Using Postcrete

[billy bookcase]

I need to replace some broken fence-posts installed insufficiently deep, given the ease of digging them out, by a previous occupant. I have a fence post augur which can easily go down two feet with a long bar to dislodge stones etc. Postcrete has been suggested in addition.

Looking at the (laughable) videos the theory of Postcrete seems to be digging a really wide hole filling it half with water with the post positioned pouring in the Postcrete and forming a wide round Postcrete slab at the bottom of the hole into which the post is held upright for 10 ins until it sets. After which the hole is backfield.

So totally unsuitable for use with neat holes made with a post hole augur presumably.

bb

[Tricky Dicky]

Most professional fence installs I have seen the post holes have been deep rather than wide. Filling wide holes with postcrete is going to be very expensive. If you are erecting timber posts then I would simply use postcrete for what it is good at namely fast setting to get your posts situated quickly. If the posts are going into soil I would then add further normal concrete using perhaps forms to neatly raise the concrete level above the soil as it is at air/soil interface that rot appears.

Richard

[newshound]

Personally I would auger the hole to two feet, put in a couple of inches of dry postcrete at the bottom, put in the post and hold it centred before adding more dry postcrete around it, compacting it as well as possible with something like a length of rebar, tamp it down thoroughly with a lump hammer and block of wood when the postcrete reaches the surface (topping up as necessary), and *then* add water.

[Chris Hogg]

+1

Adverts for Postcrete are intended to make you use a lot, hence the big holes!

Make sure the concrete eventually ends up an inch or so above the level of the surrounding soil, like flaunching, to throw off rainwater. If necessary, after getting the post in place and the Postcrete set, use an ordinary sand/cement mix to finish it off.

Concrete posts don't rot, or, cheaper, concrete repair spurs, which allow you to use the uppers of old timber posts that haven't rotted.

[alan_m]

What be your method of securing a post into an auger hole? It cannot be by pouring in some concrete because you seem to have already dismissed the equivalent method using postcrete.

In my experience postcrete does work well with post holes only 3 to 4 inches wider (on all sides) than a post. Using postcrete doesn't stop the use of broken brick etc. to wedge the post in place before adding the postcrete. The water can also be added after the dry postcrete has been added to the hole and then tamped down with something like an iron bar, which also puts holes in the postcrete to allow the top applied water to penetrate.

It seen a lot of fencing companies use postcrete because it allows them to build the fence in the sequence install post, install gravel board, dig hole for next post, install panel, install post....... The quick setting of the postcrete means that the posts are stable within a very short time.

[John Rumm]

Last time I used it was with neat holes dug with a post hole tool and a graft:

The holes were 2' deep. I placed a bit of broken slab in the bottom so that the post was not in contact with soil, half filled with water, and poured in a bag of postcrete. Added a little more water of required, and then tamped it with a length of timber. Made sure the post was held upright and let it go off. I then flaunched up the top with some additional (ordinary) concrete once the postcrete was set.

[billy bookcase]

Thanks for the explanation,

You followed the standard method of pouring in the water then the postcrete. Newshound and posters on other sites suggest pouring in dry postcrete and then adding water.

What I'm wondering is why it isn't possible to mix the postcrete in a bucket and pour that in, tamping down as you go ? Obviously exact ratios would need to determined beforehand using paper cups etc, But that isn't mentioned anywhere. Ten minutes drying time would seem more than sufficient for this

I need to keep the holes as narrow as possible in order to avoid disturbing established plants either in terms off having to dig them out or causing too much root damage

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[Chris Green]

Chris Hogg [e-mail] wrote: [snip various bits of good advice]

Wooden posts generally work better (in terms of longevity) *without* any concrete. We have 9 acres of land divided up for grazing with electric tape on wooden posts. I thus have a fairly steady job of replacing the posts if/when they fail and learn what works and what doesn't work.

I have *some* posts which were originally knocked into the ground more than 20 years ago and, when I moved them just recently, were still very sound. These were not machined round ones, they were simpler 'stripped bark' ones, not beautiful but certainly effective!

[The Natural Philosopher]

I put in some garden posts some years back using various grades of pressure treated timber straight into DEEP holes (dug slowly with a garden TROWEL to about 1.5m). Holes then backfilled and tamped down HARD.

They will last as long as the pressure treating does and postcrete would not have improved them.

Some of them with less well treated quarter round timber have simply rotted below ground level

I cant see that except in the case of very slender posts with no lateral area to resist being pushed over, that encasing in concrete adds anything much at all. Its a quick (and expensive) way to e,g use a digger to make a bloody great hole and not bother to back fill it

[The Natural Philosopher]

Yes, its a low labour high cost way to do it. You gain very little stability and i am of the opinion that encasing wood in a concrete sheath doesn't stop it rotting at all - there is so to speak no damp proof course, and water will wick through the concrete and up the post and rot at the base no matter what.

Advice I was given years ago and experience shows that a good treated timber post is fine in bare soil.

A badly/un- treated post will rot no matter what.

[Peter Johnson]

Presumably the people who make videos don't own an auger.

[Another John]

That's wrong - ask Postcrete, Inc!

By the time you've mixed it, it will be half-set!

Postcrete is brilliant, imho, in certain situations. But if I had your

2' augur (and, infinitely more important, your evident strength!) I'd use properly treated posts, a stone in the bottom to encourage drainage, and then just 1" inch gravel, tamped hard (as TNP has mentioned). Needless to say, you need to centre, and square, and level, the posts precisely -- but you absolutely have to do that with Postcrete anyway (at least you can just about extract gravel, before it's tamped too hard, if things go pear-shaped.

As John Rumm said, I'd finish off the top few inches with 'flaunching', to cast rainwater away from the hole. You could use Postcrete for that, as long as you work quick and neat! :-)

Good luck! Take your time, mind!

John

[Tim Lamb]

Oak lasts well. Better with a bit of rot proofing. The post and rail fencing to our by-pass is still sound after 45 years! Although a bit degraded by Sunlight. I have mentioned the preservative in here before.. smells of Mothballs and makes the wood non-flammable. For field strainer posts I would use a mix of rubble and small stones. Intermediate posts sledge hammered into a hole opened up with a crowbar.

[Adam Funk]

Maybe they've changed the instructions, but when I used it about 15 years ago, I put the post in place, poured the dry mix around it, propped the post up plumb and then used a watering can to gently pour water into the mix.

[billy bookcase]

The 4"dia augur "could" go down to 3ft although your knuckles would be scraping the ground. The trick is to only turn it once or twice, pull it out, and scrape off all the soil, and then go again. It was bought years ago for round posts. These are 4in sq. You do need a long bar however to clear any obstructions it meets on the way.

This is just to keep the neighbours happy basically, without spending a fortune on it. Rather than it lasting 50 years.

bb

[alan_m]

The oak posts I dug out of my parents garden years ago were around 50 years old. Judging by what came out they were just placed in a hole and back-filled with earth BUT the bit underground was tapered. The width of the post at the bottom of the hole was approx twice that of the width at the ground level.

[John Rumm]

It will probably work, but you may not hydrate all of the mix as well. Its a non critical application, so it will not make much difference in practice - so long as it sets it is not going to matter if it achieves full strength.

It is, but the whole idea is to make it very simple. No pre-mixing required - stick a hose in the hole for a bit, or chuck a bucket of water in, empty in the bag of dry mix (which is hence lighter and easier to handle), quick prod with a stick, make sure the post is upright, and then leave it to do its thing.

As you can see from the photo, my holes were only about 6 inchs wide with a 4" post.

[John Rumm]

I found with a 24" hole, there was not quite enough in one bag to fill it to a level where you could do the flaunching (which really needs to be just above ground level), so doing all the flaunching in one hit later was easier.

[Brian]

Used correctly, it seems to work fine. I had some fence posts and panels replaced after a previous storm, they survived the latest one. We lost some other panels etc but the posts repaired with postcrete are fine.

[newshound]

Even dry bits are going to hydrate from the ground pretty quickly!