CONCRETE BASE - ADVICE GRATEFULLY RECEIVED

I've decided to start a project that will need a level concrete base to support it. The concrete will be 8 feet by 8 feet by 12 inches in depth, it will also be 8 inches in height above the ground. Why 12 inches in depth? The project will need a base that is absolutely flat and level and one that will be resistant to moving over the years.
So, the question is how deep will the Footings need to be.?? My idea would be 6 inches of hard core/brick rubble, 2 inches of soft sand on top, then Visqueen plastic for damp proofing, and a final pouring of 12 inches of concrete. But I would be grateful for any advice or ideas for improvement.

 

Hi Jiffy,Not that heavy really. But the base must be substantial enough not to move or crack over the years, give no vibrations when moving around on it, and I might be using 6 inch bolts to secure something onto it which again must not move or vibrate.

 

Hi Pete,............not sure. Should it be??? Mesh or Rebar could be used, I suppose, to stop the any chance of the base moving or cracking.

 

Mine's on a concrete raft and so far so good. My surrounding soil is mostly sand but in the area of the intended base which is near the House it is compressed clay, sand and other things!!

 

D'at is why me asking?????

 

I've been tussling with the idea of this project ever since I managed to get the Bell's Palsy....due to being bored, I guess, and the location has been a real headache due to me not wanting to give up an inch of garden.
. The first location [Plan A] was so tight and filled with problems but I stuck with it for a week. Then I woke up and thought "Naaah", and decided with a heavy heart that Plan B would have to do which mean the loss of some of the middle garden path, some of the Lawn border, and, worst of all, loss of the Clematis Trellis Entrance, plus a little bit of lawn.
I went to bed, work up the following morning and thought "Naaah" and went onto Plan C. Plan C means losing 6 feet of lawn, most of the "Kitchen Border"and that's it. The Kitchen Border doesn't contain any valued plants to be honest so Plan C it is.