Deck Stair Footer Below Frost Line

by Zach
(New Jersey)

Hello all,

I have been looking for a good way to construct the footer for deck stairs. My research has lead me to believe that it is not necessary but a good idea to have the footer of your deck stairs go below the frost line. I have been looking around trying to find a good way to accomplish what I want and haven't found a solution that I like.

I had idea to use a 4x6 and 2 concrete foundations. I would dig two holes near the ends of the lowest stair. install 2 concrete footers and use simpson strong tie concrete to wood connectors (PB44Z). I would then install a 4x6 across the supports. I would follow that up with attaching the stringers to the 4x6 with joist hangers. I have drawn this out in sketchup and attached a snip of the model.

I just want to know what you guys think. Any feedback good or bad would be much appreciated.

Some added details:
Total stair width is 50"
Railings will be over the steps and the bottom post will bolt down to the top of the stair (into the 4x6 below the tread).
Total rise of steps is ~36"
Using Timbertech Azek deck boards which require spacing of 10" (or some other form of support)
Frost line where I am at is 36"