typical wood header detail - dropped header or below double top plate

[eng003]

I got into a conversation concerning typical wood frame construction header details. Being discussed was the pro's and con's of a header directely under the double top plate w/ cripple studs and a single plate over the window vs a header right above the opening. They both will do the job gravity speaking but my contention was that it is better to have the header right over the opening so as to provide a stronger member to distribute wind loads normal to the wall delivered by the window opening over to the king studs although I recognize the other method allows for easier adjustment of rough openings. Interested in others thoughts on this...

 

[msquared48]

I don't like the idea of setting the header high. It leaves to much structural design flexibility to the contractor and owner in my opinion, and they are not the designers. I always set the header at the top of the window and show it that way in my details. If they want it otherwise, then that would be a special design in my book.

Plus, if this is a perforated wall design, if the header is set high, then the area above the window would be lessened for the preforated design.



Mike McCann
MMC Engineering

 

[JAE]

For a 3'-6" wide window not sure it matters. For a 12' wide opening then you do have lateral wind to consider. Also matters how much wall is above the opening.

 

[nhstruct]

I typical have the header up high, and a double plate at the window. I have had to many cazes where the contractor srews up the elevation and has to cut out the header. This solves that issue, yes on longer spans you need to verify that the top plate can take the lateral loads. as far as perforated design, the double plate typically takes care of this issue.

 

[structSU10]

I typically set it at the top of window. Attached is a paper about headers, specifically the beam stability constant. It talks about what set ups allow you to assume a fully braced header. Basically setting it up has the advantage of saying its fully braced, otherwise it may not be and need to get larger.

 

[RFreund]

2 less cuts in a drop header application. Maybe 4 depending on jack (cripple) studs.

EIT

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