I've put in another fence post, but the hole must have been slightly larger, as the PostFix (1 bag) only came to roughly 4 inches from the top.
Can I top it up with another 1/2 bag?
If so, can I do it straightaway or should I wait till the PostFix I've just filled has really gone off, i.e. tomorrow?
By the way, there's about 60cm of post in the ground.
MM
Yes - sure.
Postfix is not really "structural" - it's more of a bulk hole filling agent that doesn't move - unlike loose gravel or sand.
So putting another few inches on top can be done anytime - it does not need to bond to the existing.
I don't think I'd bother - I'd just ram some rubble in the top of the hole above the concrete.
If you're going to do it at all, it needs to be done at the same time as the first bag so that you get one continuous lump of concrete.
You can eke out the concrete/postfix by judiciously adding a few brickbats as the hole is filled
That's what I would do for the whole hole, better drainage might make the post last 5 minutes longer. Provided you have enough post in the ground well rammed rubble/soil will be good enough.
It's too late for this particular hole. It's already been filled. Now I just need to to know whether I can top up the PostFix from a second bag which I've still to buy (waiting in for a delivery right now).
The general consensus is, yes, I can. I emailed Hanson as well as enquiring here and got a very quick reply:
"The two application approach would probably be okay, though there is increased likelihood that it would form a seam which over time would be more susceptible to freeze thaw / ground water than a single block"
MM
That's an accurate answer. Use it, dont worry. Isnt it cheaper to get separate sand/ballast though?
NT
I've been digging out an old post and no concrete looks like it was just pushed in.
It may be for people used to mixing cement, sand and ballast, but I found PostFix an absolute doddle to use, literally for near-novices such as myself. Also, the price isn't bad. I got a bag from Andrews in Spalding for £4.99, less 10% Diamond Discount for pensioners, and only had to pay a quid more to get that second bag I was referring to from a local builders merchant. I reckon I won't to replace the new posts all the while I am at this property.
MM
That's what the estate builder did on this estate. *All* the posts have been pushed/hammered in. No concrete at all. Perhaps this is why this one post rotted away where the ground is especially damp all year round (it's in shadow from the fence, so only gets to fully dry out in high summer).
(By the way, in earlier posts I said I suspected the post WASN'T rotted where it met the ground, but closer inspection showed that it was rotten all the way through. The post remnant *above* ground however is still as solid as a rock. So a repair spur might have done the job as an interim fix, but quite honestly these 4" posts are as cheap as chips when you're only replacing one or two.)
One other thing I noticed after walking back to the house having topped up the PostFix: All the existing posts are slightly chamfered at the top (cut on a shallow slant) to stop rain water from pooling. I failed to notice this before putting the posts in, so I've got a merry old job sawing a sliver off them! Or maybe get a couple of the fence post caps.
MM
Too late now, but bitumen coating the underground portion of the post makes it last better.
NT
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