Which fence posts shall i use?

[mac3582]

Hi,

I need some advice if anyone can help.

I am replacing some fence panels at the back of my garden. there is a building about 3 feet behind it so I am using 6 foot panels with 2 foot trellis on top to try and hide as much as possible. I would really like to put the posts 3 feet in the ground but nobody does 11ft posts near where I live. the company I am buying the panels from do 12ft posts but they are 47mm x 75mm.
my question is, am I better off using 47mm x 75mm and doing 3 feet deep, or am better off using either 75mm x 75mm or 100mm x 100mm and doing them 2 feet deep.

thanks

 

[r896neo]

47mm x 75mm is not a post. If it was steel it may be ok but timber those dimensions would be really weak and you couldn't make a concrete post that long and thin as it would be far too brittle.

Someone trying to pass off these as a post should not be trusted.

3m timber posts (always use 100mmx100 posts unless its for trelis) should be easy enough to get and they will be plenty.

3m concrete posts are monsters. Because they are so long they have to make them bigger in section so they can be 6''x4'' or even 7''x5'' and they are super heavy. Even 2 men will just about manoevure them.

3 foot into the ground is excessive, 2 feet will be plenty. Once a post is concreted 2 feet deep it will sooner snap off in a heavy wind than the post be rocked loose.

 

[Porque223]

my question is, am I better off using 47mm x 75mm and doing 3 feet deep, or am better off using either 75mm x 75mm or 100mm x 100mm and doing them 2 feet deep.

thanks

That depends on the wood properties and the soil properties. The wood properties are more easily found out than the soil properties.
The wood to a certain depth, and the soil, are equally strong when there is an equal chance of the post snapping or the post uprooting.
Check what others have done in your area.

In the US any fence over 6' is usually considered "a spite fence" but Neighbor Law over here may be different.

 

[mac3582]

thanks for the replies.
the 47mm x 75mm were just in the timber section and I assumed I could use them as posts.
I was leaning towards the 100mm posts but just needed some assurance, so ill go with those.
thanks for the help