OP, the first thing you need to do is get your house plans and see how the lintel beam is installed. I suspect it goes ONLY from support to support, so this will be a much bigger project as you would need to replace the lintel beam for the wider width. I am sure this will require an engineering firm to design the new beam, as well as all of the permits. If you are in Sumter County and your house is less than 10 years old you should be able to get your plans from the building department.
IMHO, this will be expensive, and I am not sure if you will find hurricane rated garage door for this width.
As an option I would suggest 2 9 foot (9.5 foot) door with a center support for the new lentil beams, this would allow more conventional garage doors, openers, etc.
__________________
Pennsylvania, for 60+ years, most recently, Allentown, now TV. 
|