How to protect untreated wood posts for 200 years?

I saw some guys on Youtube that were building a wilderness cabin and they were sticking the ends of all the logs into a fire to char them real good as a way to keep them
from rotting I presume.    I never saw that before....    Does anyone know how much if at all this practice is helpful to the longevity of the logs ?

I t would help. For sure.

But, it would depend on the dampness of the ground, the soil composition, wood species, the quality of the char, and what sort of ground the pole was planted in, and if there is vegetation growing against it.  

The things that rot or deteriorate the pole are going to be bacteria and fungi, mosses and lichens, or ants or termites, depending on what the local scene is.  

Most poles will rot out at or near the point of contact with the soil.  I've seen fences made from 100 year old fire killed western red cedar.  That is where they rotted.  

It sort of falls into the 'edge effect' phenomenon.  There is more diversity two different climates meet than in either of the two climates would have as added individuals.  

So, where air meets soil, where soil meets wood, where soil moisture meets wood, where plant moisture meets wood... that area usually rots first.  Reducing those factors, while using a more rot resistant or dense wood might be a major factor as well as planting the poles in rockier or sandier soil rather than silty or clayey soil is bound to have a more favorable condition.    

My experiences:  black locust wasn't really worth cutting and putting in, ( i didn't peel them and I heard that would have helped.)  We have cedar posts that have been in fences for 70+ years that are coming to the end of their useful life.  We have some osage orange corners we will dig out or pull up if we can and replace just because they are too short for the fences we are building now and I would look like an idiot to stretch a new fence from posts that were put in almost a century ago.  I'm in a dryer climate than many of you though.

I have tried charging on my raised beds. So far, so good.  I really don't have a big enough sample..nor have they been in place long enough.

I also wondered a lot about this, how to use wood for posts in the ground in a way that is more like a permaculture approach. Paul came up with an answer for us:

I grew up in Central Illinois with a fairly wet and humid climate.  There were fence posts all around us that were as old as time (honestly, I would not be surprised if the fence posts were put in around the turn of the 20th century).  Those posts looked positively ancient when I was a kid but they were absolutely rock solid.  Actually, they appeared to be outlasting the barbed wire they held.

Those posts are still in the ground today with new barbed wire.  All the posts are made of Osage Orange and while they look horribly ancient, they are still rock solid.

I don’t think you can beat an Osage Orange branch pounded into the ground.

Eric

Jp Wagner wrote: A treatment for humid conditions can be easily formulated with a glycol/borate solution.

You don't want bor in your soil...or wood....someone 50 or 100 years down the road might also be tempted to use the posts for hugelculture
or something and bor is really bad for your health.

Travis Johnson wrote:Sitting on rotted posts, the weight of it kept the building pressed on the soil and over the years as the wood rotted away it just settled lower. the building did not move, look out of place, or ruined, it was just a lot shorter in headroom. Theoretically a WOFATI with adequate headroom could do likewise with no issue for many years..

But practically a wofati has earth on the sides or is even built on a hillside. The forces on wofati do not apply right from above like in a free standing building.
Oehler himself described a situation where the whole building just slid some inches down the slope.
Imagine what would happen when the bottom of the posts was rotten! Plus there is a huge weight on the roof!

As of Pauls solution, i am no earth-working engineer, but i can imagine that tampered earth is more firm on the post than gravel.
If you use gravel, make sure its crushed, not round, so that the edges interlock with each other.
Anyways i would be interested what an engieer says to this approach, remember that the nice thing about the Oehler book is,
that is has a section with exact measurements that have been approved by an engineer so that an amateur can use it wihtout harming anyone.

So speaking of Oehler, he had quite an interesting suggestion on how to seal the posts in a environment friendly manner:
When using a regular oven, there is black stuff accumulating in the chimney (pitch?) and the farmers would have used that
stuff to seal their fence-posts. Really an excellent way of recycling waste!

Probaly the birch pitch approach would be the closest one to this, as it is difficult to find anough of those chimney residue for
building a wofati, especially when people around you only use RMH which burn the stuff

The best example I have come across addressing this exact construction issue is the classic Stave Church of Norway. The principle is simple - do not let wood come into contact with soil at all. Water will leech and decay almost anything over time, so the best technique is to keep water separated from dry goods completely. What we see here is a classic Stave Church elevated on a foundation of dry stacked rock, which is the longest-lasting stone technique because mortar can also potentially deteriorate. These churches are now in the 800-year-old range because of this practice. They are maintained by coating the wood with pitch as needed, which makes most sense as this is applying like to like - the pitch came from the tree in the first place. It provides a perfect resin coating to keep the structure as dry as possible. Moisture is everywhere, it's just a matter of conducting it per the dictates of the individual climate. Working with nature as opposed to trying to beat it back, which never works long-term.

It probably rains a good amount in Norway, so fighting moisture is a losing battle, you just have to separate your materials out in a way that keeps them preserved. Stone conducts water down and away, wood supported by stone is elevated and removed from direct contact with water, therefore there is no opportunity for water to spend any real time with the wood. Ambient moisture and rain is inevitable anywhere, so the application of the resin acts as a highly effective mitigator of temporary contact with water from above. Again, conducting it down and away. the whole affair uses only natural materials, and is really the simplest way of shaping nature to suit human needs. I suspect these churches were inspired by Pagodas on someone's trade journey at some point lost to history, because of their multi-tiered roofing style and the minimalist approach to construction. In a modern sensibility I suppose you could add interior cobb or stucko walls and concrete or terazzo floors etc if you wanted extra insulation and refinement on the interior.

I once planted naturally sourced-branches from English Laurel as fence posts. I made sure to fill the bottom of the post holes with concrete before putting in the posts, then filling more concrete in around them and stacking the concrete above soil level the make a sort of incline away from the post, thus providing something of a 'sealing' and 'repelling' technique. The posts were variegated and bendy which gave a really cool effect, and I suspect they will last 50-100 years before the concrete deteriorates and the bottoms of the posts rot out, but that was fine for that project. If I wanted to make something truly legendary, I just simply would not put any wood into the ground under any circumstances. There is no technique that will stand the test of time besides keeping wood and soil separated completely. And the best material for fencing is actually just dry stacked stone. Nothing to deteriorate at all.

I've often wondered about ancient earth homes, i'm assuming which are stacked stone with soil and sod over the top. How does the moisture soaking through stay out of the interior open space? I suppose the initial stack of the stones can be done in an angles way to guide the water to flow down and away, but this would really have to be done well to work fully wouldn't it? They did it so it must have worked. I have seen open-air stacked stone huts done this way, so the rain getting in must be minimal, except for the smoke hole for the fire.

I personally think conducting water down and away is the first concern for any building project. Water is a wonderful thing, so directing it and collecting it is my primary thought when envisioning an earth home. I love soil too, but it seems that stone, in some form and application needs to provide a solid barrier from soil in order to make a dry space. Even backfilling thick concrete walls with soil is not a great idea in my opinion. I would use sand and gravel, and have a really good drain system put in. The constant moisture contained in soil is too much for anything to withstand for a truly long or even indefinite period of time.

I have a very old barn on my property, its about 50'x70' and 3 stories tall, built out of trees, all axe cut.  there are no saw marks on any of the trees that make up this barn. its got to be at least 100 years old. the ground is mostly wet clay soil.
the vertical trees on outside edges are all sunk in the ground I'm pretty sure they are all red cedar. but the interior vertical support poles are all on pedestals of rocks and cement that is crowned and grooved so no water can stand on base of poles if water does get to them.