The size of hole - The size of hole required is dependent on the height of the post it
will be supporting. Generally, bury one quarter of the post to provide a firm foundation.
If for example, your finished fence needs to be 6 feet (1.8 m) high, use 8 feet (2.4m) posts.
One quarter of 8 feet is 2 feet. Therefore dig a 2 feet deep hole to take the 8 feet high post
which will give 6 feet above the ground as the visible post. Make sure the hole is wide enough
to support hardcore and concrete around the bottom and sides of the post. There is a tool available
called a post hole auger, which can be hired to help with the digging of the hole (see Hire Shops)
The auger is twisted as it drives into the ground, removing and loosening the ground. It looks
like a large corkscrew on a very long handle. You will need to stop every so often to pull out
the auger in order to remove the contents of the hole before proceeding again until the correct
depth has been reached. The post hole auger is less effective in very stony ground.
Securing the posts - Once you have reached the correct depth, you are ready to secure
the post into position. Fill the base of the hole with a bedding of hardcore, this will enable
the post to have some drainage away from the base of the post (vital if the post is wooden, to
prevent rotting at the base). Support the post into position with battens and stakes. If the
post is concrete, stabalise its position with guy ropes. Check the vertical position of the
post with a spirit level, before filling the hole with concrete - use a mixture of 1:2:3 = cement:sand:aggregate.
Push the end of a batten into the hole to make sure there are no air pockets and there is a
firm even mix all around the base. When the hole has been filled, it is worth building the
concrete up, just above ground level, and slope it away from the post. This will deter water
running down the post and into the base of the post. The concrete should take approximately
one week to harden. It is advisable to leave the supports around the post or other temporary
struts to secure the positioning against any movement during this time.
Securing end posts for chain link fencing - It is essential to anchor the end posts
securely, particularly when using chain link fencing. Chain link fencing requires the end posts
to resist the tension of the straining wires at the top and bottom of the fencing. A notched
end post is advised as this can be supported by a pre-cast strut. Secure the notched end post
in the ground.
Dig a channel along the line of the fence, taking it a little further along
from the position of the bottom of the strut. Make the channel approximately 18 inches (450mm)
deep. Fill the bottom of the channel with hardcore and wedge a brick under the strut to force
the strut tightly into the notched end post. Fill the channel with concrete and allow the area
to thoroughly harden, before attempting to attach the straining wires. Use a special bolt and
cleat to adjust the tension. When putting on the wire netting, bolt a stretcher bar to the
cleats. Threadle galvanised wire through the pre-drilled holes and use it to tie the straining
wire to the posts.
