"TP" wrote in message
news
I have two 2x10’s 18 feet long supported in the middle by one
2x4. Windows are now in these openings. I’d like to remove the
center 2x4 and replace the windows with a 16’x 7’ garage door.
What size (thickness) flitch plate would be needed to strengthen
the 2x10’s to support the open span? (Keeping within the 9¼”
height.) Single story, 4/12 roof, rafters are perpendicular to
header. No live load, just ceiling joist. Snow load for western
NY. Next wall parallel to header is 22’feet away.

Thanks
TP

The calculations to determine the individual tributary loads and the
resultant header load are pretty straightforward, the flitch plate
calculations a little more involved. I don't think you are going to
find anyone on a newsgroup (even a PE) who will be willing to give
you an absolute answer.

I'd suggest you contact a local engineer...