Shaving concrete garage header

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Old 10-04-15, 10:36 AM
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Shaving concrete garage header

I have a detached garage that I'm converting into a more finished space, and plan on replacing the garage door with a french door and some side lights. I want to go with 7ft doors, however, I'll need to cut 2 inches off the header to make room. I want to confirm that with the 2 inches missing, there's still enough header left for the span, without having to add a support column in the middle. The trusses run parallel to the header so I don't believe the header is supporting roof load.

My question is, are there concrete header span tables on the internet which will give me the information I'm looking for and where can I find them? I've done quite a bit of searching already.
 
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Old 10-04-15, 11:00 AM
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I don't think you'll find span tables for a concrete header. So much depends on how your header is constructed. One option might be to research replacing your concrete header with traditional dimensional lumber, LVL or steel. Since those are more uniform/common materials there are span tables on the Internet so you can quickly see if they are a viable option.
 
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Old 10-04-15, 11:01 AM
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What size header and what is the total span? What good would concrete header span tables do you? If, when you tell us, the span is too much or the width of the header is too small, you may could be relegated to a steel I beam, which IMO would be much more adaptable to your new door height.
 
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Old 10-04-15, 12:06 PM
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The span is 14 ft' , header is 8"thick X 17" tall. Also, constructed post Hurricane Andrew with revised building code, so I'm sure it contains loads of rebar and over engineered with lots of margin built in. I'm just trying to determine if I'll still be in the safe margin after removing 2" inches, or if I need to reduce the opening or support the span with a column at the mid-point and use an alternate door/sidelite configuration.
 
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Old 10-04-15, 12:29 PM
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I would like to know how you would cut the 2" off the header in place? Fractures can happen pretty easily.
 
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Old 10-04-15, 12:34 PM
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Never heard of a 7' door.
How much room is there now? A 6'8" door only needs just over 6'9". Going to be tight but should work.
Is this a gable end?
Got a picture?
 
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Old 10-04-15, 01:14 PM
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Gable end roof.

7 FT doors are sometimes used for both indoor and outdoor remodeling projects in my area, if you don't mind re-framing interior openings or cutting through headers as I want to do. For exterior french doors, the extra 4" of glass makes a big difference when looking outside, a much nicer view in IMO.

I know a concrete cutter with a nice hydraulic wall saw with a guide on it. I will tapcon in a straight piece of lumber as a guide and he'll cut through it nicely in one pass.
 
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Old 10-04-15, 01:43 PM
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I guess it depends on the type of garage door you are installing, but the 7' Doors that are common to my area will still fit with no issue even if the opening is 2" shorter. This is becasue the door actually sits in the inside of the room of the framed opening, and not under the header, like a traditional man door like in the image below.

[ATTACH=CONFIG]56967[/ATTACH]
 
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Old 10-11-15, 09:51 AM
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But I have to ask--Exactly what will be your backup plan after the concrete cutter removes the main longitudinal (tension) reinforcing steel from the beam? In simple span construction, it's usually placed within 1-1/2" or 2" from the bottom of the member. Also, all of the shear-resisting, vertical stirrups will be compromised by cutting off their bottoms.
 
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Old 10-11-15, 10:36 AM
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Also, if a 8" x 17" header was installed I would bet that that was the size required to do the job. I doubt they installed one larger than required and certainly had no idea or intent that someone would come along and try to cut a couple inches off of it. At the very minimum you need to consult with a structural engineer if you wish to seriously consider cutting the header.
 
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Old 10-11-15, 10:54 AM
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your ins co will love you if they find out
 
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Old 10-11-15, 07:24 PM
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Stadry, your sarcasm could be misleading. As in if the OP is just a youngster, having little real world life experience, he could be taking you seriously, and construe your advice as a green light to go ahead with his absurd plan. If and when the beam collapses (for reasons I mentioned previously), seriously hurting or killing people, and a few hundred thousand (or even millions) of $$$ are paid out for claims, he will be black-listed by all major insurance carriers. Meaning future home ownership will never happen.
 
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