Setting posts for fencing [Archive]

Tiger

16th May 2005, 02:47 PM

Could someone out there tell me how to set fence posts with the soil/cement method where the mixture is tamped repeatedly. I would like to know what the proportion of soil to cement should be and how hard to tamp. I have had a go at this before with a heavy crowbar but it was a lot of work and the post moved anyway later. Does the soil have to be dry orpartially wet? Saw a guy put in a few posts in about an hour, he didn't seem to be exerting himself much and only did what looked like minimal tamping.

Any responses (constructive) are appreciated.

MrFixIt

16th May 2005, 03:45 PM

[snip]where the mixture is tamped repeatedly.

Tamping is where you are pounding on the top of the material, I don't know if there is a particular name for what you mean - other than "mixing" :D

I would like to know what the proportion of soil to cement should be"soil" ?? DO you mean sand? 4 sand and one of cement is a good mix. You should also have some "bluemetal" in the mix (maybe 1 to 2 shovels full).
and how hard to tamp.You only do this "mixing" to ensure that the sand/cement mix is properly settled, ie no air pockets or gaps. You do not need to pound it around the base of the post to gain "extra strength".
I have had a go at this before with a heavy crowbar but it was a lot of work :D Try something lighter like a stick or the blade of your shovel. You are not trying to impact on the mix, only remove space or gaps in the mix.
and the post moved anyway later. Most likely because the surrounding material ie the ground around the post was not firm enough to hold the post, or perhaps the post was not deep enough in the ground? I replaced a Jarrah (closed) picket fence not too long ago and used jarrah posts these posts were at least 2 feet in the ground.
Does the soil have to be dry orpartially wet?It doesn't really matter, as long as the soil is FIRM. Wetting it can cause the hole to collapse and/or make the surrounding area soft. If the soil is damp it helps the concrete mix "cure".
Saw a guy put in a few posts in about an hour, he didn't seem to be exerting himself much and only did what looked like minimal tamping.Sounds about right to me :D

For rigidity, you need to keep the post hole as deep and as narrow as possible. 12"/300mm square is a good size. Prepare the sand/cement/bluemetal mix BEFORE putting it in the hole. DON'T do it like they do on tv and pour the dry mix and water in the hole. :( :(

BTW a six inch hole surrounding a three inch post with the mix put in like on tv (dry mix / water in the hole) is almost no better than the post in the hole by itself.

julianx

16th May 2005, 05:14 PM

Hi
I've used the tamping method before and to be honest I find it easier to simply concrete the posts in. If you want to ram them in here's what I did
make sure holes are 600 mm deep min
use poured concrete for all corner posts and gate posts
I never used cement with the mix, though I suppose 1 to 10 would stablize the soil.
don't use this method if the ground is too sandy
make the soil damp not wet
ram about 200 mm at a time with length of fence post or rail, it has to be flat not pointy like a crow bar
This is the way I've done it before but don't take it as gospel, and like I said I find concreting them in easier

rackrussel

16th May 2005, 06:48 PM

goat

16th May 2005, 06:54 PM

Hi Tiger, unless you have very sandy soil i wouldn't worry about mixing cement with your soil i was a contract fencer in western central queensland for a while and all we did was tamp the soil back in to the hole the secret is don't be tempted to tamp too much soil at a time ,a little soil tamped more often will give you a better result. I have my own property now and i still use that method works great.

johnc

16th May 2005, 08:55 PM

With tamping you need to put only a little bit in at a time and tamp home. The back of a crowbar works best, but like the earlier posts soil type can vary the result. All the fence posts put in here are tamped soil only and solid as a rock, if you throw all the soil back in and just ram from the top you will only firm the top and leave the rest loose hence wobbly posts. Concrete usually hold moisture around the posts causing them to rot a bit faster, but its easier to just chuck the quick mix in dry and after a quick ram to firm the top flood the post with water or if really keen you can wet the premix first and after getting the post level wait for it to dry.

JohnC

microcorys

16th May 2005, 09:38 PM

All of the replies you have had so far have their merits. Believe me I have set too many fence posts to mention so here is my method:- depends on your soil type of course so I am presuming clay loam or similar: make the post hole 600mm deep and about twice the diameter of your post,ensuring the sides are nice and vertical. try not to disturb the surrounding soil too much.Set the post in position and brace temporaraly on two sides at 90 degrees to ensure vertical. Rapid set concrete is great but quite expensive, but 20kg bags of concrete mix do the trick (1 bag per post). It's best mixed in a barrow and tamped to remove air with a stick or similar. Tamping with a crowbar will push your post out of alignment. Try to use the minimum amount of water in the mix to ensure maximum strength.
Have fun

journeyman Mick

16th May 2005, 11:51 PM

boban

16th May 2005, 11:59 PM

Concreted in posts = rot
Tamped in posts = lasts a lifetime

Mick
Please excuse my ignorance, but why do the concreted ones rot?

Would the problem be solved if the concrete is allowed to finish above ground level and tapered?

Interested to know because I am going to build a cubby house with 6 poles (H4 treated crap stuff) about 1800 off the dirt. I was going to concrete them in so I like to know how to avoid the rot you speak of.

journeyman Mick

17th May 2005, 12:20 AM

Boban,
even if you mound the concrete up above ground level you'll get rot. the timber will expand and contract with moisture changes and there will be a small opening in the conrcete around the post. Water will get in here and not dry out very quickly. Add to this the fact that your timber will probably be a bit green to start with and shrink over time which will give you a bigger gap for water to get into. Materials wise it's cheaper to just ram earth around the post, but it's more expensive when you factor in the labour. Yhis is why most contract fencers (of domestic not rural type fencing) use concrete. Cheaper and quicker.

Mick

soundman

17th May 2005, 12:22 AM

I agree with micks method on heavy soils with wooden post, bang em in right & they'll stay firm.
The big advantage is that you end up with a compacted gradient arround the hole which is more secure than concrete.

I've found with skinny metal posts ramming dry premixed cement mix does the trick. Moisture in the ground will set the cement off in a couple of days but the post is firm anyway. If the ground is dry sling a bit of water in the bottom of the hole. A wet mixed collar just at the top helps with corrosion.

There are as many ways to set a post as as ther are days of the month, But I know micks methosd works.

You do need a bar with a big round disk on one end.
Don't kid youself, it is hard work.

cheers

johnc

17th May 2005, 12:33 AM

It is as Mick said they hold water, it gets into the gap between the post and concrete and cannot get away. If you really must use concrete sit the post on the ground in the hole and place about 75mm concrete in the hole, tamp with soil up to near the top and make a similar concrete collar up there coned so the water will run away from the post, the condensation still gets between the post and the concrete but is wicked away by the soil. Like Mick I've done a fair bit of rural fencing before the days of the post hole rammers and if you are carefull you do not get your square town posts out of level, simply check levels as you go and tamp a bit harder on the side you need to push away from, those post levels make life easy these days . To give you some idea four blokes with a tractor auger and crowbars could do about 1km of posts per day, you simply run one post out about four from your last and then sight between the posts to fill in the gaps, the fourth bloke coming up behind with the wood borer for the wires does the sighting. Hard work and something I never missed I might add.

JohnC

journeyman Mick

17th May 2005, 12:48 AM

...........Hard work and something I never missed I might add........

Yep, same here, avoid anything like it like the plague. ;)

Mick

Ashore

17th May 2005, 01:09 AM

You didn't say what you are using for posts but if possible on the section of the post that will be underground affix two battens at right angles to the post and each other using treated pine etc... you can do this by flattening two arears at the bottom of the pole And nailing the battons on , I usually use galvo nails.
Once in the ground it dosn't matter if you concerte or tamp the braces give the post better strength in all directions but as previously get them straight and brace them dont try ot align straighten them later espically if you concrete

Don't take life too seriously; No one gets out alive.

microcorys

17th May 2005, 02:30 PM

Concreted in posts = rot
Tamped in posts = lasts a lifetime
My brother and I farmed for a few years and we put in a few posts (low thousands) plus I've put in more than a few posts for pole homes, sheds, decks verandahs etc. Concreted inposts will generally rot off just where they exit the concrete. Dig a hole about 600 dia for fence posts, throw a bit of coarse gravel in the bottom to sit the post on, this will drain any water away from the bottom of the post. Stand the post in the hole and steady it (iether a helper or a few bits of timber. Throw a few shovel fulls of dirt in and tamp with the pointy end of the bar, continue till you've got about 1/3rd of the hole done, then swap to the spud end of the bar. keep throwing in a few shovel fulls and tamping, you should run out of soil before the hole is full. Get dirt from elsewhere and keep filling and tamping until you get above soil level and you build a cone shaped collar to shed the water. Fences and sheds that I put up 23 years ago like this are still fine, and we live in a very high rainfall, humidity and sunlight area (read: great conditions for decay)

Mick
Interestingly and contrary to popular opinion, placing coarse aggregate at the bottom of fence posts will create a perched water table above the aggregate, thereby increasing the chances of wet rot.(refer to p. 92, Drainage For Sports Turf and Horticulture, Keith McIntyre and Brent Jakobsen). The proven theory is that water will not move through a soil profile from a fine textured soil (surrounding the post and above the aggregate) into a courser textured medium (the aggregate) until the profile is saturated. It is therefore preferable to have the base of the post in direct contact with the soil. Treating the below ground part of the post with creosote or sump oil can greatly increase the longevity of the timber.
Cheers, Micro

Stylesy

17th May 2005, 04:01 PM

Micro,

I knew something was nagging me, and that was it - though I still hate McIntyre's books on turf etc from my Burnley days studying horticulture. :rolleyes: Comes down to cohesion between particles (water particles in this case) if I can still remember - the strong cohesion in the soil (especially clays, etc) holds the water particles within it, while the larger spaces between gravel (and sandy soils as well) do not have the same cohesive force to draw water into them. :confused:

I keep thinking there was something I learned at uni, I just can't figure out what it was. ;)

Cheers, Craig.

microcorys

17th May 2005, 05:04 PM

You got it stylesy, It paid off to pay attention in class after all :). The same concept applies to the base of retaining walls, drainage lines etc. I agree the text is boring but makes enormous sense. Handreck and Black is more readable.
Cheers, Micro

microcorys

17th May 2005, 05:31 PM

Just had another thought on the adhesion/cohesion/capillarity concept. How about using crushed basalt fines under and around the post, right to the soil surface. If well tamped the capillary attraction of the tiny pore spaces in the surrounding soil should keep the timber post relatively free from water. Any thoughts Craig? and if it works we should take out a patent:)

Cheers, micro

Ashore

17th May 2005, 05:55 PM

Ever thought of a nice brick wall..... or a hedge.....or better get your neighbour to put the fence up

Stylesy

17th May 2005, 06:14 PM

How about using crushed basalt fines under and around the post, right to the soil surface.

Micro,

While this should work to draw water away (and I remembered the reasoning - all to do with increased surface area within fine particle soil profiles), the increased particle size such as basalt fines would not provide the support needed. I guess it would act a bit like sand - you can compact it, but only to a point - the spaces between will always be dictated by the size and shape of the particles. This means you may end up compromising too much stability, as even when compacted the fines may move over time, more than standard soil (even finer particles) would. :confused:

And I'm thinking too much today, but it still beats working :D

Cheers, Craig.

microcorys

17th May 2005, 07:11 PM

OK Craig, I think you are probably right about the stability. The fence posts might be rot free but a bit wonky in time. Ah well, forget about rags to riches then.
Cheers Micro

seriph1

18th May 2005, 08:24 AM

it's interesting what Mick said about rot (god knows I speak enuff of it). Having watched several hundred American home renovation type shows, I have seen maybe 30 fences put in and none of them had concreted-in posts. I guess we think we need it to stop the fence from falling down, but tamping is pretty bloody tough! My next (front, picket style) fence will not be concreted in..... in fact, I have toyed wit hthe idea of making it in sections but doubt I will.....seems an unnecessary strain on the body to lug the things down the front after making them.

:D

MrFixIt

18th May 2005, 11:22 AM

to make it easier on yourself i would use rapid set concrete. about half a bag per hole just pour it into the hole add water
use shovel/stick/whatever is handy to help put a few 'holes' in the mix and you are done

Make it even easier on yourself :D and don't waste your time with "half a bag". Unless it's a VERY BIG bag, such a small amount of rapid set concrete does nothing for support, it only adds a little extra mass at the base of the post.

Using this method of adding the water to the dry mix ALREADY in the hole prevents a PROPER mix being done (unless you add too much water to enable easy mixing).

I was stunned when I saw this method first used on the various "backyard" programs. A "piddly" little hole surrounding a post with a "skin" of rapid set concrete around it! What a waste of time and effort and money. THAT amount of concrete is just a waste as it does very little for support!

neddy

25th May 2005, 02:36 PM

Journeyman Mick says that posts will rot when concreted in the ground because of the small gap which occurs and water gets in....my question is - can you fill this gap when it occurs with "no more gaps" to keep the water out? "No more gaps" should expand and contract with the gap. What do you think?

seriph1

25th May 2005, 03:53 PM

I believe it is the concrete that stops or retards the water getting OUT from around the wood that is the culprit...... and I believe also that water will get in no matter what is done

neddy

27th May 2005, 08:38 PM

Hi Journeyman................one question......is the tamping method still good for the posts that have to support the gate, especially the longer driveway gate? Or should these be concreted in? Is there a more long lasting timber post than cryprus? Thanks

journeyman Mick

27th May 2005, 11:07 PM

Neddy,
tamping is still fine for a gate post, but depending on the size, weight and length of the gate(s) you may need to use an oversize post, go really deep, brace it back to another post or corner or all of the above. And sorry, no I don't know any formulas for determining the sizes or bracing required, it varies with the soil type, we just did it by experience/local practice.

Mick

johnc

28th May 2005, 12:21 AM

Ned,

An early way of bracing around here was to put a cross at the base of the post out of 2" x 1" or thicker and brace it at 45 degrees back to the post. Any I pulled out seemed to only come out about 6" from the post and none seemed to shift under the weight of the gate. I could never get excited about the method, and simply braced back to near the next post in line. Generally timber that does not break the surface is very slow to rot, you need both water and air to create rot and in tightly compacted soil there should be little air and if a well drained soil not a lot of water. As for no more gaps to stop water, even if it did work it would not prevent moisture building up in the gap as water will draw through concrete and expire through timber to penetrate the cavity between post and concrete.

JohnC

neddy

1st June 2005, 08:18 PM

Thanks Jonnyc......has anyone ever heard of using scoria to support the post....ie. sit the post in the hole and simply tip in the scoria, as you wiggle the post around the scoria compacts untill the post is as solid as............a farmer told me this but I'm a little bit wary of the method.

Ashore

1st June 2005, 08:56 PM

has anyone ever heard of using scoria to support the postme Scoria, if you get it as its forming it sets as hard a rock
mind you the post might not last.

Don't take life too seriously; No one gets out alive.

Barry_White

1st June 2005, 09:22 PM

This might be a bit late posting but I have put up few rural fences and was taught by my father-in-law who spent 70 years putting rural fencing up.

No rural fence is put up using concrete, just dirt. Some of these rural fences have been standing for up to 60 years.

Corner posts or gate posts or strainer usually have a stay to take the strain of the wire but the posts depending on the length of the fence run the gate post or corner post can be up to 600mm in dia. remembering a fence run can be up to 2 klms or more with a 14 foot gate hanging off the post.

The hole for the post usually has about 3 to 4 inches clearance around it. The dirt is put into the hole in layers and the most important part of ramming the earth is the bottom six inches and the top six inches. Posts should be 2 feet into the ground.

The problem with round posts is over the years the sap wood rots away quicker than main timber. That is why split posts or sawn posts last much longer.

Remember none of these fences use treated timber, just good old Australian hard wood like Stringy Bark, Red Gum, Yellow Box or Iron Bark.

Tiger

2nd June 2005, 07:45 PM

Never too late Barry. Thanks for all the information boys (and maybe girls?). I am now prepared for the next fencing job which I might undertake. I've just realised how much collective information this forum has, awesome.

seriph1

2nd June 2005, 07:50 PM

me too! I will be re-doing front and side fences and as far as I can tell, provided I adhere to some obvious principles, no cement will be necessary

Thanks everyone

neddy

2nd June 2005, 08:18 PM

Thanks every one. I love your work Big Bazza. I'm now convinced and I'll be using the rammed or tamped earth method with cryprus pine posts at 600mm deep. I'll go 700mm deep for corner and gate posts. No concrete for me. Thanks again every one.

ps - Barry, have you heard of using scoria to fill around the posts or using dry cement mix in with the dirt?

Barry_White

2nd June 2005, 10:34 PM

ps - Barry, have you heard of using scoria to fill around the posts or using dry cement mix in with the dirt?
Hi Neddy

I haven't used scoria, but I guess it would cost an arm and a leg to get here, and anyway the soil in my area is granite. Granite is a soil that compacts down like concrete after it has been wet a few times. Up here it is used as road base by the RTA and some of the local councils.

It is ideal for compacting. Looking at the properties scoria I don't know that it would compact so good. May be ok to be used as an aggregate for concrete.

yogifnbear

12th March 2024, 09:25 PM

this moreso regarding paling fencepostrs than rural..
i usually do the ramming method, mix cement with dirt, slightly damp, and pack down every shovelfull with the back of the crowbar..

but there's another way that i wouldn't mind a bit of feedback on, 600mm deep hold, bottom of post cut to a V, por a bucket of water in, pour a third of a bag of cement powder in, put a shovel of dirt in, about equal to the cement , then slosh it all around to a thick cement laden mud, plonk post in, leave it to set a few hours, maybe back fill with a bit of tamping to the top..

its basically labour saving when you are doing a dozen posts, what i'm still wondering is long term, i am hoping they dont rot off as bad as when concrete is used, as its more a solid mud , and the tamoped soil on the top half of the hole should stop the water settling like a collar, as when you use wet concrete, or am i just kidding meself..

over a short period , 3 years, the posts put in this way are still solid as (the mud sets solid underneath), just hoping that over 5-10 years its not going to all end in tears if they do end up rotting above the cement mud level....