How to use Postcrete

34 Comments

  1. Kevin Nolan

    Can I use postcrete to install sleepers as fence posts with the dimensions 2400 x 200 x 100
    buried 600 into the ground with a 300 diameter round hole? If so how many bags do you suggest?

    Reply
    • Olga Waterhouse

      For your particular use we would suggest 4 bags per post, this will ensure the hole is completely filled with Postcrete, and should
      reduce the chances of the posts ‘slipping’ over time under the weight of the sleepers and any soil they may be retaining.

      Reply
  2. j wilson

    I am installing a 240cm ×10cm fencepost.
    how much postcrete do i use?

    Reply
    • Olga Waterhouse

      With a 240cm x 10cm post typically 60cm will be below the ground, the width of the hole would be 30cm.
      2 bags of Postcrete will fill the hole approximately half full, once the post is level you can backfill the hole and compact it.

      Reply
  3. Keith

    I am installing a 5cm square post how deep and how big an opening

    Reply
    • Olga Waterhouse

      Typically for a 5cm (2.5 inch) post the minimum hole width would be 15cm (6 inches), so you would need a narrow trenching spade or a post hole / split shovel. The depth is dependent on the height of the fence (post) required above ground, as a guide a minimum of 1/3 of the above ground height should be below ground e.g. if the post has to be 180cm (6ft) above the ground 60cm (2ft) should be below the ground.

      Reply
  4. C Jordan

    How long do you have to wait before you can hammer nails in postcrete?

    Reply
    • C Jordan

      I mean how long before you can hammer nails into posts set in postcrete?

      Reply
      • Olga Waterhouse

        Good question, we suggest a panel can be hung in as little as 10 minutes using Postcrete (weather permitting of course).
        There is a good technique for nailing in to a vertical post, if you start the nail as normal with a couple of light taps and then hold a second hammer or in fact anything heavy (a brick works well for example) in constant contact with the opposite face of the post to where you are nailing, this simple action will reduce the vibrations or wobble in long posts and make your job of nailing the panel or panel clips far easier with less force needing to be exerted through the post with the hammer… Alternatively you can screw the clips or panels to the post, this way you can take them down if you ever need to without damaging them.

        Reply
  5. Alan CARDWELL

    I’m using 3-inch posts with 6ft above ground and 2ft below. How wide should the hole be, please?

    Reply
    • Olga Waterhouse

      Thank you for the question, typically the width of the hole should be three times the width of the post; so in your example the hole would need to be 9″x9″ (22.5cm x 22.5cm). This may be a little narrow to dig with a standard spade so if you have to do lots of posts it could be worth investing in a ‘split shovel’ or narrow trenching spade.

      Reply
  6. Russ

    Can I drill a fixing into post crete to secure deck post foot plate as I have used post crete to create strong flat base on uneven soft ground.
    Thanks

    Reply
    • Blue Circle Products

      Thank you for your question.

      Although we are aware of Postcrete being successfully drilled for fixings, Postcrete has been designed and formulated specifically for the erection of fencing and smaller gate posts to be embedded within the material; as such, we would not consider it to be the best option for your particular application.

      Assuming speed is one of your primary concerns, best practice would be to use our Extra Rapid Cement (https://tarmac-bluecircle.co.uk/product/extra-rapid-cement/) mixed with an all in ballast. The lager aggregate of the ballast (typically upto 20mm) reduces the chance of cracks forming while drilling the holes and/or tightening the fixing(s). Concrete made using Extra Rapid Cement will provide an excellent long term durable solution in your particular application while still gaining strength considerably faster than a concrete produced with a conventional cement.

      I hope this information helps.

      Kind regards

      Reply
  7. Dave

    Hello, I am building a kids climbing fort and using 10cm x 10cm x 360cm posts. The hole to bury them in is 30cm x 30cm x 120cm.
    How many bags to you suggest per post this seeing as these are the supporting legs of the climbing frame.
    I take it if takes 4 bags you fill the hole with 4xWater then all 4 bags at once, you don’t wait for one bag to set before layering in the next bag on top?
    Also do you recommend filling the holes to the top for extra support or is back filling the top 1/3 of the hole with soil okay?
    Thank you

    Reply
    • Blue Circle Products

      As best practice we would not suggest using Postcrete for a child’s climbing frame as there is no guaranteed compressive strength – it is ideal for supporting fence posts and smaller gateposts.

      We would suggest using your High Strength Concrete instead which is guaranteed 40N, again ready to use just add water but is not fast setting and normally takes 2-3 hours to set. Based on measurements given you would need just over 11 bags per hole.

      Kind regards

      Reply
      • David Steen

        Can you help me with amounts I will need please?? I am building a kids swing and slide set in the garden with pegs securing the bottom of the wooden frames to the floor. There with be 6 mounts to the floor. The holes for the pegs it asks for 15cm diameter circular hole 30 cm deep. They are small ancher pegs for the wood to screw to. How much High Strength Concrete (40N) would I need?

        Reply
        • Blue Circle Products

          Hi David,

          Thank you for your enquiry, If you choose the ‘Blue Circle High Strength Concrete (40N)’ on our website you are taken to https://tarmac-bluecircle.co.uk/product/high-strength-concrete-40n/ where there is a handy volume calculator for the product. Based on your measurements you will require just under half a bag per hole (so three in total for your six “mounting points”).

          Reply
  8. Alex Knight

    Would postcrete be ideal for setting 150mm x 150mm green oak posts into the ground for a gazebo?

    Reply
  9. Howard

    I’m building a slightly raised deck over an old rockery to put a greenhouse on. How deep a hole should I dig for the posts?
    Thanks

    Reply
    • Blue Circle Products

      Hi Howard,

      We would not suggest using Postcrete for this project as there is no guaranteed compressive strength. It is ideal for fence posts and smaller applications such as small gateposts and rotary lines however not to support sheds or similar structures. In this instance we would suggest our Multi Purpose Concrete or High Strength Concrete. Both are ready to use however not quick setting like Postcrete (normally 2 -3 hours)

      The size of the hole is dependent on the posts but would suggest narrow and deep with approx 25% of the post below ground.

      Reply
  10. Marc

    I have 16 4ft posts and want to bury them 1ft, how much postcrete will i need?

    Reply
  11. terry bryan

    hi – i am assuming i can use this for traditional purposes? I have some left and need to fill in a narrow ‘hole- in an internal floor before covering with carpet. This OK to do?

    Reply
  12. Kevin

    Hi,

    I have a section of Estate Fencing to erect. The posts are 50mm x 12mm flat iron and will be sunk 600mm into the ground with 1200mm above ground. What size diameter hole would I need to suit this type of post?

    Reply
    • Blue Circle Products

      Thank you for your enquiry,

      I would be inclined to dig a 150mm x 150mm purely because anything smaller than this is not practical to dig down to 600mm as the chances are the sides will keep collapsing in. If you have to do several holes to dig I would invest in a split shovel or a narrow trenching spade as this will make digging a narrow deep hole much much easier. If your hole ends up 150mm x 150mm x 600mm you will need one bag per post if you end up with a 200mm x 200mm x 600mm you will require 2 bags per post hole.

      I hope you find this information useful.

      Reply
  13. David

    I’m laying wooden sleepers in my garden what is the best way to do this.

    Reply
  14. Jordan Brocklehurst

    Good morning,

    I have a frame built from 3x 150mm diameter posts (2 uprights, 1 crossbar) – for a hammock – the hole is quite substantial: 450mm x 450mm x 900mm deep…

    I’ve read that you shouldn’t mix postcrete, or let concrete ‘fall’ through water (so that the elements aren’t separated)… if this hole is filled with a 3rd water, the first few bags will fall through the water – would I be better off pouring a little water in, then a bag, then a bit of water, then a bag etc etc so nothing is saturated / separated / mixed?

    thank you

    Reply
  15. Richard Herring

    Using 2m 100x100mm oak posts on galvanised post anchors for a close board fence, how much postcrete will I need?

    Reply
    • Blue Circle Products

      Hi Richard,

      Depending on the design of your chosen ‘post anchors’ Postcrete may not be the best choice of product. If the anchors are to be embedded within the concrete (e.g. a spike with a socket on top to accept the post) Postcrete should be fine. This being the case the hole will need to be 200mm square and 650mm deep as a minimum; this volume would require just over two bags per post.

      If the anchors are a ‘bolt down’ type we would not suggest using Postcrete. Although Postcrete has been used successfully in many such applications, a conventional concrete mixed at a 1:4 ratio (Cement : Ballast) using a fixed volume container such as a bucket to gauge your mix; or alternatively, if you would like a ‘ready to use’ product our ‘High Strength Concrete (40N)’ would be an ideal choice, either of these two options of conventional concretes would be considered the best practice.

      Below are links to our High Strength Concrete (40N) and our ‘Builder’s Guide’

      High Strength Concrete (40N) – https://tarmac-bluecircle.co.uk/product/high-strength-concrete-trade/

      Buidler’s Guide – https://tarmac-bluecircle.co.uk/wp-content/uploads/2018/01/Builders-Guide-170118a.pdf

      Reply
  16. David Woof

    I am using steel ‘I’ beams, size 123 x 76, as posts, to build a low retaining wall with sleepers. The wall will be 600 above ground level and 900 into ground (because of slope). What size hole would you recommend and how Many bags of Postcrete will I need per hole?

    Reply
    • Blue Circle Products

      Thank you for your enquiry,

      Although we are aware of Postcrete being used successfully to support posts retaining soil, Postcrete was designed purely for fencing so we would not consider its use for anything else to be best practice. This would make it a matter for your own engineering judgment. If you do decide to use Postcrete your holes will need to be 250mm x 250mm x 900mm (250mm is a typical spade width) holes with these dimensions will require just under 5 bags of Postcrete per hole to fill them to the top.

      As best practice we would suggest a more conventional concrete such as our High Strength or Multipurpose Concrete, if you choose this option you will require approximately 6 bags per hole. Alternatively you could batch your own concrete and use our Extra Rapid Cement (or if speed of set is not a primary concern any of our bagged cements) at a ratio of 1 : 4 (cement : ballast) by volume; if you choose this option you will require approximately 20kg of cement and 110kg of all in ballast per hole.

      If you require further guidance please contact the Technical Helpdesk (info-cement@tarmac.com) and we will endeavour to help you further.

      Reply
  17. Michael

    I will be putting 8 concrete fence posts, which will also be used for a retaining wall with 4ft fence panels on top. I am putting 3-4ft of post into the ground how much postcrete will I need?

    Reply
    • Blue Circle Products

      Hello Michael,

      Thanks for your question. Assuming your holes are 30cm x 30cm x 100cm (1′ x 1′ x 3’6″) you will require approximately 5 bags per hole, this will leave a few inches at the top of each hole that can be cak filled with soil; if you wish to fill the hole all the way with concrete you will require approximately 6.5 bags per post. You could reduce the Postcrete required by making the holes narrower (25cm x 25cm x 100cm) this would mean you could use 3 bags per hole with a little soil back filled on top or approximately 4.5 bags per hole if you wished to completely fill the hole to the top.

      Reply

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