John was building a new fence, and he wants it to stand 8 1/2 feet above ground level. To make sure it stays?

Question

John was building a new fence, and he wants it to stand 8 1/2 feet above ground level. To make sure it stays?

Answer 1

If you are asking how deep it should be buried, then the answer is approximately 12 inches (with a footing), 18 inches without

Answer 2

John should examine the surface he is working on, and if it is soil, then the moisture level is very important.  He should also look carefully at the climate of the area, and if he is dealing with frost in the ground, he will have to consider digging below the frost level to prevent frost heave of his fence posts in late winter periods.

The material composition, weight and construction of his fence are also  factors since it will be exposed to wind, particularly when soil conditions are wet and there is less support for structures, trees included.  *(attention to trees is also important so that damage to the fence from falling limbs can be avoided)

John also needs to check the survey of the lot line carefully,..... even the best constructed fences on neighbouring properties seem to have a habit of coming down.

These are a few things that would influence the staying power of John's fence.