Garage Slab Failure

slab crack

The garage slab of this 40 +- year old home has cracked and settled approximately 6″ towards the house.

My assumption is that this failure is due to a combination of improper compaction at backfill and moisture entering the ground beneath the slab.

The driveway slopes to the slab and the surface water disappears from there.  Homes built in this era has no footing or foundation wall between the garage door. The driveway drainage is going straight to beneath the slab. Combined with improper compaction, the slab has cracked. It is not known what is supporting the slab at this time. There could be a void between slab and sub-grade.

Hergert Seattle Bellevue Everett Washington