How to decide on on-grade or frost-proof for wood shed foundation

I'm planning on building a wood-shed near my house, 9' x 12', to hold 4 cords of wood for winter heating. We get so much winter rain (PNW) that a wood shed is essential for keep dry fire wood.

I'm unsure what type of foundation I should use. The plan is to build a simple 'post and beam' style, open sided, metal sheathed shed style roof. The roof's high side will be to the south, which is also our weather exposed side. Our frost depth is 18 inches.

The sources I've read don't agree, some say go frost free (concrete pier footings below frost level) some say on-grade is fine. I'd like to build a shed to last a couple of decades, but if an on-grade foundation will suffice, I'd happily avoid digging 2 foot holes and dropping all the cash for cement and quick-tubes.

What would you advise?

Kirk Hockin : Raised compacted fill, floating slab- large overhangs ! Big Al

Kirk Hockin wrote:

What would you advise?

based on your desire to have it last a few decades, i would suggest 2 ft hole and concrete. sona tubes arent always necessary if you can dig the hole only as wide as necessary to fit the posts.
i agree with Al on the large overhangs too.