Post Hole Boring

[STAR]

I have just recently redesigned my small acreage block and decided to rip up my old fences and put in some new ones.

However, this time, as age is catching up I did not bore the holes for the corner posts by a hand held auger i got a friend in who had a bobcat with a post hole borer attachment.

When I put the posts in I found the soil difficult to ram because the borer had broken up the soil into a small sieve size and it was impossible to ram down.

I then had to remove as much soil as I could from around the posts and then concrete them in to get the compaction I needed. Is this a normal occurrence with a post hole borer or was it just because the soil and clay was so dry that it was impossible to get the compaction necessary.

Putting the Postcrete in was not really a problem for me but wondering why the soil did not compact has me thinking. Is this a one off, and has anybody else come across this also.

[STAR]

39 Views and no replies.

Guess I did the right thing for putting Postcrete in to the post hole as compacting the soil was not going to work,.

ps.

The concrete has done the trick, the posts are nice and compacted, do not know why the original soil did not compact.

Although, all ends well that ends well.

[Buzza]

Sounds like your soil is of a sandy nature Star. The mix will do for that for sure. If the soil has a little bit of clay or a lot of clay, and bucket of water poured onto the refilled hole usually has it settling in a day or two. I think the mix you put in is the best way for any soil actually.

[johnc]

Usually by just ramming a small amount at a time you get all the compaction you need, even in sandy stuff. Shovel full and ram with the back of the bar (blunt end) until firm then another shovel full. If a bit worried mix a bit of cement with the soil, then ram, then allow ground moisture to set the mix.

Unless the soil was near dust I would have thought you should have been OK.

[STAR]

Buzza and John. I think you may just be right. I filled the hole with water and added the post crete. Success

I think the missing ingredient may well have been moisture,.

[DavidG]

Small layers, pounded with the spud bar until it rings is the usual method.
The grain size does not matter but if it is too dry then a little water added to the process will help the compaction.

Bit of ready mixed concrete sure beats an hour or so of pounding, though.
At least with my back.:U

[Different]

Around here we have sandy soil and lots of Sandstone and Ironstone I like to ram some soil the a layer of roch and smash the crap out of it then another layer of soil.
Concrete is not a great solution as the post often shrinks with age and then flops about in the concrete and you cant tighten the post if it gets loose like you can in soil and expensive if you have a lot to do.



ross

[joe greiner]

I have to agree with Ross (Different) that concrete is not a perfect solution, especially when placed dry and watered to accomplish hydration. A timber post encased in concrete will be subject to rot, and prone to faster degradation.

Better to place aggregate about 6" (150mm) under the post, and fill the rest of the hole with aggregate, pounded to strengthen and stabilise. This allows water to drain from around the post, and reduces rot.

Joe (Civil & structural engineer, BTW)

[twisted_timber]

I have a vacant block I will be placing a basic post and wire fence around. I have a heap of used permapine posts on another nearby property. The soil is quite hard, of a limestone rock/clay nature. I intend on digging the holes by hand with a post hole auger. What depth would it be adviseable to sink the posts to, 3ft...is that overkill, or would 2 be enough? The posts themselves are not overly long, so it will be a relatively low fence, a visual more than a practical one as there is no fence at the moment.

[Vernonv]

Hi Twisted_Timber and welcome.
We have heavy clay soils and for non-gate posts I would normally go down at least 2 foot (600mm) and I always ram the backfill heavily. Gate posts normally need to be deeper.

[twisted_timber]

Hi Twisted_Timber and welcome.
We have heavy clay soils and for non-gate posts I would normally go down at least 2 foot (600mm) and I always ram the backfill heavily. Gate posts normally need to be deeper.

Thanks for that. I was hoping 2ft would be okay, gives me a little higher fence line. I should have enough longer posts for the strain taking corner posts and gate posts which I'll drop to 1 metre roughly as you suggested. Only 5 acres, so not too big.

Cheers
Mark

[Gigitt]

Things to consider about your rural fence...

The higher the fence the harder it is to hop over - for yourself when you need to go to the other side and the gate is too far, and other animals like kangaroos, horses, cows, goats, deer and dogs etc.
NB: pigs like to go under the fence as well as kangaroos if they can't get over!

A higher fence around your home will keep your dogs in.

General farm strainer fencing is done with 165cm length Star posts and droppers.
Each star post is actually driven into the ground 45cm leaving a 120cm high fence - your fence baseline.
You can lower the fence by not laying the top wire which is usually Barb.
For a higher fence you will need to go the 180cm Star posts.

My Neighbour gave me these tips:
If you are sinking timber strainers and gate posts, sink the fattest you can.
Use at least 1ft diameter trunks, they may be heavy but will last for a very very long time. Even when they start to rot or termites and ants eat the middle out a thick post will still hold.
Length of strainer/gate post to cut is 7ft4in, 8ft if you want a higher post. You can always cut the top off after you have sunk it in.

If you pyramid the tops of wooden posts the water will run off and the center will take longer to rot.

Use your old Post holes. Saves you digging a new hole, and will keep your boundary the same.

Use timber from the area or within 15km. Generally this local timber will rot slower than foreign trucked in similar species.

Use White Box or Ironbark for strainer/gate posts and stays. Anything else will only last a couple of years in the ground.

If you fell your own posts, get the bark off asap. If you leave Iron bark on the trunk even after a day it is harder to get off. After a week it is like concrete.

Very costly to sink boundary posts with concrete.
Use concrete around the house and with metal posts. It will last longer and look neater.
If a concrete set post needs fixing it is harder to get out of the ground. Most posts if anything need aligning vertical after some years - especially gate posts. Easy to dig on one side, realign and then repack the base. You cannot do this with a concrete set post.

Hope this helps you and others.