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19 foot header

dbanes's picture

I'm marginally sure 3 2x12's would carry 19 or 20 feet, right? considering that is right,  should I attempt to create a crown in this sandwich in the process of marrying it all up? I'm thinking I could aclimatize my materials on the floor, with a hunk of 1x4 in the center before the work starts and once its crowned, nail those bad boys together, and maybe some weighting?Any body been here before?

Scribe once, cut once!

Scribe once, cut once!

(post #96302, reply #1 of 25)

Be prepared for lots of advice to consult a pro.

I will add to it. 3 2x12's will easily span 19 feet. If they are used as floor joists with no additional load. Past that point it gets slippery.

What kind of loads are you looking at? Have you considered LVL's, Glulams, flitch beams etc.?

 


Jon Blakemore

 

Jon Blakemore

RappahannockINC.com

Fredericksburg, VA

(post #96302, reply #3 of 25)

As Jon says, what are you loading on the sandwich? The title of your post says header, so I assume this is not a floor joist situation. I recently had a beam sized to span 17 feet. It will carriy ceiling joists with attic above used for light storage, no direct bearing of any roof loads. The smallest beam allowable is a 6x14 DF#1, with glulams and LVLs going up from there. In a header situation under a second story with a slate roof at 14:12 you could easily need way way more than 3 2x12 to span an opening. Engineer time, in my opinion.

(post #96302, reply #4 of 25)

I'm getting some help from your post,The load is a single story roof 4/12 pitch fiber-glass shingle ( the bracing comes down on this member)  also carrying ceiling joists 12' long on both sides...What about  the crown? I see so many 16' garage door openings with a bad sag ,I want to have a good long -lasting presentable ceiling...(this is all for the H-O who is leery of the cost of a beam of "engineered wood")(you can lead a horse...)


Scribe once, cut once!


Edited 10/5/2004 7:34 pm ET by mapache

Scribe once, cut once!

(post #96302, reply #7 of 25)

Mapache, those headers are sagging because they are unable to carry the load. I doubt your idea will work. Building in a camber will not work either...it'll just straighten it self out when you release, unless you go to extraordinary efforts to buttress the ends.


Don't be cheap...buy the micros...they work!


I installed two 1 3/4" micros with a 2x12 today to carry the garage that I'm working on. It has a room built into the trusses.


blue


 


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"...

keep looking for customers who want to hire  YOU.. all the rest are looking for commodities.. are you  a commodity ?... if you get sucked into "free estimates" and  "soliciting bids"... then you are a commodity... if your operation is set up to compete as a commodity, then have at it..... but be prepared to keep your margins low and your overhead  high...."

From the best of TauntonU.

(post #96302, reply #8 of 25)

To give you some ideas, here is some info from Trus Joist's Specifier's Guide for LVL.


For a house width of 30 feet, single story, only the roof load (and whatever DL is coming from ceiling), 18'3" R.O., non snow area, roof loading 20 psf dead, 15 psf live, use a 3-ply (5-1/4") LVL at 11-7/8 depth.

Gene Davis, Davis Housewrights, Inc., Lake Placid, NY

 

 

(post #96302, reply #9 of 25)

> also carrying ceiling joists 12' long on both sides...


So you have 6 ft. of tributary ceiling load on each side, 12 ft. total.  Live load for an accessible attic at 10 psf, and a ballpark ceiling dead load of at least 8 psf puts you well over 200 pounds per linear foot on a beam that's only good for 140.  And that's not even looking at the roof load.  So the answer is that the 2x12's are out, you need to get something better designed for this. 


How much room do you have in the attic above this ceiling?  Depth is a godsend in beam and truss design, the higher you can go the less material you need to put into it.  I think you're talking about a remodeling job, so getting the beam into the attic may be a problem.  Perhaps it would be good to go with some sort of modular steel truss design that can be taken up there in pieces and bolted together. 


 


-- J.S.


 

 

 

-- J.S.

 

(post #96302, reply #10 of 25)

"The load is a single story roof 4/12 pitch fiber-glass shingle ( the bracing comes down on this member) also carrying ceiling joists 12' long on both sides."

What BRACING are you talking about.

You either have a roof load and a ceiling joist on ONE side or you have ceiling joist on both sides.

BUT NOT BOTH!

That is for a simple gable end ranch. On if this was an outside wall and then add addition added on or some something simlar then you have a lot different loads.

. William the Geezer, the sequel to Billy the Kid - Shoe

(post #96302, reply #11 of 25)

Bill I think he uses the term bracing instead of rafters.


blue


If you want to read a fancy personal signature...  go read someone else's post.

"...

keep looking for customers who want to hire  YOU.. all the rest are looking for commodities.. are you  a commodity ?... if you get sucked into "free estimates" and  "soliciting bids"... then you are a commodity... if your operation is set up to compete as a commodity, then have at it..... but be prepared to keep your margins low and your overhead  high...."

From the best of TauntonU.

(post #96302, reply #22 of 25)

Roof cross-braces from rafters to the load bearing center wall...And yes ceiling joists toed up from either outside wall on the bearing wall...


Scribe once, cut once!


Edited 10/6/2004 3:59 pm ET by mapache

Scribe once, cut once!

(post #96302, reply #15 of 25)

Your header is gauranteed to sag, almost of its own weight, and you are ading the ceiling and roof loads to it.

I'm ballparking minimum 2-2x18 LVL but that might be light. I would go to the supplier to engineer and price it for you.

A HO who wants the cheapest way out wants the LVLs instead of failure because doing it again is very expensive.

The only other way I can think of to handle this creatively is to build a box beam, but then you are paying for an engineer and lots of labor which will cost more than the free engineerinbg form LVL people and little labor

 

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Oh Well,

We did the best we could...

(post #96302, reply #20 of 25)

...(this is all for the H-O who is leery of the cost of a beam of "engineered wood")(you can lead a horse...)


 


Warning sign right there.  Not the place to cut corners, IMO.


 


 


"Those who are citizens of God's kingdom are best equipped to be citizens of the kingdom of man"  -- St. Augustine

 

 

 

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I know this is an old thread, (post #96302, reply #24 of 25)

I know this is an old thread, but how big was your beam for that 17'? I have the same project I'm wanting to do to open up my kitchen and living room. Attic above with no storage in that section, just ceiling joists and maybe walking around from time to time to work on something if I need to.

(post #96302, reply #2 of 25)

everyone here will say "call an engineer"    but what he/she and everyone else will want to know is... what's it hold'n up?...   most guys on here know how to size headers and most people just "build em big"  but in this age of lawyers you about have to cover your butt...  i just spent 20k on engineer'n for the guy to tell me yeah the way u were plan'n to do it fine...   i'm kinda like... do i need insurance or an engineer?


 


p

(post #96302, reply #19 of 25)

You're confusing protecting your customers from harm (i.e. by hiring an engineer) versus compensating the victims after you've f*cked up (i.e. insurance).  Commonsense from years of building is of inestimable value, but it doesn't make you a structural engineer. 


All good professionals, engineers and tradespeople/builders alike, share one thing in common:  they understand the limits of what they know, and they don't confuse it with what they "suspect" or what "looks right". 


Find a good engineer and they'll charge you a heck of a lot less to check what you're doing than to draw it all out in laborious detail.  Remember- it's their neck on the line, so they're going to want to know that you'll be competent in installing what they tell you to and not take any shortcuts.

(post #96302, reply #5 of 25)

I just had an lvl spec'd for a 16' garage opening...carrying the second floor(40/10) and roof (30/10/10). 3 1/2 X 18" X 22' long (has to span into adjoining joist bays to comply with narrow wall bracing code). It is one big heavy dude and $350 to boot.


Jim

(post #96302, reply #6 of 25)

It depends how much load there is on the beam.  We can run some rough numbers:


2x12's have a section modulus of 31.641 cubic inches.  Section modulus is linear w.r.t. width, so three of them combined would give us S = 94.923 cubic inches.  If we're using #2 Doug fir, the maximum extreme fiber bending stress is Fb = 900 psi.


The maximum bending moment the beam can hold is M = S x Fb, so M = 94.923 in^3 x 900 lb/in^2 = 85,431 inch-pounds.  Converting to foot-pounds, M = 7119 ft-lbs.


The distributed load that puts that much bending moment on the beam is w = (8M)/(L^2), where L is the span, 20 feet.


w = (8 x 7119 ft-lbs)/(20 x 20 ft^2) = 142.38 lbs/ft.


It's that square of the span that really drags things down.  140 pounds per foot isn't a whole lot.  If this is on the ground floor of a two story house, the odds are just about nil that it'll be adequate.  If it's a door in the gable end of a garage, it could turn out to be OK. 


So, do a ballpark figure on your actual load.  If it's much more than 140 lb/ft., you'll have to give up on the 2x12's and get an engineer to design something stronger.  If it's close, you'll need to get a real engineer -- not just a guy who read a book once -- to run these numbers for real.


 


-- J.S.


 

 

 

-- J.S.

 

(post #96302, reply #12 of 25)

What does your plans/prints call for?  A good set of plans should spell it out for you.  If your plans don't give you the specks you should complain to the designer,  he sold you incomplete plans and is cheating you. 

(post #96302, reply #18 of 25)

Wishful thinking Fredsmart.


We just finished a large custom that required at least 30 clarifications and re-engineering of bearing points that were missed by the Architects, lumber suppliers and truss engineers. Some were major glaring omissions. Of course, in the field, we have to have something to hold up one end of a girder that is carrying 10000 pounds or more! We had to put in a 3.5" X 18" micro that was only 38 span in one section.


All plans and specs aren't always top shelf. Dimensions were missing all over the plans.


We smartened up on the next one. We started reviewing the plans 3 wks in advance...sent them back...sent them back....today, there were still items missing that I found. It's frustrating...but that's our life.


blue


If you want to read a fancy personal signature...  go read someone else's post.

"...

keep looking for customers who want to hire  YOU.. all the rest are looking for commodities.. are you  a commodity ?... if you get sucked into "free estimates" and  "soliciting bids"... then you are a commodity... if your operation is set up to compete as a commodity, then have at it..... but be prepared to keep your margins low and your overhead  high...."

From the best of TauntonU.

(post #96302, reply #23 of 25)

Thanks to all, I found what I need here as always before, It's great to have this forum...Keep it up FHB...!

Scribe once, cut once!

Scribe once, cut once!

(post #96302, reply #13 of 25)

IMHO, 2X12s spanning 19' won't really carry anything. They're even too far to use for floor joists.

I'd say you're looking at something like a 2 ply 16 or 18" LVL, depending on the actual load on the beam.

Check with a lumberyard about what's required in your area. They should have the resources to come up with the correct beam.

But don't be conned into putting in an inadequate beam by tightwad HOs. It could come back to bite ya on the butt.



Life is not a problem to be solved, but a gift to enjoy.

(post #96302, reply #14 of 25)

Most buliding suppliers have people that will spec this for you at no cost.  Consult your supplier.  May as well have som estamp of approvial.


 

(post #96302, reply #16 of 25)

Just ran into a similar situation with a 20 foot span and the engineer called for a 3 ply 16" lvl.  I guarantee it will not sag after testing it out.

(post #96302, reply #17 of 25)

There seems to be a concerted effort by some manufacturers and code writers to reduce the need for some basic engineering for builders and designers.


Your dilemma is a good example:  Boise Cascade, one of the manufacturers of engineered lumber and beams will provide you, free of charge, with a CD that will enable you to develop specs for load bearing engineered components.


Since the designs are already developed by licensed engineers, you can use the software to solve for your particular needs and, if you do the work correctly and print out the supporting documents, building inspectors have no choice but to accept the results.


I have a new building inspector in my area who is a complete horses' arse, who backed down on a recent modification I did on a basement garage to provide a wider span for an 18' garage door and eliminate a center portal wall and a center post within the garage (the original plan called for two 8' garage doors).


The solution derived from BC's CD enabled me to install two laminated beams instead of one and put 650 series I-joists on 12" centers.  It cost the customer a few $'s more, but they will have a free-span open garage which they preferred.


There is a bit of a learning curve on the software, but it's not all that complicated and, over the long haul, a few long nights in front of your PC might save you a bundle in engineering costs.


Now, I have no problems with consulting an engineer if the situation is beyond me, but your situation sounds like a good one for you to explore some other options and keep the cash.


And I'm not plugging Boise Cascade....Weyerhaeuser, Roseboro and some of the other mfgs of engineered products may have the same resources available.


For BC's software, call 1-800-232-0788 or email them at  bccalc_support@bc.com


Good luck!



 


Edited 10/6/2004 12:40 am ET by Notchman

 

(post #96302, reply #21 of 25)

There were double 2x14s over our double garage door (about 18 feet, IIRC). The center sagged over an inch. (Just eave side of truss roof above.) Replaced with double LVLs (1.75 x 11.75 or something like that) and, after temporarily removing jacks, measured a sag of about 3/8". Jacked back up and shimmed out that amount. No measurable sag now.

I'm not sure I'd trust 2x12s over that distance at all, based on that personal experience, regardless of what the charts may say.


Edited 10/6/2004 9:54 am ET by DanH


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First off (post #96302, reply #25 of 25)

First off, that is not a header.

Secondly, what type of ridge do you have?  If you have a ridge beam then your beam would only be carrying your ceiling load which is near nothign, ok not nothign but small.  If a ridge beam and you want the attic space to be livable, ie carry live load of people, then your beam would be carrying a greater load (12 feet x 19 feet x 50 (live and dead load = 11,400 pounds or 600 per linear foot.  Need Glulam or LVLs.  Tables are easy to find and use!

If you have a ridge board, then the load has to be carried somewhere.  If you tie teh rafters together with collar ties and teh ceiling joists I am not sure how to calculate your beam.  I think alot of your issue in that case comes down to the specs of your hangers for the ceiling joists to beam connections since the ceiling joists are in tension and would tend to want to pull away from teh beam (with teh beam actually not carrying much of a load unless you have live load of a functional attic.

If you understand the issues all of this can be figured out with tables and the internet.  I have paid "professionals" money to confirm my work and two things happen they confirm my figures, and two they miss stuff which if not addressed would cause structural FAILURE,  So much for money, money, money. 

.