Garage Door Header Sizing

[Air_N_Water2000]

I need to modify an existing shop garage door from a 12' x 12' door to a 12'-6" H x 12' door. I've found the required door, but need to modify the header to accommodate the larger opening. Currently, the header is a 3 1/2" x 15" beam, with another 3 1/2 x 2 1/2 beam on top of that then the double top plate. The 2 beams are not glued, just toe nailed to each other. I'm considering removing the top (small) beam, cutting the 15" beam down to 11 1/2" and adding a 2" angle iron along the bottom to increase its load capacity. Would this be strong enough of a header? My other thought was to build a plywood box beam 5 1/2" x 11 1/2". Which is the better option?

For a little more info, this is located in the Pacific Northwest with no snow load required. The roof is a hip roof made from engineered trusses. The opening is in the hip end and the main garage roof trusses run parallel to the wall.

Your thoughts/comments are appreciated.

 

[billconner]

You need to calculate load on the header and based on that determine what would work. It sounds like a non load bearing wall, so quite possible a smaller beam will work.

No offense, but I have no confidence in the cur the beam down an reinforce with angle iron.

 

[juddspaintballs]

If it is a hip roof, doesn't that wall have to carry some of the roof load? The way the OP talks makes it sound like it is a gable roof with the garage door on the gable end, however.

 

[crashmtb]

Call a structural engineer.

 

[billconner]

If it is a hip roof, doesn't that wall have to carry some of the roof load? The way the OP talks makes it sound like it is a gable roof with the garage door on the gable end, however.

But it's a truss roof, with trusses parallel to the header, so it is possibly like a gable roof with even less weight. I understand and have seen articles on this, but don't know what load it puts on header. And I'm not sure I interpreted the OP correctly.

 

[firebirdparts]

Bill, with a hip roof all four walls would be holding something up. That’s fundamental. Probably not too heavy but it can’t be “non load bearing.” That is fundamental to hip roof construction.

 

[LiketoFix]

I need to modify an existing shop garage door from a 12' x 12' door to a 12'-6" H x 12' door. I've found the required door, but need to modify the header to accommodate the larger opening. Currently, the header is a 3 1/2" x 15" beam, with another 3 1/2 x 2 1/2 beam on top of that then the double top plate. The 2 beams are not glued, just toe nailed to each other. I'm considering removing the top (small) beam, cutting the 15" beam down to 11 1/2" and adding a 2" angle iron along the bottom to increase its load capacity. Would this be strong enough of a header? My other thought was to build a plywood box beam 5 1/2" x 11 1/2". Which is the better option?

For a little more info, this is located in the Pacific Northwest with no snow load required. The roof is a hip roof made from engineered trusses. The opening is in the hip end and the main garage roof trusses run parallel to the wall.

Your thoughts/comments are appreciated.

Options;
I have done this with success on more than one occasion and I was taught the approved method and easiest most successful way without problems down the road is after you do your cut down Install a 1/4" thick x 11 1/2" wide x length steel flitch plate on end vertically that's preferably sandwiched between your header lumber and bolted together for strength as this was a typical application used by many a professional.
With that being said if your existing Beam is solid wood a heavy duty Angle Iron the proper size will carry the added load on that header but you have to use a 3/8' thick x 3 1/2" x 6" x Length piece of Angle Iron at a minimum and a 1/2" thick piece would be better! IMO!
I would not consider a plywood box Beam! IMHO!
LTF

 

[billconner]

Bill, with a hip roof all four walls would be holding something up. That’s fundamental. Probably not too heavy but it can’t be “non load bearing.” That is fundamental to hip roof construction.

But how much in a truss hip roof. Could be very little on walls parallel with trusses.

 

[Zeke]

You need to calculate load on the header and based on that determine what would work. It sounds like a non load bearing wall, so quite possible a smaller beam will work.

No offense, but I have no confidence in the cur the beam down an reinforce with angle iron.

Yes, flat steel on the sides is much better. The OP should look up flitch plates.

 

[billconner]

No doubt a flitch plate would work. Here's a good article on them: https://www.google.com/url?sa=t&sou...6sMDegQITRAB&usg=AOvVaw08pxWDQCykNjuOjyX12aRV

You still have to calculate load to design/select one. How much of the roof LL and DL actually bears on this header and what is design snow.

I'm not sure a 1/2" or thicker steel plate 12" wide and 13 to 14' long won't be harder to install and cost more than a properly sized lvl - albeit it might have to be 3 ply. I also don't know if two 2x12s aren't adequate.

 

[Zeke]

Well, If he wants to do an in situ modification, the option is there. Understand that I'm referring to an external plate, not a lamination. If it won't clac out then total replacement (or moving the existing header up) will be the best way, IMO.

The way I see it is that the 2.5 x 3.5 is a filler and doing nothing. The key is after moving the header up and reducing it's width, will it carry the load on the span? He gets 2.5" for free. The other 3.5" might be expensive.

 

[billconner]

Well, he hasn't returned since first post, so may not matter.