building on foundation of posts

has anyone built on posts where the ground is hopelessly uneven. i am wanting to put up another building on very uneven ground where it is impossible to get any machineary into.
i can only go about 12' wide but as much as 40-50' long, I have lots of 6-10" cedar logs that can be buried a couple feet in the ground and won't have to worry about decay or bugs. was thinking using it for arts and crafts shop..

Building on top of posts is easy. Throw 'em in the ground, chalkline a level line and cut 'em to level. Attach your floor joists and continue from there.

But, I might suggest you think more about how you're going to get the posts attached to the ground. There's two reasons to drive posts into the ground — when the ground can't support weight or is subject to liquefaction (marsh, reclaimed land like San Francisco, etc) or when you are expecting moment forces (bending, like you'd get in an underground greenhouse from the earth's weight on the walls). Otherwise, it's a good idea to keep 'dry feet' — cedar or not. You can set the posts on concrete blocks, poured concrete footings, or a hard rock like granite (you'll need to carve the bottom of the post to conform to the rock's contour). My old log cabin is built on roundwood posts that sit on granite blocks, but I mostly use the cheap concrete blocks that hold 4x4/6's from Home Depot for sheds and smaller structures.

It might help to see a diagram of how you're planning to build this structure. Your foundation / footing design depends a lot on your structural strategy (post & beam, stick, log cabin, etc) since the forces in the posts will vary.

"What exactly do you mean by "hopelessly uneven"? I say this because you might be surprised on how level you can make something.

Lets say for instance that your building is 12 feet wide and changes 4 feet from left to right in that short amount of space. If you dig 6 feet back into the hillside to a depth of two feet, and fill six feet on the lower slope with 2 feet of soil, you will have a perfectly flat area for your building, and have only had to dig out half of it. It is called cut and fill.

You might also be surprised where you can put an excavator. I worked a mountainside all last fall where it was so steep, in places I had to hook my bucket into a stump and drag myself up...hoping the stump held to the ground the whole time. And goodness knows it is impossible to tip a bulldozer over. Both can be rented of course.

But don't get me wrong, building on post foundations is really easy too as Kyle explained so well.

My grandfather did, on the NC coast.  It was a nearly perfect design for a home in frequent hurricane flooding.  Unfortunately, I he died when I was 10, so I did not learn from him.  If you get a chance to visit Holden Beach, NC, I am sure you will get several ideas.  He was one of the first to do it, and it has come a long way since.  Most all homes there now are at least a story up, off the ground, with drive under parking.  If that can be done as the standard in a coastal flood zone, doing a lower version would likely present fewer issues and cost.  

thanks for the input, I have been busy, and my helpers disappeard last week after getting paid for finishing first building. trying to figure out how to buy a used excavator on limited budget. i guess i will dig or drill post holes pour in some concrete and set the posts. i came across some 4'-5' 10" x 2"+ pr wood scrap from dock building company. was thinking of bolting three of them together for some of the posts. i have a bunch of foot long 3/8" all thread with nuts and washers that came out of a dumpster.  i gotta love dumpster diving from industrial buinesses

My camp is going up on posts, more specifically, reclaimed telephone pole. I have gotten prices from almost free to $2 to $3 dollars a foot. I also planned to keep it up high enough to keeps the structure out of a deep snowfall and provide me with someplace to park a canoe, quad ect on a bed of 1 1/4 gravel which I'll extend out 10 feet or so in all directions she there's no " tinder" under the structure.  At that height, I'll probably need some diagonal cross members to stiffen it up. The telephone poles I looked at were pressure treated ( at one time ) but could probably use a coat of creosote   When you get started, please post some photos.  TY. Larry

Cross bracing is always worthwhile for anything over about 4 feet tall.
Creosote is not a good product to use in the environment, you maybe better to look at encasing the poles at ground level where the moisture content changes, thats usually the point were rotting takes place if it is going to happen.
A constant moisture level in the timber will protect it, assuming the timber is not prone to rotting in the first place.