Bricks, Masonry, Asphalt and Concrete - Garage Addition Concern!

Im adding on to my garage 22 x 22 and im going to do it as a pole style addition,my concern is that I have started digging up the top soil and there are alot of roots from a big maple tree I had cut down a year ago,the ground seems spongey and ive already dug down 12 inches,my question is,if I build up the ground with 12 inches of gravel before the concrete goes in will this work ok?

Thanks Mike

how high is the water table in your area?, if it is not too high 12 in of compacted gravel should work but you might want to check the organic content of the soil first, just send a sample to your local county extension office to have it tested. if the organic content is too high you will need to dig further down. as it probably will compact to much over time.
if the water table is very high you will need a vapor barrier over the gravel to keep from leaching through the concrete when finished.

life begins when the kids leave home and the dog dies.