Post holes

[kjacko]

Guys,
gotta put up a new fence up and will be using either 8ft x 4"x4" concrete or wooden posts (notched so the panels slide into the grooves). Sunken 2ft into the ground, which is mostly clay.
Because its clay and a bugger to shift i bought ths:
http://www.machinemart.co.uk/shop/product/details/060230664?da=1&TC=SRC-post+hole

It's a 6" auger so makes a hole with approx. 1" space all around the post.
Question is, will that be good enough space to pour postcrete into and set good enough so that it won't move?
I'm hoping i don't need to dig a hole that will require more space all around the post so that i have to use a full bag of postcrete and it will take me ages to dig. I get that it will probably be more secure, but given its a clay bed, surely it won't be prone to much movement?

Advice appreciated, thanks.

 

[r896neo]

1 inch is too little you really need 3'' all around the post minimum. Postcrete is very weak because there is no stone in it so it is prone to fracturing. The first high wind could shake the post and send cracks through the post crete leaving the post rocking a little.

 

[ImayKnow]

Once you have bored the hole you can use a small spade to square the sides off and open it up to give more clearance for your concrete filling. As per other poster I would use a proper concrete mix to get a strong fixing in the ground, tamp it down well to ensure no air pockets remain.

 

[kjacko]

aaaw crap! really?

I can't dig such a narrow hole 2ft deep. I'd need to go out and buy another spade for postholes costing about £40+

This sucks.

 

[wrathkeg]

the problem I've found with using a spade is that you then have to somehow get the soil out of a 2 foot deep hole.

so if you're going to spend £40 you might consider something like this which I've found really useful:

http://www.toolstation.com/shop/Roughneck+Post+Hole+Digger/p55706

 

[freddiemercurystwin]

This sucks.

Welcome to DIY fencing!

 

[kjacko]

Guys i have a load of leftover sand/stone mix that was used for my conservatory foundations. I guess i just need to buy some bags of cement to mix with.
Is this better than postcrete and can i use a dry mix?
I'm guessing the benefit of postcrete is that it sets very quickly?

 

[ImayKnow]

aaaw crap! really?

I can't dig such a narrow hole 2ft deep. I'd need to go out and buy another spade for postholes costing about £40+

This sucks.

RUBBISH!!

A cheap small spade from b&q etc is only about 7" wide. You could even borrow one from a neighbour.

Bore the hole as originally advised and use the spade to square of the hole. As you remove soil from the sides you will be able to use the spade to lift it from the hole. Christ it's only two foot deep and pre bored for you!

I have dug them 2.5 feet deep with just a spade.

Come on, MAN UP !!

 

[r896neo]

I go feral and just clean the crap out of the bottom with my hands once i'm past about 1 foot. Post hole diggers are useless for actually digging they are only really for scooping out loosen material.

Postcrete is fine but i prefer not to use it for 6ft high exposed fences as it just isn;t as strong.

Strength isn't acutally that important its more important that its firm but my original reply about fractures is why strength is worth considering.

Sometimes its easiest to set your first and last post with postcrete because it will be hard in 20 mins and then you can run a line between them to set the others.

 

[wrathkeg]

for me the way that works best (on a combination of heavy clay and buried boulders) is to use a spade to get started, then use a digging bar like this which smashes through pretty much everything, including toes

http://www.toolstation.com/shop/Lan...ools/Roughneck Digging Bar/d130/sd2822/p48155

and have a helper keep using the post hole digger to empty the hole at regular intervals. that way I don't have to rummage around on my hands and knees.

but i didn't really want to suggest that method to someone who had already invested in an auger

 

[kjacko]

Rights, thanks for the replies fellas.
I used the big corkscrew auger and its really good for getting depth. Then as advised i used a 5" spade to square off and slice down the walls, so i have pretty much a 10" x 10" square hole, 2ft deep now, which gives 3" clearance all around the post.
The problem with a spade into clay is that i didn't have the horizontal clearance to bring it out, so i went 'feral' and hand shifted all the churned up stuff at the bottom. It wasn't really loose, by the time i'd got it in my hands it was really sticky, heavy and compressed into big lumps.
The land slopes from the woods down towards our property, and the fence goes across the slope not down with it. Just need to try and get my levels right and the ground is pretty uneven from one end to the other (about 36ft)
Any tips on getting the posts in at the right depth considering the uneveness of the ground?
Imagine picking the whole existing fence up and pivoting one end about 4ft, so that the other end stays where it is, well that's what i'm doing, to even out our perimeter, but i'm totally replacing the old knackered fencing at the same time. Need to keep the existing one up as long as possible to avoid the animals getting out and other from the woods getting in.
Not a completely straightforward job tbh.

 

[wrathkeg]

when you say uneveness of the ground I'm not sure if you mean an overall slope so you want a sloping fence or just bumps and hollows between posts.

as r896neo suggested, you could set your first and last post then run a string line to give you the height for the others. that way the slope would be gradual across the whole run. if the slope is very gradual you can keep the tops of a small number of posts level with each other using a straight edge and spirit level, then step down for the next few then down again etc. it looks better if the steps are equal obviously.

when installing the posts if one intermediate post needs raising up a bit you could put some gravel or well compacted hardcore in the bottom of the hole or a shovel or so of concrete if you are doing concrete posts.

this might help especially if you're doing concrete posts

http://www.pavingexpert.com/featur02.htm

doesn't talk about slopes though.

 

[kjacko]

when you say uneveness of the ground I'm not sure if you mean an overall slope so you want a sloping fence or just bumps and hollows between posts.

Basically the ground along which the fence will run is quite undulating with bumps and hollows. I'm hoping for a straight and level fence height all the way along. I don't actually know (yet) if the end posts are on the same level or not. Putting a string line between them won't show me their level, and I'm not sure how accurate it would be to carefully offer up a spirit level to this string line to see how level it actually is. Is there a better method?
I won't be using gravel boards at all, just 6ftx6ft panels inserted between slotted posts. I guess i could rake out the ground below where the panels will sit, but i don't want to half bury any of them due to the uneven ground.

Lol, I'm trying NOT to overthink this, but i often underthink things and come a cropper half way through a project.

Your continued advise is very much appreciated.

 

[wrathkeg]

search for "string line level" and/or "water level". these can tell you whether things are level across long distances. dunno how the pros do it.

personally I wouldn't put wood panels in contact with the ground, but that might be just me. if you used concrete gravel boards you could but of course there would be the extra expense.

 

[kjacko]

Yeah, sadly budget plays a major factor here, so no gravel boards i'm afraid.
We only intend on staying in the house for another 3-4 years, i'm sure the panels will last that long. I will do what i can to protect the underneath of them. Maybe even a strip of dpc on the bottom baton.