving a short wall in place your 3 2X12's would probably work.

[RicodJour]

I'm thinking of a number, Nick. What's your estimate of what that number is? That is _exactly_ what you're asking. There are too many missing variables to make anything more than a wild assed guess. Precise calculations, or even yours, will not offset the missing information.

My PE friend... Please state for the record that you are not a civil engineer and have no business pretending you are one. Consider it a public service.

What does Unistrut have to do with the topic of this thread? You're not obsessing again, are you?

R

[jssm650]

While it is true that one would need to see your house in order to give any kind of idea as to what to use, and an engineer is not a bad idea, I have a couple of comments. First of all, why the half inch plywood. This is not going to add to the strength. The only reason plywood is added to headers and beams is to expand the width. (two 2x12=3in. and a

2x4 is 3 and half inches). Also, I have been building custom homes for many years and I can't think of any situation where three 2x12's weren't sufficient for a span of only 14ft, but it is always better to be safe than sorry when it comes to an investment such as your house.

[nicksanspam]

And your estimate is...?

Nonsense :-)

Nick

[Michael Daly]

This is exactly why you should not be taken seriously. You have your equations, but you haven't got a clue.

Mike

[RicodJour]

But he is a chipper fellow. It doesn't offset his tenuous grasp of logic and engineering - still, it must count for something.

Do you know that TV show NUMB3RS? Nick would be a great "guess" star. While he was running off half-cocked and making stupefying assumptions, the stars of the show could proceed to resolve things in a rational manner. Kind of a Point/Counterpoint thing.

R

[Goedjn]

I think that, if you're not willing to hire a pro to do the math for you, and given the level of understanding implied by your posting(s), you're foolish to be attempting this major a renovation by yourself.

That said, If this a single-story section and a gable-end, and you're expanding onto a porch, which is what it looks like, then you're PROBABLY ok with a built up glued and screwed beam of 3 or more 2x12s. Assuming that you post down properly through the floor and land on something solid underneath. This "you're ok" only applies if the surrounding structure looks like this:

If there's another floor above you, or this is a side wall, you should probably rebuild most of that wall and content yourself with a pair of wide doorways and a window.

Note that there's a very good chance that that masonry stack is holding up a beam in the ceiling and/or the ridgepole of the roof, depending on how old it is. Don't get too enamoured of the idea of taking it out until you know for sure what it's holding up.

You really need to open up a hole in the ceiling above to look at what that wall is holding up, and how the ceiling/roof structure is put together. and get pictures of what's underneath in the cellar/crawlspace.

My suggestion, If you're not going to do the sensible thing and hire a pro, is to leave the chimney in place, flank it with a pair of 4x6 posts, put another pair of 4x6 posts at the ends of the 14' opening, like so:

And then design around the chimney. It MIGHT be overkill, and it's not quite what you wanted to do, but an abundance of caution is a good response to working outside your area of competence.

--Goedjn

[nicksanspam]

You have my numbers. Where are your numbers? :-)

Nick

[RicodJour]

Nick, this is not a mental exercise. We're not playing with numbers because we're bored. It's a real guy's house, with a real question about the structure. With out real information about snow loads, earthquake, wind loading, all of that fun stuff you ignore, and which can _easily_ supercede any occupancy or dead load, the numbers are imaginary. They have no meaning. So what's the point in _guessing_ at a solution?

The fact is, you really don't care whether it's a real situation of not

- a real house or not. You see no difference because your first love is juggling numbers. To each, his own. But please don't go selling your "solution" as anything other than a mental exercise.

R

[Michael Daly]

Your numbers are useless in the absence of load information and details on the beam support. There are two sides to the general problem of building a structure, P and R - loads and resistance. You are focussing on only one.

Mike

[Michael Daly]

PE in what? - Electrical? Chemical? Transportation? If he isn't a structural engineer, he isn't likely to know what I've pointed out to you.

Show him the Unistrut manual and ask him to explain the column on the extreme right that lists load reduction factors. Let us know what he has to say.

Plate and shell theory. FEA would be easier.

Mike

[nicksanspam]

This is Beams 101. I'm surprised anyone would argue about it, unless they don't understand it or just love to argue :-)

And engineering is done with numbers. Or perhaps feeble arm-waving, for the numerically-illiterate :-)

The USENET bestiary also includes those who say "We can't see it from here" and "You must hire an engineer" and "WATCH OUT!!! WHAT YOU ARE DOING COULD BE DANGEROUS!!!" :-)

The OP described a beam and asked if it would be strong enough.

Estimating its strength is a reasonable first step.

Nick

[nicksanspam]

Structural engineering, which he also teaches and writes books about. He's the lead engineer on a $20 million building now. He uses lots of Unistrut in his work.

Local buckling.

We talked about that ("page 61") and I asked where the curve came from.

He said Unistrut has several failure modes. I guessed the curve came from the main twisting one with the open side up, vs the local buckling one for short lengths, with a safety factor. Where do you think it came from?

Perhaps you can answer this question: "Exactly how much perturbation is needed to cause torsional longitudinal failure as a function of load?" You might say "Exactly zero, at full load," or "Exactly zero, at the derated load on page 61," but neither of us would believe that :-)

Then again, from a quantum-mechanical point of view, there is an infinitestimal but finite probability that every molecule in a 10' strut will suddenly decide to be somewhere else for an instant...

Nick

[Edwin Pawlowski]

To be a PE, don't you have to have knowledge of various fields?

[nicksanspam]

Yes, esp after the FIT exam, with questions about dam design, crystallography, electronic controls, and so on. In PA, an electrical PE can legally design bridges and skyscrapers. And pediatricians can do brain surgery...

Nick

[RicodJour]

What's your point? That there are stupid regulations with lots of loopholes in existence?

Or are you suggesting that since you don't know anything about the specific design requirements of the original question, you can concentrate on Beam Theory 101 to "offset" the lack of information?

Gee, my car's not starting, but I don't know anything about engines. Let me make sure the tires are at the right pressure...

R