HEADER DESIGN FOR DORMER JACK RAFTER
HEADER DESIGN FOR DORMER JACK RAFTER
(OP)
hello,
I am reviewing and stamping a set of plans for 44x28' A frame house with 12/12 pitch roof. the owner wants me to add a dormer for the upstairs bathroom. on the building section I noticed a skylight detail with a header above the skylight. the header is shown square to the rafters (rafters are 2x12 @ 16" SPF #2).
question: would this header be designed to act as a normal beam with strong axis and applied loads vertical, or is it the more complicated out of plane bending.
the dormer will be 8' wide so the header will have significant load on it. the header will be framed into tripled rafters on either side of the dormer. thanks in advance for any advice.
I am reviewing and stamping a set of plans for 44x28' A frame house with 12/12 pitch roof. the owner wants me to add a dormer for the upstairs bathroom. on the building section I noticed a skylight detail with a header above the skylight. the header is shown square to the rafters (rafters are 2x12 @ 16" SPF #2).
question: would this header be designed to act as a normal beam with strong axis and applied loads vertical, or is it the more complicated out of plane bending.
the dormer will be 8' wide so the header will have significant load on it. the header will be framed into tripled rafters on either side of the dormer. thanks in advance for any advice.






RE: HEADER DESIGN FOR DORMER JACK RAFTER
RE: HEADER DESIGN FOR DORMER JACK RAFTER
RE: HEADER DESIGN FOR DORMER JACK RAFTER
RE: HEADER DESIGN FOR DORMER JACK RAFTER
DaveAtkins
RE: HEADER DESIGN FOR DORMER JACK RAFTER
In the above problem, the 8' wide dormer becomes structural. Shouldn't the designer be equally concerned about the triple 2x12 in-construction rafter beam on each side of an 8' wide dormer, which receives the point-load of the header in question? If the rafter-beam was spanning the long direction (44'), LVL might be required, especially if you're trying to hold l/360.
RE: HEADER DESIGN FOR DORMER JACK RAFTER
RE: HEADER DESIGN FOR DORMER JACK RAFTER
From your posts ("reviewing and stamping a set of plans", "design check") it sounds like you are "plan stamping" this project; you are perhaps stamping a set of plans drafted by the owner/contractor/designer and not prepared in your office. If this is so, then I would respectfully suggest researching the ethics and legality of perform professional services in such a manner, as many licensing boards take a dim view of such a practice.
TECHNICAL RESPONSE
As another post suggests, I would simply detail the header as plumb, otherwise you should consider biaxial flexure in the header. In reality, as the diaphragm/sheathing is far stiffer than the weak axis of your proposed header, you can also consider the weak axis as "braced" IF you detail the load path of this bending component into the sheathing (like a sub-diaphragm). You would need to check the sub-diaphragm shear and develop the sub-diaphragm chord forces back into the main diaphragm. You could also maybe put a collar tie in that location...
RE: HEADER DESIGN FOR DORMER JACK RAFTER
Don Phillips
http://worthingtonengineering.com
RE: HEADER DESIGN FOR DORMER JACK RAFTER
I think I am going to make the header plumb. thanks for all the input - its what makes this forum great.