I want to replace a Basement slider, I have one floor above plus roof. The new door I have is 81.5" and opening is 80.5. There is currently 2 2x10's for header. I need that additional room. since the door is 6 ft. wide, I heard I can replace those 10's with 2 2x6 and be safe? Anyone know if thats OK? and if not is there any other way since the bottom is on concrete footer..
With the load of the floor above and the roof, an opening of that width typically requires two 2x10's. The deflection that you'd experience with two 2x6's would probably affect the function of the door, not to mention it would be structurally unsafe!
Whoever told you that you could use 2x6's gave you some bad advice.
The only way I could see you getting away with two 2x6's is if you were to bolt a 1/2" steel flitch plate between them.