I am converting our carport to a garage. The existing opening is about 8' high by 19'+ wide. I am framing the opening to install two 7' high by 9' wide doors. The garage floor slopes from one end to the other, about 2.25 inches over the 19-foot wide width. When I frame the headers, they need to be 7' from the floor, but to do this would result in headers that are not level. I think that I should frame the headers level so that they are a maximum of 7' from the floor, resulting in one header that will be 7' from the floor at one end and about 6' 10+7/8" from the floor on the other end, and a second header that will be about 6' 10+7/8" from the floor at one end and about 6' 9+3/4" from the floor at the other end. Is this the best approach?

I want to put a 9'wide by 10' to 11' tall garage door in the barn I am rebuilding. What size does the framed opening need to be? Are there any other problems I may run into with this tall door?