Laminate beam header for Pre hung door?
 

Looking to put a prehung door along a wall that will be built directly under a laminate beam in a basement.
Because the height of the floor to bottom of beam is only 80 1/2 inches,I will be unable to place a header in.
Thus,can I build two seperate wall sections,double studded for hinge and stop sides,and use laminte beam as a top plate for the prehung door?
Thanks in advance for your inputs.

Don't know why not. Just don't modify/cut the beam.

Why not frame the door properly and cut down the door? I just did this same exact thing.

Attachment 40871

in your situation where height is a issue, framing either side of the opening will be fine minus the top plate. the only thing i would make sure to do is have the wall deadly plumb and straight so the door can be hung properly. from there you will probably have to cut an inch off the door itself to allow for the jamb header and 1/2" space under the door

Thanks for the feedback,but since the door will already have to be 78 inches,I wouldn't want to lose any more height if at all possible.

Other than nipping off a 1/2 on the bottom for a capillary break against the concrete floor,a 78 inch prehung should fit in the 80 1/2 inch rough opening,or did I miss something?

no. just stating that you have a rough opening of 80 1/2" right now. im guessing the prehung itself is 80" unless you just bought a slab and are going to make a custom jamb. with the jamb you will need a header for the frame, so to keep a proper reveal and to have something to nail trim to over the door.