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Post in ground techniques

 
steward
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Josiah made a video about what we do these days

 
pollinator
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I know this is about post in ground, but I was in China a couple of weeks ago and looked at wood construction which used no nails.

The wood pillars just sit on stones that hold them off the ground.  Friction holds them in place and of course they have very heavy tiled roofs to increase the friction.  The wooden bracket system transfers the load from the roof to the pillars.
The wood was also painted with something to prevent insects eating the wood.



This is the Piyun tower on the Ancient City Wall of Zhaoqing built about 900 years ago.  It was renovated in 1989 but I don't know to what extent.
I'm guessing the pillars held by friction wouldn't withstand the lateral forces of an earth bermed structure but can anyone make an intelligent guess?  Maybe it would just need some cross bracing at the right points?

Anyway, the point is, do we really need the posts in the ground and can we not just place them on top of the ground?
 
Graham Chiu
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I was thinking about precedents again.  A wofati is like a cave opening so what do miners do?

It seems that they also don't bury the timber props that support the walls and roof.  They can dig a 25 mm area for the base of the timber prop so it doesn't slip as they raise the prop.

https://www.engineeringenotes.com/mining-technology/mine-supports/types-of-mine-supports-timber-iron-and-steel-rock-mechanics-mining-technology/51784

(b) Roof Height of 2.5 to 4.5 m:

There are two methods:

(i) The position of the bottom end of the prop on the floor corresponding to the place in the roof to be supported is marked by a plumb bob suspended by a bamboo. The prop is held upright by 2 or 3 timber helpers. The timber man standing on a high stool or a ladder places the lid and a wedge is hammered on a position.

(ii) The above method requires a stool or a ladder to be carried from place to place for prop erection. The more convenient method is- a lid is attached to the prop by nails and a hole is made nearly 25mm deep in the floor where the bottom end of the prop is to remain after erection. The prop, laid on the floor with the bottom end in the hole, is made upright, the hole preventing the prop from slipping.

The prop is held in position by timber helpers’ and one timber helper levers up its bottom end by a crowbar bringing the lid in contact with the roof. A wedge is then hammered between the prop and the floor to tighten the lid against the roof.

 
pollinator
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Following this thread as my goal is to one day have a wofati/Oehler style house for ‘retirement’... even seems like the wife is starting to buy in a bit more and talking about some rural land being a good idea that she supports. Planning to stay in Missouri, but move further South towards the Ozarks/Springfield area eventually and would love to get some permie neighbors. I was wondering though, if I can plant or find a lot of black locust, how much would that change thinking about rot-resistance of posts?
 
paul wheaton
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Black locust will be far more rot resistant.  At the same time, you are in an area with more rot.  

I suspect that I would probably skip the treatment with black locust.
 
Graham Chiu
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Here's a video of a Korean hanok construction.  They also place the posts on stone.

https://www.youtube.com/watch?v=IPhAPa8wlCQ

At 2:40 they drop the post onto the stone support which looks like it's covered in salt presumably to give more friction, and stop water creeping up the wood?
You'll note the absence of rebar to hold the post in place!

Unclear as to what is happening at the end of the video.  Looks like they deconstructing the brick walls.  Maybe the builder was a cowboy as the information with the video suggests?
 
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I just mix a nice cob with lots of straw or woodchips and poor in hole around post. Works great in my climate.(desert/mountain). Also experimenting with cob foundations .
 
steward
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For all those that still need an answer to the old question: "how to prevent wood posts from rotting without using bad substances?', here is an answer from Paul, in the form of a cute video. Enjoy!

         
 
master gardener
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That's a great little video! Clear, concise and made total sense to me, living in a ecosystem that can rot just about anything in the wet winters we have! The little project I want to do will be difficult to build a 5 ft eve for, but using slope and rocks as a intercept might be enough to slow down the rot process acceptably, as it isn't a house.
 
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Would charring the postal before encasing them in crushed rock further extend  the life? Or is it entirely unnecessary?
I've become a char crazed wood worker of late and have no aversion to charring the wood prior to construction if it will help extend post life or strength through case hardening.
Overall. Lov9ng the simplicity of simply filling hole with crushed rock
 
Rocket Scientist
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Planting black locust is a long-term proposition. It will probably be at least 20 years before you have large enough heartwood for structural purposes. The sapwood (most recent several years of growth) does rot fairly quickly in moist conditions. That said, I would always advise starting some if you don't have any, as it will be useful for smaller projects within 10 years, and will sucker and coppice readily to make a perennial source of dense firewood for an RMH.
 
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