Problem in setting gate posts in water (high water table)

[Brigadier]

My only comment is based on the ancient oak posts I struggled to remove. Above ground they were falling apart. Below ground and in the water table they were in very good condition even though saturated and swollen. Hence I believe that good quality timber can be set in soil below the water table and they will not rot.

It's what Venice is set on, Bernard, so good call.
It is the lack of oxygen that slows / halts the decomposition process, IIRC.

 

[NicKarla]

I have just removed some wooden fence posts on the opposite side of the garden. They were sitting in water too but the bottom end was not what was rotting. It was at ground level, where oxygen is present. This is reassuring, hopefully if I get some 7" treated posts they will be fine as there will be minimal soil contact and I will slope the concrete away from the post to allow water to drain away. I'm just a bit confused as to why people get so caught up in filling the bottom with ballast to allow water to drain if this is not in fact where rot occurs.

 

[Brigadier]

^^^because without the ballast, you would effectively be sitting your wooden post in a concrete bucket. Which would eventually fill with water (which won't drain away). Which would provide the constant supply of water to rot the post?

 

[NicKarla]

But with no oxygen how will it rot. As had been stated, by Bernard and myself, we have removed posts sitting in water that have not rotted.

 

[noseall]

Being submerged in water does not cause rot. Look at archaeology and historical ship timbers and the reverse happens.

 

[Brigadier]

But the wood will be wet for prolonged periods, just where it emerged from the ground or concrete. Allowing the oxygen-loving bugs to do their worst.
Doesn't matter if the 'root' is secure, if the post snaps at ground level.

 

[noseall]

But the wood will be wet for prolonged periods, just where it emerged from the ground or concrete. Allowing the oxygen-loving bugs to do their worst.
Doesn't matter if the 'root' is secure, if the post snaps at ground level.

Gotcha, yes.

 

[Brigadier]

Thank God for that - I was running out of ways to explain what I meant, without the option of waving my arms about / shouting

 

[NicKarla]

But the wood will be wet for prolonged periods, just where it emerged from the ground or concrete. Allowing the oxygen-loving bugs to do their worst.
Doesn't matter if the 'root' is secure, if the post snaps at ground level.

So are you saying that because the water won't drain at the bottom the top part where the post emerges from the ground will be excessively wet as a result? I'm a bit confused from where you started saying about drainage and ballast at the bottom and then switched to talking about the ground level.

 

[Brigadier]

But the wood will be wet for prolonged periods, just where it emerged from the ground or concrete. Allowing the oxygen-loving bugs to do their worst.
Doesn't matter if the 'root' is secure, if the post snaps at ground level.

So are you saying that because the water won't drain at the bottom the top part where the post emerges from the ground will be excessively wet as a result?

If it rains, the water has nowhere to go (except to evaporate- which it won't, in cold and damp weather), YES.

I'm a bit confused from where you started saying about drainage and ballast at the bottom and then switched to talking about the ground level.

To the best of my knowledge, for wood to rot, it needs to be exposed to:

bugs (fungi?)
water
oxygen

Take away one, and rot is much reduced, or even eliminated.

The rot will occur at the water-air interface. In a concrete base with no effective drainage, this will be at "ground level".


Best practice of putting ballast and drainage at the base of a wooden post is to prevent water pooling around the base; any rain or such will be drained away, and therefore will be somewhat temporary.
However, as you intend to site your post in permanently wet ground, a drainage hole would be pointless / counterproductive.

 

[AronSearle]

there's no place for a spur unfortunately. Noseall has said what I thought about rotting occurring at ground level, I'm just unsure why everyone goes to great lengths saying you mustn't concrete all the way down if it doesn't really rot there anyway.

It is so that you don't put the post into a concrete 'cup' that will hold water.

Decay happens near ground level because you have water and oxygen, having a hole/gap in the concrete allows (in a limited manner) water to drain away.

Though as you say it doesnt matter much in your situation.

 

[NicKarla]

I managed to source some good quality, HC4 redwood 7"x7". It a bit further out but a couple of hours is nothing compared to the additional years I hope to save. All was good until I cut them. I made a separate thread as I thought people might find it interesting to see.