timber related but not woodwork

[Tonyz]

needing to post some permapine posts into sandy ground to support a fence.
posts are 100-125mm and need to be out of ground 1200. What depth should be buried into sandy clay base.

[Wrongwayfirst]

My thumb rule is 1/3 in 2/3 out so 400mm. Sandy clay sounds lovely I have clay clay which is rock hard and in need of a crowbar when dry, sticks to everything when wet and makes you taller by the step, but it does have a sweet spot about 3 days after rain where it comes off the shovel like peat moss slabs. But I digress.
My hole diameter is double post plus post, so a 100mm square post gets sunk in a 300mm square hole.
filled with concrete.

It is your prerogative you can go deeper, wider, you can dig the sides so they flare out at the bottom 300 top and 400 bottom. But the above is how my holes are done.

cheers

[AlexS]

Recommendation by Wrongwayfirst is pretty much spot on. We used the same for installing river gauges, 1/3 in ground, 2/3 out, in whatever soil except sand. It may be worth hiring a hand held post hole digger.

[auscab]

Recommendation by Wrongwayfirst is pretty much spot on. We used the same for installing river gauges, 1/3 in ground, 2/3 out, in whatever soil except sand. It may be worth hiring a hand held post hole digger.

What do you for sand ? Make it deeper ?

[Tonyz]

What do you for sand ? Make it deeper ?

:D already done 3 @ 900deep holes, luckily have a petrol auger but a hand held hole spade needs to be borrowed.
Beaudy though 400 saves a lot of extra digging.

[malb]

Beaudy though 400 saves a lot of extra digging.

My interpretation, 1200 out of ground, 1/3 in, 2/3 out suggests an 1800 post set 600 deep, not 400.

[Tonyz]

My interpretation, 1200 out of ground, 1/3 in, 2/3 out suggests an 1800 post set 600 deep, not 400.

:D :doh:

[Wrongwayfirst]

My interpretation, 1200 out of ground, 1/3 in, 2/3 out suggests an 1800 post set 600 deep, not 400.

No you know why I also say measure twice cut once:U:U

[rustynail]

Strainer posts= 2400 long. Line posts=1800 or 2000 long. Longer posts for soft ground ie sandy. "Any post hole under 600mm is just a divert." That was what we were told when I was a kid working with fencing contractors in the far west of NSW.

[AlexS]

What do you for sand ? Make it deeper ?
Drive it as far as possible with a post driver, then dig the hole around it 600 deep (at least), drive it further if possible, pour concrete to try to prevent scouring around it, and possibly install a downstream brace.

[auscab]

I saw a new paling fence erected once . About six foot high and right down the long side of a property. The boundary fence of a fish and chip shop in a sea side town . Not sure how deep they put the posts in but a week later after a typical big blow from the S/W the whole thing was pushed over.

We did these with that petrol digger . Then screwed two horizontal hardwood rails all along. I think they were 2.1 posts with roughly 850 to 900 in the black sandy ground . Nice and easy to dig but to much hard work at that length. Never again. The next similar job like that I was happy to pay for the two guys and their tractor for one long day to drill and ram the posts in. They were near lots of trees as well.

The one good thing about that driveway fence was no trees for the post hole digger to catch the roots.
Hanging onto that digger when it catches roots is something you learn to do in a way that doesn't take you with it pretty quick after it happens once .

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