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Old 04-26-2008, 11:34 AM   #1
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Garage Header Insight

Although I am a newbie to this sight, I spent most of yesterday reading here and found some great information on the construction and electrical forums. I have some questions concerning the enclosure of a double carport to a garage. I recently purchased a ranch style house built in 1968 with a truss style roof. It has a front loaded double carport on one end with the opening on the wall supporting the trusses.(not the gable end.) The opening is 19'2" wide. The other 3 walls are already enclosed. The header appears to be a doubled 2x10 supported on each end by bricked columns (don't know what's inside the brick) and a round metal pole in the center. I have considered framing the metal pole and installing 2 Nine Foot single doors but wife's Ford Freestyle is 9'2" wide at the mirrors and I see myself having to buy a heated power mirror because one of us forgot to fold it in before entering the garage. So my solution is to remove the pole, replace the header with a beam that will span the opening and put up a single 18 foot wide garage door. I have been a DIY person for many years but never had a need to make structural alterations so I am kind of in over my head here. No pun intended. Having recently relocated from the opposite end of TN (450 miles away) and no buddies to call on for the weekend, I am forced to hire a contractor to do at least the header part of this project. What I am asking for here is some information about sizing the header, calculating load weight of the roof trusses, metal beam verses LVL, etc. Also having moved from Memphis to Johnson City, I understand that snow load requirements and things of that nature are a factor? Who do you call about that? Building inspectors and permit office? I want to make sure that the beam will support the weight. Like I said, I will most likely hire this part out but I want to know what I am talking about and make sure they know what they are doing when interviewing contractors. Most likely, I will do the framing at the columns and hang the door myself and I want to know enough about the header installation to recognize anything that will cause problems for me when it's time to do my part. One thing I failed to mention earlier is the low ceiling (90") in this carport. Also the bottom of the existing header is 80" from the floor and cannot come down any due to the height of my truck. The existing soffit is attached to the outside of the header at 81" from the ground. I would prefer to not alter the soffit line or mess with the roof line at all because the roofing and gutters are less than 1 year old. Previous owners had just replaced prior to sale. Any suggestions, insight, or links to websites to further my research into this is greatly appreciated.


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Old 04-26-2008, 12:24 PM   #2
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Time to call the local building dept and contact an engineer. You should be able to do both with the building dept.
You will need a professional to redo the header,that part is NOT DIY.


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Old 04-26-2008, 06:06 PM   #3
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Skymaster's right. Your local inspector will probably be able to give you some names of engineers that do "piece work" type jobs for people without charging crazy amounts of money. There are engineers in my area that do this type of work for probably $300-400.

One thing you should consider about the header over your garage door(s). These headers are often part of a wind load resistance system, and the new installation will possibly be required to be brought up to current codes. Your local inspector can answer that question for you. The current code uses the garage portal walls at each end of the header to resist the shear and moment forces that the garage must endure. A normal wall has much more sheathing to resist these forces, but since the garage door is present instead of OSB or plywood sheathing, the portal walls are left to do all the work. The header itself serves to transfer these loads laterally, while also resisting the normal vertical loads. Nail pattern of the sheathing on the portal walls is critical, as is anchorage of the wall to the foundation and attachment of the sheathing to the header.

Whether or not your inspector requires a wind load design, I would recommend discussing it with your engineer. The International Residential code now requires it. I have seen what peripheral tornado winds (100 mph, sometimes less) will do to coventionally framed garage openings. The code's requirements are effective, even though the framers really hate doing it.

The size and material of your header depends on a lot of things. Among them is the dimension of the trusses that bears on the header (trusses' length). LVL is commonly used for spans that dimensional lumber can't make. You mentioned that headroom is an option, which will really hurt you if you're needing to make an 18' clear span with material comparably sized to a 2x10. That will be pretty much impossible with wood or engineered wood. You're probably looking at a 16" or 18" deep doubled 1-3/4" thick LVL, give or take. It is not uncommon to use steel beams for garage headers, but special measures have to be taken if your inspector will require wind load design as previously mentioned.
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Old 04-26-2008, 06:19 PM   #4
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thekctermite: Thanks for the input. You have confirmed what I thought. The building inspectors at city code enforcement are my best starting place. Coming from Memphis, I too have seen the damages caused by tornadoes and wind shear. I am told we won't see many tornadoes here on the side of this appalachian mountain, but hey, it only takes one, right? I am concerned about wind load and snow load. That is why I came here in the first place. I wanted to learn a little more about what to ask and discuss with the code guys. Thanks again for help. It is much appreciated.
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Old 04-27-2008, 08:55 AM   #5
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If you have brick on your walls around the opening, ask your engineer to size the beam for L/600. If not it should be L/480. That is the amount of deflection of the beam. It shouldn't take an engineer more than 10 mins to size the beam with a charge of $300-$500 including a sealed letter of recommendation. Like the above poster said, you may have to bring it up to code which may require the garage wall to act as a shear wall. It really depends on how much shear load you are taking to that wall. Sometime we sheath the back of the garage wall with osb to take most of the shear force and get around having to do moment conections at the garage opening.
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