Darryl--I don't know what part of the world this is, but I would suggest that if you want to build a porch that will last, the columns need to be founded and anchored to concrete footings, the roof should be built at a pitch that will evacuate precipitation efficiently, and supported by a single or series of beams and rafters that are integral to your task. I am concerned that the work you are considering may be a bit beyond using the native materials at hand. Given that I see a block bldg, likely you are in an area with a lot of DIY projects. I would suggest that you do research re: indigenous pests and wind design loads in your area. If termites or other boring insects are an issue, wood may not be your best option, especially when in close proximity to the ground--building reinforced concrete block columns, if common, may be a good option. This way, any wood is kept well above grade, and if structural wood is rare or expensive, you minimize your expense. If you can find any architects, or engineers in your area, they will know the best course of action for you to pursue. Best of luck with your project.