Methods for putting timbers in the ground?

[Don P]

Grad students have been torching things and seeing what happens for a long time, look it up. Generally when you burn stuff the small broken molecules of burnt "goody" washes away with the next rain.

Bear in mind what extractives are... extractable. The universal solvent is... water. The tannins, the brown tea and a big fraction of the protection is certainly water soluble. Cedar bleed when finishing. The pine knots shined through the stain blocking finish yesterday, water based paint. Black locust, aka yellow locust makes a pretty yellow dye in the borate tank. All those extractives are water soluble.

The waxes, fats, sugars, starches are variously soluble in water or solvents, but those are food, not preservatives. Are we thinking a flash fire improves the oils and resins. If anything you are cracking the tar. Burn asphalt and tell me you've improved it. Is sugi simply a naturally decay resistant species used in mild conditions showing durability despite man's interventions?

The rods begin diffusing when the wood is above the fiber saturation point, that is when borate moves in , or out, of wood. By the time your rod in the middle of the timber sees FSP the vulnerable outside has been at rot levels of moisture for some time. Now the rod needs to dissolve and diffuse to the damp zone. IMO, too little too late but better than a poke in the eye. The RR association had good results with a borate followed by creosote process. The borate went deeper than the creosote and was protected by the water repellency of the  creosote. The last I saw of that they were at 25 years. That is on a gravel bed, it is not a real good sink to pull the borate. Think about the difference between "washing off" vs diffusion into something like soil for a better understanding there.

[Joe Hillmann]

I knew a guy who drilled a hole in the center of the post from the bottom up to above where ground level would be.  He filled the hole with used motor oil and pounded in a wooden plug to cap it.  Once the post was set he would drill hole about a foot above ground level and try to hit the hole that was already there and every time he did an oil change he would put the used oil in a oil can and go around and put oil into the holes on every post.  He swore by it that it made the posts last forever.

[Joe Hillmann]

When I make wooden bearings I repeatedly boil and cool the the chunk of wood in new motor oil.  When I heat it up air and water is driven out of the wood and bubbles, then it cools and that empty space in the wood sucks the oil deeper in.

I have a couple pieces of oil soaked red oak that were left overs from building my sawmill that got misplaced. They spent two years on the ground and I recently found them with the lawnmower.  They are in better shape than I would have expected (but I didn't have a piece of non oil soaked red oak buried next to it for the same amount of time to compare it to)  Maybe a similar method could be used on posts, with our without charring.  And MAYBE that would extend the live of it.  Or it may do nothing at all, or make it worse.  I have heard of gunstocks "rotting" out because of years of gun oil acclamation in areas that it couldn't be cleaned out of and the wood in that area getting soft and flexible from the oil.

[scsmith42]

I think there are a lot of variables for example how much charring on the wood, the species, thickness, location, base, rainfall, frost line, etc...

What will work for some might not work for others.

Again I'm not trying to discredit you but there are many upon many people using this method.  Eric Sloane's book Reverence For Wood mentions the same method.

Lots of information on youtube.

https://www.youtube.com/results?search_query=charred+timber+posts


Again my usage is a 16x8 shed for all my lawn maintenance stuff, etc... possibly a motorcycle.  I'm not talking about a timber framed home or anything.  I do appreciate all the feedback, and I am going forward with it . Not sure if I'm going to use 6x6 or 8x8 yet, still planning.

What you are missing in all of this discussion is that the charring is not what makes the wood last - it's the underlying species.  Ian addressed this in his response.
Simply charring a non rot-resistant species gains you little, if anything.

Several of the folks that have responded are highly respected experts in their fields, yet you are ignoring their very wise counsel in lieu of something that you 'read on the internet' but don't fully understand.
If you insist on going forward, then you will be more successful if you start with a very rot resistant species - such as black locust or some type of cedar for your posts.

[snobdds]

Dead wood is carbon.  How does carbon degrade?  Oxidation.  Water has 1 molecule of oxygen in it.  Remove the water and exposure to air and the post will not rot. 

I put posts in concrete that extends above grade.  It prevents water and air from getting at the wood.  Finish the concrete at the ground to shed the water from the post, all it needs is a gentle slop to shed water.  It will take longer than I'm alive to rot.