Building A Low Profile Deck?

I am building a deck approx 20 x 20'. The door going into the house is only 3-4" above grade, so I have trenched the 2 x 8" x 10' joists into the ground about 5" at 16" O.C. with 2 x 10" x 10' beams attached to post footings (concrete sono tubes 48" below grade) located 10' and 20' away from the house respectively. I live in Toronto, Ontario, Canada. I now want to attach the ledger to the house. Will frost heave push the deck up and eventually tear the ledger away from the house?