A couple of years ago I purchased a property in the country with an old mobile home and a detached garage on it. The garage is approx 20' x 30' with a concrete floor and a cinderblock foundation around it. The 2 x 8 sill plate for the garage is rotted so I'm going to replace it. At the spots where the sill plate has rotted away I can see down through the cinder block and there is no footing underneath it. I've driven a piece of rebar down through the openings in the block to confirm that there's noting underneath it but dirt. The mobile home that I live in is the same way. It has a concrete block foundation around the perimeter but no footing underneath it. Both the mobile home and the garage are more then 40 years old and in that time they dont seem to have had any structural problems other then the sill plate rot in the garage.
My question is.............was it once a an acceptable practice to build a block foundation without a footing ? Is there anything I should do to improve my garages foundation when I replace the sill plate............other then pressure treated lumber ?