Postcrete/Concrete Questions

Hello all,

Having tried to look for alternatives (see my 2 recent unanswered posts), I have come to the conclusion that I need to 'bite the bullet' and use concrete or postcrete to fix posts. I am happy with digging the holes etc. but I have never worked with postcrete or concrete. Despite having read literally hundreds of threads on this topic, I am after some clarification please.

I have a number of 8 foot fence posts to set (2 foot in hole and 6 above gl)

1. I am told that postcrete is not particularly suitable for 6 foot posts as it is prone to cracking and, in any event, has very little ballast in it for strength. Views?

2. If I were to use postcrete, the MI suggests water in hole first then postcrete. However, advice on here has suggested postcrete first, tamped down then watered. Which is better?

3. Assuming I use concrete, I would need to mix it myself. Three questions on this:

(a) Is a 5:1 ratio of ballast to cement correct?

(b) Wet or dry mix? If wet mixing, how much water for the above ratio?

(c) If a dry mix placed in hole and tamped down, how much water on top?

Sorry to be thick but,as I said, I have never mixed concrete before. I am more than willing to give it a go (especially as it works out much cheaper than bags of postcrete) albeit I will have to mix it by hand.

Thanks in advance.

B

B

I used postcrete on my fence run, this was with some large posts, 2 foot in the ground.

The trick is to use the correct method. I put some water in the hole first and added all the mix and compacted it in with a bit of timber to pack it in tight all around the post. There was sufficient ballast to pack it tight. I then added more water to this until I had used the correct ammount for the number of bags I had used, so that the lot would "go off" properly. I managed to get all of my posts up and in the ground in an afternoon, having dug the holes already. I was then able to crack on and get all of the rails up the next day, completing my weekends work. I then added the feather boards through the evenings of the next few days.

Postcrete is a quick and easy solution to what can be a difficult problem.

I was able to do the whole lot so quickly, i didn't need all of the supports and saved the time from mixing all the concrete by hand. Yes it does cost more than mixing your own, but it is also a lot easier, unless you are concrete competent.

This was on 15 concrete fence posts over a run of 21m of fence.

EDIT: I would have commented on your foam post but had never even seen the stuff before, the other option might be to put concrete sockets in the ground, in which you fix your posts using dry sand to hold them in place. I have never done this personally, but I know it is possible and certainly works for road traffic signs...

Personally I wouldn't use post/con/crete.

See https://www.youtube.com/watch?v=g-juMYulXHI. You also need to set your posts deeper. You should bury at least a third of the post.

Belboz
For DIY i have mixed Concrete, Mortar and used Postcrete.
Being tight for money, I once considered using Concrete (which I considered cheaper) rather than Postcrete to put in 8 fence posts.

However (I think) I correctly chose to use postcrete for teh following reasons:
1) If you use concrete you have to mix it which takes time. And if you mix too much (for the hole you have dug) then you have to throw some away, and if you mix not enough then you have to mix more. Loss of lots of time and effort.

2) My main reason>>> Postcrete is fast setting Concrete. So when you pour it into the hole it sets very quickly. So the post is then nicely set place. And you will not (easily) knock post out of place (which you will do with slow setting concrete) whilst you are setting up next post.

3) If you do not use all the bags of Postcrete, you can take the spare ones back to the shop and so your garage is not full of half used bags of Ballast and Cement.

4) Going back to money. I did wonder about making my own postcrete. So I compared prices (wickes):
where 1 x Extra Rapid Cement £15.49 + 5 x balast £1.55 = £3.87 a bag
or Postcrete = £4.50 a bag
So I decided that I rather pay the extra 63p per bag of Postcrete than lose the time it takes me to mix the Cement and Balast.

So my recommendation is - buy lots of bags of postcrete, use them and take the unused back to the shop. No recommendation on how to use postcrete as I followed the instructions on the side (I think were put some water in hole, put in postcrete. tap down, put in rest of water).

SFK

jblessing,
He has a very nice method in the Video.

And thank you for the reminder, I put three feet into the ground for my six foot fence.

Also, some recommend that you do not use the (70mm by 70mm) fence post, but instead use the larger (100mm by 100mm) fence posts. Their claim is that because the 100mm by 100mm has twice the wood it takes longer to rot and longer before you have to replace.

SFK

Thanks to all who have replied thus far.

Andy - no worries re the foam - I hadn't seen it before either hence why I asked for views/experiences. Seems like no-one has used it!!

Watched the video clip posted by jblessing. Interesting and worth a watch but not entirely suited to my needs.

I have a fair few to fix and plenty of time so time is not a factor. Likewise, no wastage as there will be many holes to fill with any mix I make up and the posts will all be fixed prior to using concrete/postcrete so no hassle with levelling etc.

It seems that postcrete will work fine from what you have all said so that may be the way I go. FYI - a bag of postcrete is now £6 from Wickes so the cost saving by using self-mixed concrete (ballast and cement) is now a lot more. If I decide to go with postcrete then I will need a significant number of bags!!

Thanks for the tip regarding the depth. I was under the impression that 1/4 of the post is buried but it seems you are suggesting 1/3rd. Guess I will need to order 10 feet posts and cut them down to 9s rather than use 8 feet as planned (The fence height must be maximum)

Once again, many thanks for all the replies and advice thus far.

Very much appreciated.

B

Balboa,
Great to hear.

Note that the price I said for the postcrete i think was correct as i based it on their current 4 for price of 3 deal as I presumed you would need more than four bags.

However for the fast setting cement to make your own postcrete I used their higher non-deal price as you have to buy 5 bags (and so 25bags of ballast).

Sfk

I am a lady and with the assistance of my daughter we installed 65ft of Jacksons fencing with postcrete. I had 8ft posts with 2ft in the ground and it has not moved, unlike my neighbours that wobbles in the wind!! We put the required amount of water in the hole, using a stick with a marker to know how much we needed and then added the dry postcrete.

Tigger90 - thanks for that - nice to know.

SFK - didn't notice the 3 for 4 deal at Wickes but have since looked at B&Q who are doing a deal on 5 bags for £4.56 each. That works out 6p less discount a bag but B&Q is a lot closer to me than Wickes so would use more than that in fuel cost (especially with the extra weight)

Unless I hear to the contrary, I will go with the postcrete rather than mix my own and see how I get on.

Thanks again to one and all.

B

2 foot in the ground is plenty for a 6ft fence.

I have just finished a fence with 18 posts. I use 2 1/2 bags of postcrete for a 2 foot hole so overall that is probably 200 quid in postcrete.

I prefer to use concrete but i get it delivered semi-dry and then add some water after the posts are packed in well. 1.2 cubic metres of semi dry concrete was 120 quid.
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I've used both concrete and postcrete, both are good but postcrete will cost a lot more even at the offer price.

Best way (imo) is to make a 5 or 6-1 mix of ballast/cement and make it just damp, fill hole and then tamp down hard with a bit of 3x2 or similar.

I have never used a post longer than 8' for a 6' fence and so far have never had one fail.

Thanks neo and 2trowels but one stupid question...

What is the best way to achieve getting the mix damp or semi-dry??

Thanks again

B

Mixing semidry concrete yourself is a real pain. It just doesn't mix well and constantly sticks to the drum.

If mixing yourself rather than getting it delivered mix it as dry as possible but so that it still mixes well. It will still hold up well even if its quite wet, as long as its stiff enough.

Get a price for delivered stuff and then price up the materials needed to make it yourself. You may be surprised at the small extra cost of getting it readymix.

As its semidry its just delivered on a tipper rather than an expensive dedicated mixer truck.

For example 1 cubic metre of concrete requires

1.2t of gravel
.65t of sand

Or say 1t of sand 1t of gravel - maybe 60 including delivery

300kg cement - 12 bags - 48 quid