I have just purchased a townhome that had the carport converted into a garage. They used cheap 2x4 trusses that have rotted and are collapsing. I want to replace it and do it the right way.

The current wall construction is 2x4 studs with 2x4 top plate and sole plate screwed or bolted into the concrete. I have 3 vertical 2x4s on each side of the garage door supporting the sagging header. Those are attached to yet another vertical 2x4 stud that is the wall.

Since it was originally a carport, the main structure is 2 C-channel steel beams (about 3x8, I haven't actually measured) that run the width of the carport about 4 feet in from the front and rear. The roof is flimsy corrugated metal and supported by the steel.

The garage door way is ~16 ft.

There is an automatic garage door bracket that has to be (re)mounted to the header.

What should I use as a header that will not sag?

Will 2-2x12s work, or will they sag over time?

Could/should I use angle iron or something to reinforce them?

Are 3 vertical 2x4s on each side enough to hold a pair of 2x12s?

Thanks in Advance,

Willowbend