Fence post mounting

[Andrew Gabriel]

The recent winds have seen the end of a boarded arris rail fence. The posts are 100mm x 100mm, 3m apart and the fence about 1.6m high with

3 arris rails per section. It was probably 30 years old. The posts rotted off at ground level about 15 years ago, and I hammered post sockets into the ground and lifted the posts with the panels attached into the sockets (which was one hell of a job - they were damn heavy). I think it did well to last another 15 years, but now both the posts and arris rails have rotted, and I think that's it.

I intend on mounting the replacement posts so they stop above the ground. One possibility is to reuse the post sockets, but the one I've uncovered so far under the undergrowth and collapsed fence is no longer vertical, so they may have had it too.

Another thought is to use concrete repair spurs set in concrete, with the posts bolted to these. There are some repaired posts in the garden like this already - they've been there 20+ years and and rock solid.

Any thoughts on concreting these in? I can't believe one bag of postcrete is enough for a 1.6m high fence on 3m spaced posts. Is postcrete a compromise over using a real cement mix? If so, what's a good volume per post, and what concrete mix?

Also, is there a different name for arris rails which instead of being flush with the post faces are mounted on the surface so the boarding is spaced slightly away from the post faces? Instead of triangle section, they are almost rectangular but the top surface is cut with a slight slope to prevent water pooling. (This is what I would like to use and have seen elsewhere, but not what the fence used before.)

TIA Andrew Gabriel

[Mathew Newton]

Andrew Gabriel, is that really you?

Over the countless years I've been on this group I don't think I recall ever seeing a question from you - you've always been the one helping others! :-)

(And, apologies, no advice from me to offer other than I've heard nothing but good things about Postcrete and that it generally is considered perfect for its job and not worth trying to improve upon, even when it is an issue of quantity)

[harry]

The problem is even worse now, wood preservatives are such crap these days. The fencing spikes are the best solution to rot I find. Plus give the ends of the posts a good soak in creocote/similar. In exposed situations, braces at 90deg. to the fence run are the best solution if you can fit them in. OR

[jkn]

+1 - I *always* read what Andrew Gabriel has to say on uk.d-i-y, even when I have no interest in the actual subject ;-)

Sorry Andrew, I too have nothing substantive to pass on to you. I hope you get some better replies that ours. But at least some of us heartily appreciate your presence here...

J^n

[Chris J Dixon]

I built a pergola last year, and used

I decided that the metal to be embedded was a little short, so dug the hole big enough to stand them on a couple of old bricks, embedding the whole lot in 1.5 bags of postcrete.

Being a structure, I suppose I am more concerned with the whole lot lifting/ pulling out, rather than blowing over.

I also have some timber posts for a trellis that I postcreted in about 6 years ago, and are still in good condition.

There seems to be a product data sheet and calculation tool here:

Chris

[Andrew Gabriel]

Wow guys, thanks!

[alan_m]

I had reasonable success with delaying the rot in wooden posts by taking the concrete used secure in the ground to above the soil level. IMO the mistake most people make is to put in the postcrete/concrete and then fill the rest of the hole with soil. The post always rots at a soil/air boundary.

[Chris Green]

In general I don't use concrete at all if possible, it tends to keep water/dampness around the post where it enters the ground. I have a lot (probably one to two hundred) wooden posts around our smallholding and the longest lasting ones are simply banged into the soil. The quality of the posts is important, I have some original ones (which were good ones!) which are now well over 20 years old and are still sound whereas other not so good (and not so old) ones have failed.

It's quite difficult to be sure which suppliers' posts are best, ones where the supplier talks about UC4 (or HC4) treatment are probably good. Good 4"/100mm by 6' long posts now cost around £5 or more, back

20 years ago I could shop around and find them at about £1 each!

... and modern preservatives are not so bad, apparently failures reported to a wood research centre that studies this sort of thing are no more now than before the CCA (copper/arsenic) treatment was banned. Just make sure that the posts you get *are* UC4/HC4 treated, they will often be date stamped and even have a 15 year guarantee.

[Dave Liquorice]

It's how far into the ground the post goes that stops it falling over rather than a mass around it. Postcrete is just a quick and simple way of filling the space around the post. Rammed earth will do just as well. Best if the post is snug in the hole, so a post borer or post hole digger thingy rather than an 8" spade. Rule of thumb is 1/3 total post in the ground so 6' out of the ground, 2' in - 8' post.

[Robin]

Is it just me or...

[paul.mccann]

Installing a rabbit proof fence about 30 years ago we used pressure treated timber for the posts but ran short for the last 3 posts where we used atandard round posts. Having given up on the vegetable gardening 20 years later I decided to remove the fence posts. Every pressure treated post came out as new and in fact I reused them but the atandard posts had all rotted at ground level. We get these posts from a manufacturer of telegraph poles so they are the genuine pukka article. I dont believe in setting timber posts in holes back filled with cement The timber wille inevitable shrink away freom the concrete and allow water in.

[newshound]

No.

[Robin]

though it (a) is a reflection of the common advice to sink 1/4 to 1/3 of the post - depending on soil, wind load etc. and (b) possibly to be welcomed as part of a cunning programme of neurological stimulation for declining Usenet users

[Chris Hogg]

+1, and with flaunching around the top of the postcrete to direct rainwater away from the post.

[Peter Parry]

This is what I used to repair a 7ft high fence which catches the wind as it comes around the building. The original wooden posts set in concrete had rotted and broken (albeit after 20 years)

I used Postcrete on the advice of a builder. One bag did one post. It has lasted for a few years so far and enabled me to continue to use the old fenceposts (sound above the rotten base) which I attached to the concrete posts using stainless steel rod rather than coach bolts.

[Vir Campestris]

I've got some raised decking sitting on those. They are rusting away. I'm not sure they'll last much longer than wood would have.

Andy

[alan_m]

Worse than that - on some powder coated items it appears that the coating doesn't adhere well to the item and just forms a waterproof outer layer. When the coating begins to crack water gets in, capillary action draws it much further in from the surface defect and remains trapped between the metal and the power coating.

Its often worse on objects that are designed to be hit such as these fence spikes. The coating can be some what brittle and the act of banging them in causes hairline cracks in the powder coating.

[Vir Campestris]

That sounds scarily familiar. I didn't know there were any good ones.

Andy

[polygonum_on_google]

In our last house, which only had a short fence, one post lasted without obvious damage while the rest all suffered right up to total failure. The one that lasted, I had made quite a large hole. Put fairly coarse gravel the bottom and made it dead flat and tamped down. Stood the post on the gravel and then filled the sides with concrete (might have been postcrete - far too long ago to remember). That meant any water could, eventually, drain away.

In our current house, the builder has done what looks like a fine job with every post wrapped in something that looks a bit like roofing felt to about four inches above ground. Only about three years old so not really tested.

[Jim K..]

There are good & not so good versions though... I like the heavy hot dip galvanised ones, the brown "powder coated honest" ones are sh1te imho (as is everything that is "powder coated", it just flakes off back to bare metal in no time)...