Short fence posts hole depth

[mrwood777]

Hi all,

I have a quick question that I hope you can help with as I can't find quite the right answer online.

I am building a raised bed at the rear of the garden which will also act as a divider/step to an elevated part of the garden. I plan to use 3*3 treated fence posts and then board across the front of them to a height of 20".

With such a low height how deep a hole do you recommend for the posts? The soil is very hard and clay based so quite supporting. The posts will be at 2.4m centres and will not be holding too much soil behind them.

Also, I'm planning to use postcrete and wondered if I can use it in wet soil as it's been raining here for a while.

Thanks in advance

 

[HERTS P&D]

Use 100mm x 100mm posts and have 1.2m apart.

Andy

 

[mrwood777]

Thanks, any reason for that or just extra support? The area behind is very firm as it is tied together by roots

Any help with the questions?