Three years ago, I built a detached garage with an apartment above. Of course, “garage” is a euphemism for “shop.” With a limited budget, I wasn’t planning to hire other contractors and I wanted ways to save both labor and money, starting with the foundation. Living in Connecticut, I’ve long been jealous of builders in the South, where the shallow frostline allows for building on slabs with thickened edges. Here, I was looking at excavating the perimeter down to at least 42 inches below grade, pouring a footing, laying a concrete block wall to above grade, then evenly compacting the...

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