Fence post reinforcement?

Discussion in 'Landscaping and Outdoors' started by SteveMJ, Jan 7, 2014.

  1. SteveMJ

    SteveMJ Active Member

    As some of you have been so helpful with my broken posts and panels problems, I will ask more on the existing fence posts that are almost certainly weakened.

    Some (maybe all, if I tested them) of the old posts do not not feel as solid as the new ones I have replaced and recently fitted (see my question here http://community.screwfix.com/threads/fencing-repair-spur-size.140399/)

    I've gone off the concrete repair spur idea, because of the exisiting concrete lump at the base of the old posts.

    I would like to re-inforce the older fence posts and was thinking about the approach outlined in the diagram below:

    • Use the 'old' broken fence posts cut down to form spacers to allow clearance of the concrete.
    • Fit a reinforcing 75 mm fence post using a fence post spike (75 mm proposed, as I can see that driving a spike in 600 mm deep is easier than one for 100 mm being driven 750 mm).
      • The 75 mm spikes advertise that they are for 1.8 m posts, plus the existing posts are not broken.
    • Not sure how to fix all the posts and spacers together?
      • The longest coach screws I can find are 200 mm long, which leaves only 25 mm into the original fence post. This does not seem enough to me.
      • Threaded bar and nuts/washers at each end.
    So how does this approach sound? And there are some queries in the details above too. Lastly, would a 7 lb sledge hammer be adequate to drive the spike in? And could I used a piece of scrap timber to drive the spike instead of the 'drive-in tool'?

    Any tips in keeping the spike vertical and ensuring it doesn't drift due to stones of whatever is unknown underground?

    Thanks for the advice, Steve

    [​IMG]
     
  2. joinerjohn1

    joinerjohn1 Screwfix Select

    Why not replace the whole fence(including posts? No need to dig out the old ones (apart from the first and last old posts. Dig the first post out (where your starting and concrete the new post back in. Cut a fence panel in half (height ways) Fix this to the first post, and dig out for the second post and concrete in. (fixing the half fence panel to it) Next use full fence panels, all the way to the end, fixing posts and concreting in as you go. the new posts are dug , in between the existing posts (you cut these off as you go along) Much better (and easier) than having to dig out the old concrete. ;);)

    Personally, if your going to do it the way you suggest, I reckon you'll need a bit more than a 100mm spacer for the spike, to clear the existing concrete. ;);)
     
  3. SteveMJ

    SteveMJ Active Member

    Thanks John,

    A couple of reasons why to reinforce. I've three panels down (one swinging) that have had the posts replaced, so that work has been done. And in total there are 14 panels, so a corresponding number of posts that are holding up OK for now.

    I also have a couple of gate gate posts I would like to reinforce too. The gate needs almost hammering to shut in the winter and the lock bolts aren't long enough in a dry summer :-(

    Total replacement is a lot of cost and effort, where IMO the reinforcement would represent a small fraction of that cost and effort and extend the fence's usable life considerably.

    From what I've seen , so far, the concrete does not extend more than ~100mm from the posts. Of course sods law say that it will (especially now I've claimed otherwise).
    --
    You were directing me away for the reinforcement; do you not think it worthwhile?

    Cheers, Steve
     
  4. Sean_ork

    Sean_ork Screwfix Select

    this simple task is being made more complicated - nice drawing but not a great method

    just as an aside, seeing as you've had panels blown down, have you pondered replacing a good few with a more open design which allows the wind through - plant a few climbers and it'll be covered in a few years, and will look rather pretty
     
  5. wiggy

    wiggy Screwfix Select

    This is your best bet, ignore the spec in the picture, but something like this.
    This was the only picture I could find, but you get the idea.
    What your suggesting above is nothing more than a diy hash job.
    Or dig around the existing concrete and add some more. Fence posts get their strength from the depth they are in the ground.
     

    Attached Files:

  6. SteveMJ

    SteveMJ Active Member

    I'm pleased you didn't use the 'bodge' word :)

    If the spike and 75 x 75 mm post is claimed to be good for fences up to 2 m then why wouldn't that be improved if attached to an exisiting post?

    If the depth in the ground is important, why would adding more concrete help. Assuming that I add concrete near the ground level. If I could add the concrete at the post's bottom 400 mm below ground, then I would have removed the existing post anyway.

    Isn't my approach variation on using the concrete repair spurs that are widely sold?

    The diagram you posted looks to require building a long trough and adding a large amount of soil along one side of the fence. It also seems to substantially rely on a 75 x 50 peg. Am I mssing something?

    I am not seeing (yet?) the advantage of your approach over what I've proposed.

    Struggling still to see the best way, Steve
     
  7. wiggy

    wiggy Screwfix Select

    post spikes = rubbish
    75mm posts = rubbish

    I would never use either

    as jj says you will hit the concrete.

    read the replies you have received over the 3 posts you have put up.

    JJ says it in his above post, replace the lot.

    and the out rigger detail will be a lot stronger and cheaper than your spike proposal

    Its a hole in the ground with a post in it.
     
  8. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Just my 2pennethworth:

    Trying to support a 4" post with a shorter 3" is like having someone hold a ladder vertically and letting someone climb up it. The weight above it will lever it over.
    Try purchase one of these, attach a couple of feet of 3" post into it when bashed into open ground, and see how much it moves as you wobble it.
    Then ask yourself instead if one hefty lump of concrete with a post in it, would a third generation fixing(loose concrete old post, spacers, spike in ground) be as good ?

    I would suggest getting the old post out. Reason being, if the ground is waterlogged, dig around the post and the post shouldn't be too much trouble to move about and take the whole thing(concrete an' all) out in one go.
    Your only problem there is that when you've got it all out, you'll probably have a foot of water in the hole. In that case, I'd drive a 2" hole down 2' with a pile-driver(or scaffold pole) to drain the water, chuck some dry cement down the post hole, then sort out fixing the new post.

    ........or tie it all up and wait until the world dries out a bit!!!!!


    Mr. HandyAndy - Really
     
  9. Hi Steve.

    As a prize bodger masel' - who has tried every short-cut with fencing - I have to agree whole-heartedly with the above.

    Spikes are indeed rubbish. The spikes themselves might be firm enough in the soil - tho' that depends on the quality of soil - but the posts only slip into them around - what? - 5, 6 inches? Wobblesvile.

    It'll help, of course, but it'll be a fair amount of work for a mediocre gain.

    If you don't want to redo the existing posts into fresh concrete, then the single best - strongest - method of reinforcing is what Wiggy says; a triangulated brace. You don't need a trough of any sort, just a short post (and your metal spikes with a foot of 3" post in it would be ideal) hammered into the ground 2 to 3 feet away (in front or behind) the existing post. And then a short length of 3x2 or similar screwed/bolted through and going from near ground level (in the spike) to as high up the 8' post as you can get away with appearance-wise. This will immediately have a dramatic effect.

    Another thing you can consider is to examine why some posts feel less secure. Can you see movement in the ground - is there a small gap forming between the concrete boot and the surrounding soil? If so, mix a small batch of concrete or mortar (any mix 3:1, 4:1) but don't add water. Get a prodding stick of narrow enough diameter to slip down the visible gap (you may need to trim away any grass or scrape away a couple of inches of soil to expose the gaps) and trickle the concrete mix down there tamping it down as tightly as you can all around the existing concrete boot.

    Oh, and if you want a spike to go into the ground vertically, you are best off using a thin steel bar or similar to make a small diameter hole in the ground first. It doesn't have to go all the way down, but it should give the spike a good straight start. (And, yes, they do deflect sideways if they hit a stone...)

    Yes, a lump of timber is ok instead of the proper drive-in tool, but you'll find it'll splinter and you'll wonder why you saved a few quid doing it this way.
     
    Last edited by a moderator: Jan 8, 2014

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