Good day everyone, looking to get some input and advice. I will be removing and rebuilding the structure (framing and sheathing) under an addition that was put on the back of my home. Been living here for a little over a year and now that its summer its time to correct a few issues.

The main issue is the sill plate rots out because it does not sit on the outer edge of a poured concrete pad or foundation. I understand basic building principles, how the sill plate and bottom of the sheathing/exterior sheathing must be a minimum of 6″ above grade to avoid these moisture/rot issues. Unfortunately, I don’t see many good options to correct the issue as I cannot raise the foundation/concrete pad.

My thought was to build a one row high concrete block stem wall around the perimeter and attack the new pressure treated sill plate to this with j-bolts and frame around the supporting metal columns. My desired end-state is to have a small tool and outside equipment storage room beneath the added on sun-room and side it to match the addition (vinyl siding) but be free of rot and moisture issues. 

Note: The poured concrete around the current structure does have pitch away from the house so water does not accumulate there.