Another heaving problem under a deck

[Hookmaster]

I have a walkout that exits under a 3-season porch. There is a deck off the porch that runs the rest of the length of the house. Right now there are old patio blocks (8"x16") under the porch that heave up in the spring and then resettle. Under the deck is dirt/grass. My AC unit sits here and it tips some with the heaving. I plan on adding gutters to the porch to keep water away from this area but I think the main reason it heaves is my backyard is the flood plain of a creek. It never floods into my yard but the water table is high. Would it work to put a free standing deck on footings to keep this area more stable? Any other ideas?

[sparcebag]

I'd put it on posts,the posts dug down in minnetonka area min. 42" And either a (cookie) round concrete 2 inch thich like patio block or concrete base.Even the AC unit could be kept from moving if you dug down 42" and filled with 3/4" or larger gravel,then used a flat base on top of gravel for unit.

[Hookmaster]

Why posts rather than footings? Just easier?

[sparcebag]

Yes less digging,less concrete so you could buy it premixed in bags.

[boatfixer]

One thing to consider when back filling if you use treated posts, is to use something that will drain well such as pea rock or sand. Like Sparcebag said, just make sure you go below the frost line and you should have no problems.