[Closed] How much postcrete do I need?

I've always found I need 1 bag minimum, or 2 for a proper job per post. I think it depends on the ground - Nice ground where you can make a perfect round hole then you need less. The scree mixed with rubble that passes for my garden, 2 bags per post to the point where a mixer makes more sense than postcrete.

Last time I used about a bag and a half per post. 1 will be ‘ok’, but the more the better I say. I would of used 2 bags but got too knackered digging the holes.

If you ram some old bricks and rocks around the bottom of the post, then the postcrete helps bind it into a bigger, heavier more stable lump then 1 bag should be OK - the last set of posts I did like this are still standing 20 years later.

I've recently put some 8' posts in, one bag didn't feel anywhere near enough, 1½-2 bags per post was much better.

I never trust blokes on the internet when there’s a data sheet available! All the information you need is in the TECH sheet on the TP website.

A repair spur is 4”, seeing as you’re using a 1.2m spur I’m assuming that’s a 6’/1.8m fence panel, so you’ll want at least 600mm in the ground. The tech sheet says 1 and 3/4 bags per post to fill a 250mm by 600mm post hole. I’d buy 4 bags.

That seems to chime with what the blokes on the internet are saying above.

Leaving aside the data sheet there's another human and environmental factor here...

Can YOU dig a decent size and shape post hole? If your holes are oversized or you have to widen them to remove baby head sized lumps of flint 8" down (grrrr!) then in reality that data sheet is going to leave you light. I've done a fair bit of fencing and concreting in of posts since we last moved 15 years ago and definitely better at it (and have removed a lot of the mega rocks) now than when I started and use a lot less materials but I am still no match for the excellent guy we've used to do larger projects who uses considerably less than me as he digs much better holes.

That's not to detract from goldfish's advice but just bear in mind the data sheet was probably written for a tradesman with hole digging experience in "average" conditions.

Perhaps depends on the ground as well. If your ground is soft then you might need to make a bigger lump of concrete (i.e. a bigger hole) to give it enough ground to bind onto. However if (like at my house) the ground is mostly rocks anyway then you only need a slim hole and you're using concrete to bind onto the rocks that are already held solid in there. Of course if you have lots of rocks you could lob some back in before you pour runny postcrete in.

I'm fencing next weekend. The actual digging is going to be the hardest bit by far. 8" rocks are the easy ones. Some needed two people to lift after they were dug out. I gave them away, then I realised at current 'rockery stone' prices we probably had £500 worth.

Allow 500kg per post...

One bag per post should be more than enough. I’ve recently done quite a bit and even with variable size holes that was the average!
Hope this helps.

About 1 per hole. But I use a post hole digger in mostly non-rocky ground. This gives a clean/neat hole. It could easily be more in rocky ground, but then you can add some of the rocks back as big aggregate.

The true cost of doing a 'cheap' job with only 1 bag of postcrete far exceeds the extra £12 for two more bags. It will be a triple factor ball ache to have to go back and fix if 1 isn't enough.
Its difficult to think of a scenario when your parents fence is too strong. And if you really don't need them all, take them back.

As above - I found it's about 3/4 of a bag for a decent job, so two bags and an extra £5 to avoid having to do a bad one is a good deal.

1 to 1.5 bags each. The work is in the prep etc, scrimping on postcrete is a false economy in my view.