The front of our house is pretty plain so I want to add to the roof by adding a front porch. It is going to be a 4 to 12 pitch gable end and it will be all open. Two small square columns to hold up the front. My first question. Because it is open and not enclosed does this make it a foyer? Next: after I strip off the shingles I am going to lay 2x6's on the sheathing and nail them to the trusses to make a base for the valley on each side and to have a place to nail the jack rafters. How do I calculate the angle where the 2x6's meet at the top and is this the correct way to handle this? Third: I want the lower part of the original roof to show so I was going to plan it out with the columns being 18" higher than the facia of the old roof and then run 2x12's from the top of the columns to the roof for the new trusses to sit on with the one closest to the old roof attached to the ridge pole. Does this sound correct or am I going to run into problems?