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What size header for a double car garage door

Posted by tnladyhillbilly (My Page) on
Sun, Oct 21, 12 at 23:03

I have a 22 ft load bearing wall with a 18' 3" header constructed out of 2 2x12s with 1/2 inch plywood sandwiched between for a double car garage door. The header and wall have been up since last Thanksgiving and today I realized that the middle has sagged 5/8 of an inch. What size and kind of header should I have used to prevent this from happening?


Follow-Up Postings:

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RE: What size header for a double car garage door

You should have used a laminated beam for strength IMO.


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RE: What size header for a double car garage door

It should be specified by an engineer as we do not know what type of load this is carrying.


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RE: What size header for a double car garage door

To answer your question we would need to know the load on the beam. You need to tell us which way the roof framing spans, the span of that framing, the configuration of the roof, the roofing material and the code required snow load, if any.

All we can tell you from your limited description is that the deflection is already at the allowable limit for the maximum design loading condition so it will probably get worse.

I don't see how this beam could be load bearing for this size opening. cartod is right, you would need a laminated veneer lumber beam of greater depth.

An engineer should look at it.


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RE: What size header for a double car garage door

The truss ends set on top of the 22 ft wall. Two foot on center. The trusses are 28 ft long over a 26 ft deep garage. The roof is 6/12 pitch with osb sheathing and asphalt shingles. I am on disability and have been building this house as I could afford it for the past 6 years. At this point hiring an engineer is out of the question. I met codes when I installed this header but obviously it should exceed codes to operate correctly.
Thank you for your replies.


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RE: What size header for a double car garage door

Unfortunately, you are mistaken about the code compliance of this beam. A building code does not give a size for a long span girder; it must be designed by an engineer. This one has less than half the strength required to meet "acceptable engineering practice". You should shore the middle of the span with a 4x4 post until you can afford to have it replaced, especially if you expect snow.


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RE: What size header for a double car garage door

You had a span of 18' and used a 2-2x12?

For a span that is 16', I usually use a minimum of 3- 1 3/4" x 11 7/8" LVL. (30 pounds snow load)
Who provided the beam? In many cases when the builder is not using an engineer, the lumber/truss provider engineers's is required to sign the documents. You can take a look at the trusses shop drawings to see what they specified, otherwise, go to the lumber company you used. They might be able to help you with this.


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also

The building code header table would limit this beam to a span of 8-5 ft. An engineer might let you span 9 ft. So, adding a post will make the beam code compliant.

To be able to remove the post you will have to replace the two 2x12's with two 1 3/4" thick LVL's (laminated veneer lumber). The lumberyard can get the manufacturer to give you a stamped design for free. If you are lucky the new LVL's will not be taller than the existing 2x12's and will be easy to install. However, you will need to temporarily shore up the trusses without damaging their bottom chords.


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RE: What size header for a double car garage door

" I met codes when I installed this header "

Not very likely.


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RE: What size header for a double car garage door

When I said I had met codes when installing this header I assumed that me talking to the building codes manager in my county prior to building and installing the header and telling him what I was doing and asking him if what I was doing would meet codes and be sufficient and him answering yes was correct. Now whether of not he was correct (I am assuming not since the beam is bowing)I don't know.
Thanks for all your replies. I have talked to several builders in the area (not the codes manager..lol) and think I have a solution.


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RE: What size header for a double car garage door

Only someone who has been taught how to determine the correct load on a beam and how to size it could help you. A building inspector or a builder might have that training but I would assume they don't if it were my garage.

What you still don't seem to understand is that the building code offers no prescription or table for the sizing of a beam this long other than to say it must be designed according to "accepted engineering practice". In most jurisdictions that means a licensed engineer. It is doubly important to have a professional designer involved if the walls on either side of the opening are less than 4 ft wide because they might not offer enough lateral resistance to keep the garage from collapsing in a wind storm.

Unless the building inspector has some kind of beam design guide that the state allows him to use or has been trained as an engineer or an architect, he should not be offering structural advice to a homeowner and that goes for builders too.

Until you get a professional involved either by hiring one or asking the lumberyard to ask the manufacturer of their LVL's to give you a design with a stamp on it, you are perpetuating a very serious structural mistake and someone could get hurt or you could have a major financial loss.

If it snows the roof could collapse with no warning so put the post under the beam and go talk to your lumberyard or take a builder with you to the lumberyard. Don't do anything without an engineer's stamp on it.


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