Expert: Daniel Humphrey - 11/4/2008

Question
I'm building a 24wideX30deep detached garage.  I'd like to install an 18ft wide garage door on the 24 foot (non-load bearing) side and am curious what header thickness is needed.  I know that my city requires a header of two 2X12 with 1/2" plywood in between for a 16 foot wide door.  Do I need to have 2X14 for an 18' door or will 12" still suffice?  Do I still need 2 top plate 2X4's on this wall or would one be enough?
Thanks.

Answer
Chad,

The header can be a 2x12 sandwich, as specified. It's important that the header itself be tied securely to a full-length post on each side of the door. These posts should go from floor to top plate. And yes, you should go ahead and double the top plate, if it sits on jack studs abobe the door header. A double top plate helps you tie the end wall to the side wall and gives you more fastening area for sheetrock near the ceiling.

The wider door will be a little heavier, of course, and will require some larger springs and solid hardware, all with solid attachement to the wall itself. Some of these attachement points are on the full-length posts on the sides, and some are on a center support above the header. Take a look at the pamphlet that comes with your door before you do the framing.

Daniel