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Engineered beam design

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Forum topic by Makai posted 1137 days ago 3518 views 1 time favorited 25 replies Add to Favorites Watch
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Makai

8 posts in 1186 days


1137 days ago

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


25 replies so far

View David Kirtley's profile

David Kirtley

1276 posts in 1630 days


#1 posted 1137 days ago

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.

-- Woodworking shouldn't cost a fortune: http://lowbudgetwoodworker.blogspot.com/

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David Grimes

2072 posts in 1272 days


#2 posted 1137 days ago

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).

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

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David Grimes

2072 posts in 1272 days


#3 posted 1137 days ago

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.

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

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David Grimes

2072 posts in 1272 days


#4 posted 1137 days ago

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.

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

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David Grimes

2072 posts in 1272 days


#5 posted 1137 days ago

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.

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

View Makai's profile

Makai

8 posts in 1186 days


#6 posted 1137 days ago

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

1735 posts in 1325 days


#7 posted 1137 days ago

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

-- Darrell, making more sawdust than I know what to do with

View David Grimes's profile

David Grimes

2072 posts in 1272 days


#8 posted 1137 days ago

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 ;=)

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

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Grandpa

3098 posts in 1308 days


#9 posted 1137 days ago

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.

View rimfire7891's profile

rimfire7891

123 posts in 1535 days


#10 posted 1136 days ago

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

-- Playing with wood and metal for the last 50 years, driving and building Land Cruisers for the last 40. Experience is what you get when you don't know what you are doing.

View Bertha's profile

Bertha

12951 posts in 1326 days


#11 posted 1136 days ago

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…..

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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devann

1735 posts in 1325 days


#12 posted 1136 days ago

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.

-- Darrell, making more sawdust than I know what to do with

View Sawkerf's profile

Sawkerf

1730 posts in 1701 days


#13 posted 1136 days ago

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.

-- Adversity doesn't build character...................it reveals it.

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Dark_Lightning

1694 posts in 1741 days


#14 posted 1136 days ago

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.

View rimfire7891's profile

rimfire7891

123 posts in 1535 days


#15 posted 1136 days ago

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

-- Playing with wood and metal for the last 50 years, driving and building Land Cruisers for the last 40. Experience is what you get when you don't know what you are doing.

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