Setting concrete fence posts

Discussion in 'Builders' Talk' started by DIYDave., Mar 5, 2014.

  1. DIYDave.

    DIYDave. Screwfix Select

    Hi all
    Hopefully at the weekend I will be putting up a few 7 foot, concrete posts, 12" gravel boards, 4 foot panels

    I know this question has been asked\answered a thousand times and generates almost as many variations but just want a simple clarification please......If possible !

    Decided against using Postcrete - seems pricy for a bit of sand and cement but realise you're paying for convenience (plus I guess a whole lot of expensive additives)

    Seems 2nd easiest option is "all in ballast" and add cement in a 5 - 1 ratio. Add water but keep a dryish, stiff mix

    Will dig down 2 feet, drop in posts, level, prop with some hardcore, concrete, tamp down, check levels, drop in panels, prop if needed with some timber

    All sound ok guys ?

    Any need for adding plasticiser to the mix ? I guess not
    Also no clear verdict on a dry mix then either leave overnight or sprinkle with water or just adding the water before chucking in the hole

    Would appreciate your thoughts as ever

    PS - Will also sort out my gate over the w/end using the concrete screws as recommended recently - thanks
     
  2. Sean_ork

    Sean_ork Screwfix Select

    if you've got a quarry close they'll probably do a ready mix - just add cement/water to suit - it'll cost next to nothing if you can collect - or a ton bag from a merchants

    your plan sounds OK - there's a 100 ways to do this - nice sloppy mix, not dry - treat yourself to a MiniMix
     
  3. Phil the Paver

    Phil the Paver Screwfix Select

    Having done fencing for more then 30 years, I will tell you the only way to do it :), all in ballast mix at 6.1, NO water at all, the moisture from the ballast is enough.

    As you say 2' deep hole, but only about 2"/3" wider then the post on all side, put a couple of inches of the concrete in the bottom of the hole, post in then start filling with the concrete every 6" compact the concrete down really well ( I have a proper fencing Graffter) but a sturdy piece of 2" x 2" timber will do, if you have done it right you will have trouble moving the post straight away.
     
  4. DIYDave.

    DIYDave. Screwfix Select

    Cheers Sean
    Was planning on getting sacks of ballast from B&Q as near to me, with a discount about 1.40 a sack so cheap

    When you say a ready mix from a quarry - just add cement\water.........That's what I was planning on doing with the above anyway

    From my understanding (may be not quite right) the ballast is an "all in" mix - so contains aggregate and sand, then I'm adding cement and water so this equals concrete

    5-1 ratio sounds about right to you Sean ? Plasticiser Y / N ?

    And you say a nice sloppy mix then.......I just though that a stiff mix would support the posts better whilst setting

    As we both said, loads of ways around this and I guess that if you do this on a regular basis, then you will have your own, preferred method, tried and tested
     
  5. Sean_ork

    Sean_ork Screwfix Select

    yep just add cement/water - we call it consand up here

    ratio sounds fine - doesn't need to be accurate, no point adding anything other than water and cement

    sloppy mix will run and fill any little voids - don't bother trying to dig a nice tidy regular shaped hole
     
  6. DIYDave.

    DIYDave. Screwfix Select

    Thanks Phil for sharing your 30 years + of knowledge - much appreciated

    Have borrowed a decent (trenching I think it's called) spade from my brother. I gave him a hand last year building his decking and we both agreed that my post holes were superb, neat and tidy with vertical sides and not over large. So I've had a bit of practice !

    Ok so a 6-1 mix and no water. Seen the sacks of ballast at the weekend and although stored inside B&Q, noticed how wet the mix was, plus I guess the ground is damp this time of the year
    Yep will tamp down the concrete, got some spare timber posts that I can use

    Have been reading up on this and having trouble deciding which method to go for, ie dry mix (Phil) versus wet mix (Sean)

    Is it just down to personal preference or is there a more scientific reason for dry / wet mix (don't want to start another debate like the current PVA saga on the plastering thread) ;)
     
  7. Sean_ork

    Sean_ork Screwfix Select

    do what Phill says - but either way your fence won't fall over ;)
     
  8. Phil the Paver

    Phil the Paver Screwfix Select

    With a dry mix you can put the fence up as you go, ie: post in, gravel board, panel, post and so on, with a wet mix you will have a post that may aswell be set in jelly, you will end up with bracing bits of timber all over the place.

    One thing to remember is that the concrete isn't holding the post in the ground, the depth is doing that, you could in theory just fill the hole with ballast and it would hold, but over the course of time it would wash away with rain fall, so the cement is just to bind it, putting it in dry it will take on moisture from the ground and set firm enough to stop it washing away.
     
  9. Sean_ork

    Sean_ork Screwfix Select

    if it's a proper trenching spade you'll not find it much use - see if you can borrow a set of spoons

    my wet mix argument would be that you have control of the moisture content
     
  10. Phil the Paver

    Phil the Paver Screwfix Select

    [quote="Sean_ork,

    my wet mix argument would be that you have control of the moisture content[/quote]

    Sean for what purpose, this isn't concrete that has any bearing on strength or load. its a fence post.:)
     
  11. Sean_ork

    Sean_ork Screwfix Select

    it's to ensure there aren't any dry friable voids within the mix
     
  12. Phil the Paver

    Phil the Paver Screwfix Select


    LOL, Sean behave, it's a fence post, not a muti story carpark. ;)
     
  13. Sean_ork

    Sean_ork Screwfix Select

    we build strong round these parts ......... or it'll blow away

    do what Phil says Mr D (but only because he's bigger than me)
     
  14. Phil the Paver

    Phil the Paver Screwfix Select

    LOL, you have a sense of humor, I'll give you that. :p
     
  15. DIYDave.

    DIYDave. Screwfix Select

    The spade is "like" this one......http://www.screwfix.com/p/spear-jackson-newcastle-all-steel-drainer-16/38521
    My brother got it for digging post holes, really nice to use, long but slim blade so the holes don't end up too large and sharp

    Yeah those spoons look good Sean, can always hire a set for the weekend but will probably just dig then scoop out by hand, dig, scoop, etc
    That's the difference when your doing work for yourself, time versus money isn't the deciding factor so if things take a little longer, then you just drink more cups of coffee during the day

    I to was thinking that a dry mix (although I was going to add a little water) would support the posts better whilst setting and less props, also lets you complete the fence as you go

    But.... the more you read up (dam internet) some peeps say the dry mix doesn't always cure fully, you get pockets of sandy material amongst set concrete, may not be enough moisture in the material and ground, etc. So for a diyer like me, its sometimes really hard to make an informed decision and have the confidence to go ahead with it - too many conflicting methods

    quote="Sean_ork,
    my wet mix argument would be that you have control of the moisture content[/quote]

    As for the above, would it help if I PVA'd the surrounding soil first.........................................Only joking.....................:p
     
  16. Sean_ork

    Sean_ork Screwfix Select

    I've been using that trick for months, I've been rumbled
     
  17. Phil the Paver

    Phil the Paver Screwfix Select

    As for the above, would it help if I PVA'd the surrounding soil first.........................................Only joking.....................:p[/quote]


    Dry pockets will not make the slightest difference, though I haven't seen any on fencing I've replace, as I said above depth is holding the post.

    Your spade will be ok for digging, though the angle of the handle may get in the way when compacting the concrete.

    I use and own one of these.


    http://www.amazon.co.uk/gp/aw/d/B0044TPTKO
     
  18. Mike Green

    Mike Green New Member

    Just stumbled upon this thread by accident, if anyone is following for advice, please, please, I implore you to ignore Phil the Pavers advice, whilst he may have been putting up fences on and off for 30 years, I have been a fencing specialist for 15 years and have read with mouth wide open in horror, Wet Mix concrete, not dry, there is a process called hydration which starts the chemical reaction to turn cement into concrete, 4/5 in 1 cement to ballast ratio, use a slump test to check you have everything mixed properly, hole should be approx 30% in ground to out of ground, 6’ post out of ground should be 2’ in ground, stand post should have approx the same width of the post surrounded each way by the same amount of concrete, 4” post should be 12” hole with post to middle, whilst your fence may not be a multi story car park, it needs strength to stop it blowing away in the wind, a 6’ wide panel is extremely weight bearing in the mildestof gusts, a gale will just push it over. If in any doubt, consult a specialist, not an odd-jobber.
     
  19. Isitreally

    Isitreally Super Member


    This is a joke yes!!!.

    Use a slump test on fence post concrete. :p:p:p

    A fencing specialist. ???

    While a totally dry mix might not be right, who going to the trouble of gauging the mix to the point of a slump test on a fence post. :rolleyes::rolleyes::rolleyes:
     
    Jord86 likes this.
  20. goldenboy

    goldenboy Super Member

    I do a bit of fencing here and there.

    Mainly to get a bit fitter.

    I dig a hole about the right depth.

    I stick the post in

    I put some water in

    I pour the postmix in

    I put a level on the post.

    And repeat.

    None of my fences have blown down yet.
     

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