I have a porch roof that the previous homeowner did half arsed, 4 pillars set in concrete (link fence posts). Now one side is sagging badly. My brilliant idea is to to replace the 2x4 (4) with 2x6. I have already gotten the post pillars to support the structure. So here is my issue. Would it be best to auger out a large hole and make a concrete pier rather than to just just pour concrete and set the posts? I have heard old timers talk about using gravel at the bottom to help keep the post from sinking but I am wanting something a little more sturdy
Gravel will not do you any justice. It is just a cheap way to go deep in ground to get to good bearing soil if it needs to go really deep. Pole barns, for example, are built with 6X6s set in the concrete 4' deep, for a porch roof if it is small enough it won't need 6X6s but 4X4s will suffice if the roof is not too high.