Bricks, Masonry, Asphalt and Concrete - Bathroom room addition foundation

I am looking at turning an enclosed porch into a bathroom at my residence. The house is a 1920's single story house with a concrete brick foundation. The foundation on the porch is a different story. The room is approximatelty 12x6. One of the long and one of the short walls are actually exterior walls of the original house as the porch appears to be an addition. The two walls that are not tied into the old house are supported as follows: There is a concrete block and a half running lengthways up and down at the midpoint of the long wall and another identical setup supporting the corner. It looks like there may be another concrete block under grade supporting each of these supports. There is a sill running along the top of this setup on both sides and the floor joists are tied into this sill and the sill on the original house. It appears that the roof of this porch is supported on top of the 1x3 boards that make up the floor. The first question pretty much has an obvious answer but I jest need the reassurance for myself and my wife- do I need to scrap what is there and replace the foundation with a full foundation and second - should it be safe to support the roof with 4x4 on the ground while building the foundation. The roof is a nearly flat roof and only covers the 12 x 6 room. If pictures are needed I can try to get some posted. Thanks in advance!

Welcome to the forums! There may be more than one plan of attack for this, but before we go there, post a few pictures on a site such as photobucket.com and copy/paste the HTML code to your reply post. That way we can see what you see and give better advice. Be sure to post pix of all the parts you have questions on.

Larry