Concrete fence posts.

[Wireboy]

I posted a topic reference cutting up a concrete base and garage demolition last month.

Further to that job is that once the garage is down, I need to install fences between my self and the neighbour to the side. There have never been fences there before as there was my garage and there's.

They knocked down there garage years ago but left there concrete base intact and never installed fences.

There is a 6 inch gap between his garage base and mine. The boundry is easily identified as this 6 inch gap.

I need to put concrete fence posts down this edge. 4 posts in total.

How wide do the holes need to be to place the concrete post in and get enough Postcrete around it?

I have recently purchased post hole diggers from Screw fix which does a great job but the round hole is only 6-7 inches wide. Is that wide enough?

 

[JohnD]

the purpose of the concrete in a post hole is only to fill the gap between the post and the surrounding firm earth, and to prevent spot-loads. It is a positive disadvantage to dig an enormous hole, loosening the earth and needing a barrowful of concrete.

As your posts are going between two concrete slabs you can presumably pack concrete between the posts and the slabs, which will prevent them blowing over. posts need very little support "sideways" along the length of the fence. 6" will be fine although you might find chunks of rubble in the way. In which case look for a post spade, which has a very narrow blade. Consider filling the gap between the slabs with a few inches of concrete to reduce weeds and it may look neater.

 

[Wireboy]

Cheers John

I have 4 posts to do.

Post 1 will be going against his base but my base would have been ripped up at that point so should be quite easy.

Post 2 is going in between our bases and will probably be a pain as I have only a 6 inch gap and hardcore of 2 bases to get through.

Post 3 will have my base still there but the neighbours will have stopped (it was never as long as my base) so that should be ok. I'm still expecting to hit hardcore on all three.

Post 4 is a "3 way" or "T" piece post. This is going right at the back where there has never been bases and should just be soft loose soil. Hopefully no problems there.

So in all that, only post 2 will be between 2 bases.

How deep should the concrete be in the hole?

Do I fill the hole up all the way to ground level or do I stop short and fill the rest with soil?

Cheers.

 

[JohnD]

IMO it looks neatest in a garden if either you stop the concrete an inch or two below ground level, or if you knock up a bit of shuttering so that the only exposed concrete seen at or above soil level is a round or square collar round the post. A ragged uneven hole filled with concrete right up to ground level looks very shabby, I think.

There is a slight advantage to trowelling it smooth with a slight fall away from the post to help water run off and reduce frost damage.

The depth of concrete should be right to the bottom of the hole, and up to, or just above or below, ground level.

If the hole is very untidy and large, you can pack damp half-bricks or large clean stones into the depth of concrete as your pour and tamp it town, provided they are free of mud, dirt or especially plaster, and are fully encased in the concrete. this economises on your mix and also enables you to wedge your post so that it does not lean.

Cover the top of the pour with plastic or some other impermeable cover, if it is kept fully wet for a couple of weeks it will cure harder, stronger and more frost-resistant. Do not let the posts wobble in this time. Especially protect it from hot drying sun or winds for a couple of weeks; more if you can manage it. Once it is allowed to dry it will turn from dark grey to near-white and you can never restart the wet curing process. Underground concrete is especially hard and strong because it often stays wet for many years and this improves the cure.