Well I built a garage here last year and I have a 16' door opening trusses running the same way as his and I was required to use a 4x12 minimum for the header on mine.
Anyone ,not versed in construction spending serious money on a building project, should have a set of approved plans. Also be sure to hire a reputable contractor with a building license. Poking around the internet is a great way to expand your ideas but I would be very cautious with free advise. There are a lot of home handymen, do it yourselfers, that throw out a lot of misinformation. Also be aware that different parts of the country require different building practices. Snow loads, freeze depths, ect. So what some internet expert is telling you may simply not apply in your area.
If you do hire a contractor please don't question his building practices after some internet hack tells you that your contractor is not building it correctly. Hire someone you fell comfortable with and let him do his job.
Anyone ,not versed in construction spending serious money on a building project, should have a set of approved plans. Also be sure to hire a reputable contractor with a building license. Poking around the internet is a great way to expand your ideas but I would be very cautious with free advise. There are a lot of home handymen, do it yourselfers, that throw out a lot of misinformation. Also be aware that different parts of the country require different building practices. Snow loads, freeze depths, ect. So what some internet expert is telling you may simply not apply in your area. If you do hire a contractor please don't question his building practices after some internet hack tells you that your contractor is not building it correctly. Hire someone you fell comfortable with and let him do his job.
Most of us are recommending just that. A double 2x12 with a 1/2" plywood sandwiched in between the boards.