# Forum Home Renovation Fences & Screens  Cypress posts in ground - concrete or rammed earth + bitumen paint?

## ChocDog

Looking for recommendation for the best way to install the posts for a planned vertical garden. 
Embedded in concrete (potential rot issue) OR just rammed earth (stirrups etc not an option)?  
The plan is 6 * 120x120 cypress posts with a spacing of approx 2.4m. Between them will be SL62 (or 72) mesh for vines etc. Refer to the awesome pic I marked up while sitting at Airport... 
It will be just in front of the (ugly) back fence its going to hide and same height so wind load should be similar to the fence (low) . 
The garden bed they are going in is about 400mm high of top soil but below that is clay. 
My preference is rammed earth and paint the bottom of the posts with bitumen till above the soil line (looks wise it will be ok as I will mask them to get a clean line). 
Comments? 
Cheers. 
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## SilentButDeadly

Just rammed earth or even gravel. Though I suggest sitting the stump on (even better, attaching it to) a sole plate as well. 
Concrete attracts moisture and the cypress won't respond well to that.

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## Marc

If you are talking about Australian Cypress or Cypress pine, then I would put it in a hole with a layer of blue metal in the bottom and ram more all around it with the back of a fencing bar. Blue metal or gravel or recycled aggregate, does not matter. No need for a bottom plate since in your case the load is only sideways and not vertical.

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## ChocDog

Thanks guys. Sounds like it's time to get the fencing bar out - rammed earth it is. I'll whack a sole plate and some aggregate in there as well. 
Am concerned about rot, reckon bitumen paint extending above the soil line will do much or is it more a placebo effect? 
Cheers
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## Marc

Bitumen paint applied nice and thick is good.

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## ChocDog

Ok, 2 coats of bitumen paint done. Dig holes tomorrow...   
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## phild01

Not sure about that as it also retains water.  Shame creosote isn't around.

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## ChocDog

Why do you say that Phil? I thought the wisdom was that the bitumen would stop water ingress - as long as the paint extended above the soil line. What's your thoughts or experiences? 
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## phild01

Moisture will enter from above the waterpfoofing line and be entrapped.  Once upon a time long ago before H4, I did similar with oregon and it all rotted out within twelve months below the ground line, was perfect above the ground line. For posts I just select resilient timber and let it breathe.  Just my experience with posts I guess. I might leave it for others to comment though.

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## phild01

Depending on soil conditions, maybe I would unseal the bottom of the posts and put some gravel in the bottom of your holes....maybe! 
Bear in mind your original fear _"Embedded in concrete (potential rot issue)"._ Do you not think what you have done is similar! 
Perhaps Marc was encouraging generous use of bitumen like you indicated, around and above the soil line rather than encapsulating it all.

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## Optimus

I'd be throwing the cypress away and getting some redgum

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## Optimus

How long do you need them?

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## phild01

Maybe use concrete footings with flat gal lintels either side... would be nice and strong.

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## Marc

i have seen Cyprus post 40 years old on farm fences, just straight in the ground. those post are smaller and need some help. The idea that water will ingress between the timber and the bitumen is noted but extremely unlikely, more like impossible. 
It is true that Cyprus encompasses a few different species of tree and some are better than others in the ground and also the younger the tree, the worst it does. Hard to predict.

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## phild01

> The idea that water will ingress between the timber and the bitumen is noted but extremely unlikely, more like impossible.

  Not suggesting ingress through the bitumen, rather from above the bitumen line and down.  I think a lot can depend on the actual soil condition and how damp/wet it is!

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## ChocDog

> Not suggesting ingress through the bitumen, rather from above the bitumen line and down.  I think a lot can depend on the actual soil condition and how damp/wet it is!

  Well this has opened up a can of worms of sorts! I hadnt considered ingress through what your suggesting Phil. Sounds possible though. Having a read around the web its hard to get a hard and fast rule based on practical experiences of the best way to deal with timber posts in ground. Might just have to suck it and see what happens! If the thing rots out and falls over in the next couple of years, I'll report back. 
Appreciate all your input and suggestions guys - food for thought. Cheers.

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## ChocDog

> I'd be throwing the cypress away and getting some redgum

  Bloody restumpers - could've have guessed you'd say that! ;-)   
How long do I need them? 3m approx. 2.2 above, 0.8 below. Or if you mean years (?!), 10+.

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## ChocDog

> Bear in mind your original fear _"Embedded in concrete (potential rot issue)"._ Do you not think what you have done is similar!

  No, not really (but I see where your coming from). The big problem with posts in concrete is that with time the timber shrinks and hence opens up a gap b/w the concrete allow water to enter and sit there. The concrete acting like a cup containing water (somewhat reduced if no fines concrete mix used I believe). Bitumen paint onto the timber, shouldnt promote this condition but I hadnt considered the wicking scenario you are.

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## phild01

> The big problem with posts in concrete is that with time the timber shrinks and hence opens up a gap b/w the concrete allow water to enter and sit there.

  Not so sure about that. Posts I have removed have not had that gap, as well the timber will not be drying out, in fact it will expand due to moisture.

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## Optimus

> Bloody restumpers - could've have guessed you'd say that! ;-)   
> How long do I need them? 3m approx. 2.2 above, 0.8 below. Or if you mean years (?!), 10+.

  Haha, hmmm 3.o are hard to come by. I have a high job coming up in a month or so. I'll touch base and see how you've gotten on.

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## Marc

Phil, yes, I understood your idea and it seems plausible on a hard surface like fibro cement or concrete where the bitumen can get dislodged. I don't think that the film of bitumen would peel off the timber and allow ingress of water all the way down. If the post is in a riverbank and the tidal water goes above the bitumen, the timber would swell and some of the water would en up on the inside, however timber is not a sponge, and cypress is dense and oily enough to repel water if submerged, let alone above ground with occasional rain water. The idea that rainwater will find it's way on the inside of the bitumen film is not feasible in my opinion.

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## phild01

The water only has to stagnate at ground level to rot, so moisture doesn't have to go down too far.  It's not a matter of the bitumen breaking free but just capillary action drawing moisture down from above ground level to where it can't evaporate.  Only time will tell for this one. 
These days, if I was to put a post in the ground, it would be treated.

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## ChocDog

> The water only has to stagnate at ground level to rot, so moisture doesn't have to go down too far.  It's not a matter of the bitumen breaking free but just capillary action drawing moisture down from above ground level to where it can't evaporate.

  Isn't oxygen required for rot to have a significant affect though? This is why, to my understanding, the critical rot zone of posts is the soil interface - where there is a mixture of damp soil and free supply of oxygen. Hence house stumps are generally in good condition well below the soil surface where there is no oxygen (especially if the ground is well tamped). But a caveat, I am definitely no expert here - hence why trying to find what the best practice is due to wisdom learnt over the years!

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## phild01

I'd be interested testing the theories but it would take some years. I will add that I have seen many hardwood posts that break at ground level that still have some strong timber left in the ground, and I believe there is little you can do about it without a rot resistant treatment. Sure the waterproofing can stop ground water but it won't let the timber breathe absorbed water out.  I think I am out of this one for now.

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## phild01

Here's a video that might help you a bit.  Note the use of diesel/oil mix and then asphalt paint and what I suggested earlier to leave the cut end of the post free to allow drainage. https://www.youtube.com/watch?v=yd0nDUYHi3U

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## ChocDog

Ok, got this finished a few weeks back. And just for Phil, I lopped off the bottom of the posts. Hope he knows what he's talking about ;-) They're also sitting in/on a bed of crushed rock.

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## phild01

> Hope he knows what he's talking about ;-)

  Usually, the rest I make up :Biggrin:

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## Nznative

Hi. Just came across this thread. Would love to see an update of how it’s looking...!   
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