# Engineered beam design



## Makai (May 30, 2011)

Hi looking for enough information to design and build my own beam to carry across two car garage entry. Right now there is a 4×4 in the middle and I'd like to biuld a beam to eliminate the 4×4, hold up the roof (single story), and mount a garage door. No worries about snow weight here in Hawaii. Thanks in advance!

Alan


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## dkirtley (Mar 11, 2010)

Just making a wild guess, at at least 16 ft for a 2 car garage door, you are up in the range of 2×12's doubled and maybe think about getting a steel I beam. How to hook it in to be good for what you might need to satisfy the requirements for hurricane force winds would be best decided by someone in your area with that experience. You don't just have to worry about it holding the roof up. You have to worry about holding it down as well.


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## DMIHOMECENTER (Mar 5, 2011)

All… Two (2) 2×12's with an OSB sandwiched is NOT good for but about 12' of span if there are no rooms above.
If the man has a 2-car garage and the two doors openings are 9 feet (a minimal guess) then he has an 18 foot span with the 4×4 removed. That is BEYOND 2×12 header FOR SURE. Glue lams will most likely be the cost-effective solution (not I-beam), since the new header can be easily set to a king stud on each end with 2 or more jack studs beneath each end of the header.

If I were at work right now, I could tell you the size of the glue lams needed, but that is something you will want the supplier to figure for you when you tell then your overall length required and the span that it is taking. The liability will be on them when you do it that way (and usually with a professional engineer's seal as well).


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## DMIHOMECENTER (Mar 5, 2011)

LMAO. Don't disagree with me. Just give the man the right advice: by telling him to consult the span charts in the code book.

I regularly purchase glue lams and LVL's and floor scissor trusses and engineered roof trusses (common and knee wall). Glue lams are not expensive (but they are more expensive than the 2×12's that will not support that span to code). They are in stock and ready to go at our local Probuild in normal sizes. Anything extraneous gets ordered from the local Woodford plant FOR THE SPAN with engineers stamp as well.

I say do it right (and to code) or not at all.


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## DMIHOMECENTER (Mar 5, 2011)

Georgia is on the East coast. Around here, we don't build rake walls in two parts unless a vaulted area is higher than 16 feet. That is very rare here. Most homes are not vaulted here… either two story (mostly Williamsburg or derivative) or high ceilings (9'.10', 12' usually) with crown, sometimes trays, once in a while coffered, etc.


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## DMIHOMECENTER (Mar 5, 2011)

We don't sell any building materials. Never will. Only everything after sheetrock and trim… flooring, lighting, cabinets, appliances, windows, doors, etc. So there is no material sales skew to my comments at all.

No ego at all. I'm just really funny about anything to do with load bearing recommendations and design. Not funny, actually very serious. I don't know it all, either and never will, but I do know some things.

The span charts do not vary by locale. Codes may, but not the charts. they vary in that they are specific to the type of span, the materials used, and the live load that they may carry, etc.

The 2×12 may carry it without failure, but it will have sag and deflection and always be close to failure.

Really, I'm not trying to be Mr. Wizard. The international code books has the charts but I'm at home. And I'm not trying to be argumentative, but lets both make sure our friend gets good advice if nothing else.

Read this: http://www.carpentry-pro-framer.com/garage-door-framing.html

I didn't even want to get into whether the 4×4 in the middle of the existing span that's header is made of ??? 2×6 or 2×8 or 2×10. That's asking for the teenage daughter to bump it and the world comes crashing down if greatly undersized. It happens. I have repaired these done by others.


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## Makai (May 30, 2011)

Thanks everyone, lots to digest and I'll get some measure measurements up soon. But i was thinking of building it myself and am hoping to find info on what I need and how to build it. Everything costs more in Hawaii but I have the tools and the time.

Alan


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## devann (Jan 11, 2011)

Without getting into too much detail about your particular situation here's a book that explains a lot of what you're looking for. It has a section explaining how beams work and tables of different species and sizes of wood that you should find useful. There are other sections of the book that come in handy for anyone with a workshop.
http://lumberjocks.com/reviews/1922


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## DMIHOMECENTER (Mar 5, 2011)

Jeez. What is the difference if he buys two 2×12's versus two gluelams ? Same process/procedure. He will be building it himself. The debate is over the exact type of components he will be using.

@Makai, give these guys a call and get a free quote:

HPM BUILDING SUPPLY - HILO 
HI, 96720 HILO, 380 KANOELEHUA AVENUE

or

HPM BUILDING SUPPLY - KONA 
HI, 96740 KAILUA KONA, 74-5511 LUHIA STREET

We represent over 2,200 lines of pro grade lumber, building materials and tools Plus, we ourselves manufacturer to your custom specifications wood trusses, metal roofing, and pre hung doors For those looking to build a new home, we also offer 14 proven house plans, building materials conveniently packaged to save you money, and the know how to help save you time and headaches And with five locations and the largest trucking fleets around, we've always been just around the corner from your Big Island projects But now with our expanded Honolulu sales office, we can also easily service your projects on Oahu, Maui and Kauai
_

Let us know how it compares to dimensional 2×12's and also what they recommend (from their charts) for the span.

ho'omau akahele, maka maka ;=)


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## Grandpa (Jan 28, 2011)

I inspect homes regularly that have who knows what for headers over the garage door. Most of them sag so I would guess that most of them are under built. Build to the maximum and not the minimum. Build it right and you will save money since you won't need to rebuild it in 5 or 10 years. Local codes come first then make it strong. In my area it is not uncommon to use a sheet of 14 ga. steel between the 2×12's if that is what you use. Nail it to one 2×12 then bolt the 2×12's and OSB together. Maybe that is what I see sagging. It is often difficult to determine what doesn't work after you cover it with wallboard and bricks.


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## rimfire7891 (Jun 15, 2010)

Grandpa has right idea.
The piece of steel sandwiched between the 2x lumber will increase the bending resistance way more than just adding more wood. If you use 3/4" ply instead off 2x lumber you can cut the ply to what ever width you can fit in the space. The wider the better. Have the metal sheared to the same size as the ply width and screw and glue it to one side of the ply. PL premium works great for the glue. The ply stops the steel from twisting off the vertical axis.

Just built one to support loft in a 24'x24' wood shop. Used 3×3/4" ply's on each side of a 5/16"x12" steel flat bar 24 feet long. Offset the joints in the 8×12" foots length's of 3/4" ply. Did the math on the beam and the deflection was less that 3/8" at the centre with 30 pound per square foot live load ( typical values are 30 to 50 lbs per square foot live load) on the whole floor 576 sq ft x 30 lbs is 17280 lbs equals about 8 tons. There is no way it will fall unless it gets an stupid load on it. The loft is for storage rather than live load.

The strength come from the vertical dimension, that why I beams work. The top and bottom flange doesn't add much except to keep the vertical members from moving off the vertical axis. The ply wood /steel beam is cheaper and easier to attach other materials to.

Did the math on a glue lam instead of the site built beam above and it had to be 15" width and 4 ply's and the weight starts to defeat the purpose. The cost was twice as much for the glue lam compared to the beam we built.
Better beam and less cost to boot.

modulus of elasticity ( E) for wood beams is average 1,700,000 psi
modulus of elasticity ( E ) for steel is 29,000,000 psi 
Steel is 17x stiffer than wood.

just a few thoughts

Makai built your own. More fun and knowing you did it priceless.

Thanks jb


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## Bertha (Jan 10, 2011)

I have no idea what you guys are talking about but whatever it is, you both know a lot about it. This is one of the more interesting threads around here. Carry on like I never said anything…..


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## devann (Jan 11, 2011)

Grandpa; I've used the "poorboy fletch upgrade" before however with a slight twist. We allow the metal to hang out the top and bottom enough to bend at a 90° angle in a Z fashion. This should only be uesd for headers shorter than 11' in length. On the longer headers we use 1/2" steel if making the header wider than 3 1/2" is not feasible.


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## Sawkerf (Dec 31, 2009)

Before you start buying material and banging something together, you should check with your permit folks and get their take on a DIY beam. They *might* go along with you building one, but don't be surprised if they want it built to a stamped design by a structural engineer.


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## Dark_Lightning (Nov 20, 2009)

I'm willing to bet that the "4X4" has the other 12 to 16 inches of height buried in the wall above. There is NO way a 4X4 made that span, unloaded, even, without sagging like a banana. A 4X4 over that length is completely out of bed with reality. That's appropriate for a 4 foot window, not a garage door.


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## rimfire7891 (Jun 15, 2010)

AtomJack,
The 4×4 is the support in the middle of the two existing garage doors not the header. That's what Makai wants to remove and have a single span supported at the outside nib walls.

Thanks jb


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## DMIHOMECENTER (Mar 5, 2011)

We started with the man asking what he needs to span a double carport opening. Two (2) 2×12 with OSB center suggested.

See Span chart for headers supporting roof and ceiling here: http://napasolanoicc.org/Links/IBCSpanTables_NapaSolanChapterFinal.pdf

So, 2 ea. 2×12 is not even close for a 16' span. (Neither is 4 each 2×12, by the way).

The steel recommendation would work, but before buying any steel, just price the glue lams for this application.

Rimfire7891's example is for a live loaded loft with a 24 foot span and that most likely was the most cost-effective route for that application. I had to do the steel center girder for a 30×30 and for a 30×70 in recent years. It made sense.

By comparison, this little 16 ft. one story span exterior wall w/ load only roof and ceiling is like comparing raisins to prunes. It needs to be what it needs to be. No less for sure.

Grandpa (a home inspector) has seen sagging garage headers. So have I, except I've had to replace them and most are 16' and 18' spans with 2 each 2×12 with OSB center.

From the above framing site… "Door Width and Header Size

We've all seen 16' 2×12 garage door headers sag, even in a gable wall let alone in a load bearing situation. With the use of micro lam beams, getting the proper size header should be easy. Check with your local building department."


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## devann (Jan 11, 2011)

*"We've all seen 16' 2×12 garage door headers sag, even in a gable wall let alone in a load bearing situation." *
All gable walls bear their load straight down. This is the reason for the header sag. Even a gable roof truss bears it's load upon what ever it is sitting on along the lentgh of the wall. A "common" load bearing roof truss transfers it's load to the ends at the outside walls. Rafters bear their load at the outside walls and the ridgeboard. The ends of the ridgeboard pick up their bearing straight down from a framing member, wall or beam.


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## DMIHOMECENTER (Mar 5, 2011)

Yep. Pretty much ^^^ and the point being that a gabled over exterior wall span typically has less load than a "rafter and joist" loaded span.


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## Makai (May 30, 2011)

Measured the span between the hollow tile wall on the right and the front left corner 4×4 upright, garage opening is 22', with a 4×4 in the middle. The garage is open on one side, the back joined to the house, the right supported by the hollow tile laundry room, the left is open supprted by two 4×4's, middle right and front right.

We just moved into the house on July 1st, it was built in 1960, single wall, 1" redwood T&G. My thoughts are to build a "storage" workshop on the right of the garage, it will support that side and eliminate two of the 4×4s. The beams that these 4×4s carry run from back to front and are big, 6×8 on each side and a 6×10 down the center. The roof is just plywwod with composition paper, no plans to add any rooms over the garage. The new front beam / rafter (terms misused!) would support the roof and provide mounting points for a garage door.

Not sure, maybe going with two garage doors and keeping a middle support is better. Not going to be able to afford a stand alone workshop so I'm using the bedroom that butts up to the back of the garage for stationary tools and the storage workshop for my portable TS, miter, and dust collector. Wheel them into one of the stalls when needed.

Ordered a few books, including "Workshop Math", and others. Reading all the links too! Thanks to everyone.

Alan


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## rimfire7891 (Jun 15, 2010)

Hi Makai,

Thanks for a little more info.
If you have a choice between one garage door or two would definitely go for two. The header required is way less than the 22' span. The header depth rule of thumb is 1" for every foot of width of opening. So if you have two 10 foot opening then a couple of 2×10's with a 1/2'' ply spacer will work fine. I would use two 2×12" just so you over engineer it a little.
Less heat loss in my part of the country, probably less heat infusion in your part.
If you have a two car garage side by side it is better to have more space in the middle so you don't bang car doors and have space for egress from the most used car into the middle away from the walls.

Thanks jb


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## rusty2010 (May 26, 2011)

Mr. Makai,
I am a Design/Builder located in Indiana. Take David Grimes advice, build to code. The other suggestions are good and knowledge based. Your local code determines hurricane, seismic shift and other oddities we don't experience. Take a drawing and pictures to the plan commission. Their sevices are free. I seen a lot of folks try and wing it without the proper skills and knowlege. They keep me very busy. Good luck.


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## Grandpa (Jan 28, 2011)

Good advice Rusty. Take it Makai and run with it. Good luck and remember when you go with the cheapest there is usually a reason it is that way


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## MrRon (Jul 9, 2009)

Making a glue-lam is not a DIY task. Glue-lams are made in presses that exclude air pockets and the wood must be flat and free of irregular surfaces. It is an engineered product. I wouldn't attempt it if I were you. You possibly might male one yourself, but you would have to "over-design" the beam with something like 3-2×12's put together with resorcinol glue and lots and lots of C-clamps and that will be expensive.


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## Makai (May 30, 2011)

Aloha,

Mahalo to each of you for taking the time to reply with your experience and knowwledge. LumberJocks is a friendly and helpful place to discuss ideas. My take away is follow the code, glue lamanates are made under high pressure, and consider using steel. I've order a few books based on your advice, Workshop Math arrived yesterday - what great resource! A book on building codes and house framing are on the way. In the end this will be a permmitted project done to code. I'm leaning towards steel and doing the coverup and trim myself. This means it won't happen for a year, but it will be done right.

My day job is network administration so my woodworking knowledge comes from helping my Dad build boats and the home we lived in. I remember helping him use resin glue and C-clamps to make the laminated frames for the Albarbet, a 36' sport fishing boat that made many interisland trips in some very rough seas, including one accrossing of the Molokai channel that had us all holding our a**es surfing down 20' swells and praying that our single Cummings diesel would power us up the face of the next one. My Dad, Uncle Ahoi, Uncle David, and I were very quiet when that first channel bouy came into sight as the last trace of daylight disappeared from the sky. My Dad was a true do-it-yourself guy but knew his limits too.

Alan (Makai)


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## MrRon (Jul 9, 2009)

To be legal, a glue-lam has to have an engineer's stamp of approval, same as for wood trusses.


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