Fence post holes - too big.

[AMS1]

Hello

I've just replaced 5 fence posts in the back garden as the original posts were very old and had rotted, bringing the fence panels down in high winds.

Obviously I dug out the original concrete boulders housing the old fence posts, and they took up quite a bit of room (and bags of postcrete). This was just a quick repair to appease the neighbour, but I'm hoping to build a new, higher fence next year when funds will be hopefully improved.

The problem will be when I come to dig out the concrete blocks housing these new fence posts I've just put in ... the holes will obviously be bigger again as I will have to dig slightly further out again. I'm worried they're going to be less holes and more craters.

My question is - would I be able to backfill some of the holes to make them more manageable? I've read that holes should be roughly 3 times the width of the post, but these holes are a lot wider than that, at least at the top.

I was wondering if I could put something in the holes about the right dimensions (tubing or a bucket or something) and fill the gap around with soil, leave it to harden and then remove the bucket (or whatever). Would this be feasible or would the soil around the 'frame' be too weak, and thus making the fence posts (when I eventually put them in and add the concrete) too vulnerable to moving around?

Or is it just a ridiculous idea?

 

[r896neo]

You cant do it because the earth you backfill will never be firm enough. You must dig post holes in original virgin earth.

The solution is to move them by using a half panel at the start. Obviously your corner posts will have to be in the same spot so you'll need to just have huge holes for them.

So, say your posts are 6 feet apart you have holes at 6,12,18,24 then unless you very lucky and your garden is a perfect division of 6 feet your last panel is probably a cut and is for example 4 feet. So your holes are 6,12,18,24 and 28. Simply start with the 4 foot cut so your holes are 4,10,16,22,28.

Of course if your cut panel Is very close to 6 feet you will have to have a half panel cut at both ends to get the majority of the posts to miss the old holes.

Last advice would be to leave the old concrete in there. Just cut the posts off at ground level, digging out the old concrete will loosen all the soil badly.

 

[AMS1]

You cant do it because the earth you backfill will never be firm enough. You must dig post holes in original virgin earth.

The solution is to move them by using a half panel at the start. Obviously your corner posts will have to be in the same spot so you'll need to just have huge holes for them.

So, say your posts are 6 feet apart you have holes at 6,12,18,24 then unless you very lucky and your garden is a perfect division of 6 feet your last panel is probably a cut and is for example 4 feet. So your holes are 6,12,18,24 and 28. Simply start with the 4 foot cut so your holes are 4,10,16,22,28.

Of course if your cut panel Is very close to 6 feet you will have to have a half panel cut at both ends to get the majority of the posts to miss the old holes.

Last advice would be to leave the old concrete in there. Just cut the posts off at ground level, digging out the old concrete will loosen all the soil badly.

Fair enough - I did wonder about the integrity of the soil if I attempted to backfill - I'm guessing soil takes longer than one thinks to compact enough.

When I do my fence next year I want to use individual pickets (or boards or whatever they're called). I've got a year to worry about the planning of it .

Unless of course these posts I've just put in don't last the year .

Thank you for the advice.

 

[r896neo]

Same principle applies and its even easier using boards as the posts don't need to be exactly 6 feet apart.

 

[AMS1]

Can I just ask one tiny extra question (about fence design)?

On the Wickes' site it gives a tip stating: "A continuous, flat run of timber fencing is most susceptible to wind damage. If possible, incorporate 90-degree returns at the ends." What do they mean by 90 degree returns?

"Even a slight change of angle between panels, or a zig-zag pattern, will provide a valuable bracing effect." What do they mean by this? I'm interested in the physics of it all (that, and the fact that I don't want the fence to blow down a few months after putting it up).

 

[Ian H]

With a 90 degree bend it is supported both ways.

Lean a book against another book in a straight line then at 90degrees to each other and they can't fall over.

 

[Doggit]

If you hire a medium size breaker then you can get the concrete out without enlarging the holes. And if you decide to move the posts, then you could hire a petrol driven hole borer, and the holes will be small enough to get away with Postcrete, which will be a quick and easy job. When you put the new posts in, paint bitumen where the posts come out of the ground, and then they won't rot next time. Earth moves around them over time, and the water sitting around the bottom of the post, is the most common cause of failure.

Your original design worked well enough till the posts rotted, so you don't need to worry about Wickes advice; you got it right the first time.

 

[Tigercubrider]

Use a post hole digger.
Much easier than a spade and maybe £25 to buy.
It allows you to dig deep but narrow holes

 

[AMS1]

Thank you for the responses. I've actually got a post hole digger, but I didn't know about painting the bottom of the posts which come out of the ground in bitumen. I've got a year now to think about (and save up for!) a taller fence which I want to build from scratch (this existing fence is just a short one).

My back garden slopes up a bit along the back (I would say by around 50cm). If the height restriction is 6 foot, presumably this means that I'll need to cut the fence boards which will go along the back, and those which will travel up the side slope, so that the fence is uniformly 6 foot in height everywhere, and not 6 foot + 50cm(ish) along the back?

 

[Ian H]

If your making your own panels from 1.8mtr feather edge you could follow the ground level and have 6ft all along.

 

[Doggit]

Although you set the wooden posts in cement, the cement shrinks fractionally, and can allow water to settle in around the post. You can often deal with this by putting bricks or rocks at the bottom of the hole, and this allows any water to drain away, but if the earth then moves over the top of the concrete with the garden getting mown etc, and then settles around the post, then they can rot there, so painting the bottom of the post with bitumen, can help protect them.

 

[RrogerD]

Hi,
I appreciate that this thread is over 2 years old. I came across it via a search due to a similar issue that I have.
The hole around the old concrete lump is massive! It all about a 70cm in diameter. If I do as suggested and backfill with rocks etc and then Postcrete I'm in an even worse position when the rots next time.
I guess that I could cut a panel in half and put in two posts, one either side of the old but that would certainly mess up the look of the full fence run.
Any ideas?
Is it possible to bore out the old post from the conc lump and slot the new post in perhaps?

 

[RrogerD]

In the pic above, I've added a splint to the old post and rotted stub just to put fence back in place for the moment.

 

[Tigercubrider]

What I would is temporarily support the fence with a couple of long bits of timber to the ground, and remove the old post. You should be able to drive a metal crowbar/scaff pole into the rotten socket and lever the concrete out by rocking it. Try to get it out in one piece without disturbing too much soil.

Then possibly use the old concrete and some bricks to infill the large hole along with some concrete but leave the area for the post alone (an area that resembles a bucket in size.

Then I would either :
Replace the whole post with a new concrete one
Or
Use a "repair spur" that is intended to sit alongside the broken wooden one.
In normal use, the hole is dug next to the broken wooden post and the short repair spur bolted alongside.

Once either method is done, infill with concrete. Personally, postcrete is easier. Add half the amount, water, and the other half.

 

[RrogerD]

Thanks Tigercubrider.

Your suggestion is definitely a possibility. My concern though is that if I backfill the large hole with rock, bricks and or concrete then the next time that the post rots, I've an even larger hole and lump of concrete to try and remove.

I've read somewhere, possibly on an American site, that it is possible to fit post 'wings' or ribs. I understand these are affixed to the base of the post, or at least the section underground and then simply back-filled with soil on top. I guess that the 'wings' provide a larger surface area and so less resistant to movement in looser ground.

Has anyone any experience of these in the uk? Any ideas where I might get some? (I guess nowhere at the moment with our friend Covid)