Hi again,

Some source (not an engineer) told us that the garage slab may not be
structural. In the south they use slab foundation thus the slab is what the
house sits on. We are in the northwest. The foundation is foundation wall
and the studs sit on the foundation concrete wall not the slab. Slab is just
to cover the garage floor. The slab is somehow not well connected to the
foundation walls. Our foundation walls were poured early October but the
slab was poured one month later after the framing and roof were built up.

With this info we went to check again in the evening. The crack IS higher
and the steel ruler sits across it bit like a seesaw. With 3' (half of the
6' ruler) sitting on one side of the crack, the other end is about 1/4"
about the floor. We extrapolate this 1/4" from 3' to 11' (half of the garage
width), we get about 0.9". That would be the amount the far end slab has
settled. We checked where the foundation wall and slab meet all around the
garage. There is NO sign that there is shift between the slab and the wall.
It looks more like there has been some clay soil heaving near the front
middle part of the slab so the crack open up and is a bit higher than either
side - the soil under the gravel is clay, and the house has gone through
freezing temperatures of Dec and Jan without garage door in place. The three
2" long cracks on top edge of foundation wall are probably not uncommon. If
the walls had settled down together with the slab at one corner for 1" or
so, we'd have larger cracks in wall.

We know the builder put rebar in the slab. He told us he put rebar
everywhe driveway and patio.

So it doesn't sound as bad as it did at the beginning.