Post in ground techniques

For pole structures, I've heard several techniques to overcome the problems associated with burying part the post in the ground, but each seems to have its own problems

1) treated post - obvious problem of toxicity

2) new Oehler technique of charring the bottom and wrapping it in a bunch of garbage bags. - Doesn't seem to hold up for many people, Paul suggests that it is because the moisture in the wood has no place to escape.

3) Black Locust wood - Sounds great, but many people like me don't have Black Locust trees.

4) Pack surrounding earth with diatomaceous earth and borax - I heard Paul suggest this idea and I like it but I would still be concerned about moisture/bugs from the ground getting to the wood.


5) I have an idea of using some kind of bottomless barrier like a 5 gallon bucket with the bottom cut off or something probably deeper, packing that with dry, sandy dirt, so the moisture from the wood can escape, and mixing it with diatomaceous earth and borax. Also using the charred post.

Do you think this makes sense? Are there any other suggestions out there?

I have given some thought to a similiar idea. After seeing pressure treated wood rot after 3 years in a subgrade sandbox I would question any woods ability to survive packed in sand. Initially I thought the sand held moisture against the wood but the dryness leads me to believe that the sand dried the wood out. I think a 5 gallon bucket set with the lip above the grade and the bottom below the frost line is a good starting point for a post foundation. What about filling the bucket with 57 stone? I also gave some thought to putting a hose in the bottom of the bucket so that i could siphon out any water that collected. It may be easier to just a hole, pour concrete and set post on a post base anchored in the concrete. but a 5gallon bucket foundation certainly sounds awesome.

Packed sand in a clay posthole is a waterbucket in the wet and a saltbox in the dry. The wood doesn't stand a chance.

Is it possible to not to bury the posts?
If so, You can try to fill some used car tires with sand and build pole structure on them.
Something like in this video http://www.youtube.com/watch?v=CdFv0lV83iI]http://www.youtube.com/watch?v=CdFv0lV83iI[/youtube] at 0:18

Or there is the old school method i described in this post: https://permies.com/forums/posts/list/40/4738#138193

We use juniper and chestnut posts around here. They take a long time to break down.

I thought you might like to see a Corsican solution to your problem. That post in the foreground is granite. I saw whole fields fenced with dozens of these things. I can't imagine the work that went into making them, but I suppose it's a pretty long term solution.

Corsica fencepost

Would it work to put the bottom of the post in a drum in the ground, and fill the drum with gravel? Would this compromise the structural strength of the post? Would the gravel keep the wood happy?

i've been wondering about this same thing. and reading about related ideas.
but with the plastic bags, or rather some kind of plastic sheeting and then fill that with some kind of soil crete or soil cement? ash? wood ash? thats what i was just looking up, and soil cement.

how well it would work with bags/plastic sheeting and then fill in with some kind of soil cement, sand + gravel? and ? ash? with a kind of watery soil cement being poured in and tamped down.

i am having this idea about wood ashes, so i have been talking to google about that.. wood ashes and making soil cement. it keeps seeming like a good idea somehow, even though i havent found that much info on it. i am going to try it and put some ashes in a soil cement mix that i am making for some fence posts.

it would be cool to make a kind of soil cement, without actual cement.
or something like that. as it is you can stretch a few bags of cement really far with the soil cement.

i've also been thinking about very thin and long holes for posts, filling in the long thin (barely bigger than the post) hole with some sand/gravel- then coating wet soil cement onto the post and pushing it in, as it went down would that compact the soil cement pretty well? then dropping dry fine particles of soil /cement from the top so that it would work into any small gaps.

well thats my basic plan anyway, but this is for a fence not a post for a structure.
temporary is ok, if it last for a long while. but i wonder about the plastic sheeting bags idea, and if that would be better or would work.

borax also sounds like a good idea.

Has anyone considered biodiesel? It's supposed to be an excellent wood treatment. You could treat the ends of your posts the same way Mr. Oehler originally treated his with penta, i.e. stand your post up in a half-buried 55 gal. drum filed with biodiesel and let them soak it up for a day or 2.

Try sharpening the bottom end of your posts, like a nail is sharpened. It is the sharpened tip of the post that holds it up!

You might try smearing/painting roof repair (thin the tar with diesel, add kreosote or whatever) on the buried length of the post.

If all you have is oak, white is probably better than red or black oak posts!...just clean off all the bark & sapwood first, let it dry a couple years if you can, or use right away if you painted the bottom with tar.

james beam;)

hey that seems like a good idea, even if unfortunately it uses some purchased and less eco friendly stuff.
i think thats kinda the deal here, seems to me anyway the only way to protect the wood if its in contact with ground is to use some intense harsh stuff.
well plus the burning, which is an excellent idea. i already burnt all the ends of the tan oak posts i am using.

had to look up creosote. its something i heard before, sort of knew what it is- but i wanted to know exactly what its made of-
http://en.wikipedia.org/wiki/Creosote

this to me basically confirms my intuition about the wood ash. its come to me as a good idea, and i think its sound.
i started thinking it would be cool to use a TON of ashes in an earthen mix, and for posts...that it would help a lot....
and that maybe the way to start some kind of construction would be to have an enormous bon fire in the spot where you were going to build.

there would be a lot of ash around and could be mixed in...and besides you could make friends a bit with the fire spirits perhaps!
appease them somewhat and request they leave your structure alone =)
even if this has no effect, it certainly cant hurt to try, and anywho its a nice blessing ritual, and you get some ashes to build with.
so i did that, in a small way, had a fire where i am working and gathered the small amount of ashes i had from burning the posts added them to some wood stove ash.....

though probably "creosote" you can purchase is refined more, and probably from coal (?) - maybe more effective-
wood ash and "creosote" from my wood stove is what i have a lot of right here.

i also think theres some part of a can of that tar roofing stuff around...i wouldnt buy it fresh, but i will hunt for it and use it. theres also roofing tar paper...i had been thinking to work that in there too, i might.

like if in that top drawing, instead of plastic- the roofing paper lining the hole.
then fill that in with a little clay/gravel/cement or mortar mix of some kind with lime/little sand/and lots of ash
o and borax.
biodiesel is an idea, or linseed oil?? its kinda expensive....and dont have any oil around. or bio diesel...but i would try that....

on a totally different note the best idea i have had about this is to use LIVING TREES instead of posts. its ...sort of hard to work out the specifics of this, but living trees dont rot.
i have visioned some interesting structure, walls, and supports for small houses, using living trees for structural integrity.
some how...using a lot of rocks and some kind s of half wall at their base...made of earthen stuff and mostly rocks/sand
at the base of the tree, and training them to grow in certain ways, even bending them over and pleaching them.

Hey Leila, thanks for the nice reply...very interesting to check out your website & pixs.

I just threw in that roofing tar thing for fun, yanno there might be some extra roofing tar buckets a person might scavenge from around town, like you said Leila, heck I found nearly 2 gallons of the stuff this year~~I know I'm rich, I just can't seem to lay my hands on it~~ The kreosote (coal oil) thing definitely works: telephone poles & RXR ties have the coal oil smell with a thick black tar impregnated into the wood, I was just going for a homemade smear-on attempt at rot & insect prevention.

I haven't tried the charred end posts yet, but it sounds great too me... except for the extra handling from the post charcoalized processing, and I'm guessing you have to water quench the charred ends to make the burning stop at the proper penetration...sigh, I remind myself how lazy I can be.

Leila, your tight fitting post hole idea should work in your dirt, especially if you can get the clay/ash/concrete liquid to completely fill the voids & set well, perhaps put the liquid in the hole first, then nail the post in (isn't that what you said) It is common practice to pour dry sakcrete around the post, tamp, then pour some water on it to make it set. But my example here is rocky, gravelly, and rocky, with no expense of sakcrete, so I have to dig out the hole just bigger than the post, but with room enough to jab a heavy iron rod thru to the bottom of the hole, push in what dirt is found & pack the bottom tight. Push in remainder, jab the rocks and all as tight as possible, tamp the top of the filled hole and on to the next. Also if your chopping thru solid sandstone, that heavy bar is used to chop the bottom of the hole to resemble the bottom of your post, therefore the sharpened tip or square cut post will stick well into a properly fitted hole in rock. Bottom line is: the bottom or sharpened tip of the post must be completely tight in order for the post to stand on its own.

james beam

hey everyone. im a first time poster, but i read about underground cabins a couple of weeks ago. didnt use posts but buik
lt traditioal 9x9 wrapped in tarps and he treated the wood ;like you would a pine/oak desk. painted the barked wood with polyurothane( cant sspell). wouldnt that protect it along with the plastic? As for drainage, the logs were horizontal so just build up a 18 inch platform at each corner leving an area underneath for drainage. he laid a tarp over the four platforms and under he wood floor the protect from moisture and insects.

james beam wrote:Hey Leila, thanks for the nice reply...very interesting to check out your website & pixs.

hey -thanks for noticing me =) and being kind =)

james beam wrote:
I just threw in that roofing tar thing for fun, yanno there might be some extra roofing tar buckets a person might scavenge from around town, like you said Leila, heck I found nearly 2 gallons of the stuff this year~~I know I'm rich, I just can't seem to lay my hands on it~~ The kreosote (coal oil) thing definitely works: telephone poles & RXR ties have the coal oil smell with a thick black tar impregnated into the wood, I was just going for a homemade smear-on attempt at rot & insect prevention.

I haven't tried the charred end posts yet, but it sounds great too me... except for the extra handling from the post charcoalized processing, and I'm guessing you have to water quench the charred ends to make the burning stop at the proper penetration...sigh, I remind myself how lazy I can be.

yeah couldnt find it. did find some but it had all dried out. but i think youre right, that stuff could be salavaged. theres got to be thousands of half empty cans of that stuff somewhere.

james beam wrote:
Leila, your tight fitting post hole idea should work in your dirt, especially if you can get the clay/ash/concrete liquid to completely fill the voids & set well, perhaps put the liquid in the hole first, then nail the post in (isn't that what you said) It is common practice to pour dry sakcrete around the post, tamp, then pour some water on it to make it set. But my example here is rocky, gravelly, and rocky, with no expense of sakcrete, so I have to dig out the hole just bigger than the post, but with room enough to jab a heavy iron rod thru to the bottom of the hole, push in what dirt is found & pack the bottom tight. Push in remainder, jab the rocks and all as tight as possible, tamp the top of the filled hole and on to the next.

yeah thats pretty much what i did. except it wasnt quite so orderly as that, but some wet, then dry, then wet- and mixing more and more as i was getting close to the bottom, so very random mixtures and amounts of ash/clay soil/bag crete/gravel and sand. though...it was approx the same, and i found using less soil to lots of bag crete was working out better. but yeah wet, then dry, then wet, dry and rinse and then repeat =)

with lots of different sessions of tamping and adding more dry, tamping again.
i do have a nice big heavy rod for making holes, so thats interesting that you wrote that out- that was my main tool for the job besides my shovel.
and my feet of course =)

something like that, and my soil crete came out pretty good and the posts seem solid. i was not neccessarily going for permanant...though long term would be good. i ended up not using anything, around the wood, but did burn all of the ends. in a different sit i think i would have used some wood preservative type stuff or a half empty can of whatever kind of sealer. or even just buying those premade freshy cement blocks the are so handy for something like this.

started thinking about empty space...like in relation to this. it seems kinda odd at first ...the idea seems to always be that you must pack everything so tight- but seems like in some kind of project like this some kind of empty air space...ah well thats the idea i just started having.
i attached some metal to the bottom of the posts, not the proper things you would buy for this, but different kinds of metal L shaped pieces. i feel that they helped.

hey kerri ann, welcome ~~~ I like the idea of a tarp wrapped around the logs, your tarp leaves a 9" dead air space which has got to help with the insulation value of the floor logs. They seal mobile homes in a similar 'dead air space', with a real thick heavy 'tarp', no fiberglass, just 'dead air'.

Since you already painted the logs with poly, OHHHH man you have to get that off of there quick~~~hahahaha just joking~~~ its gotta be just fine!

The oldest log floor I've seen was very old, and those old logs still had most of the bark on em after a hundred years. The old timers might of painted it with oil or something, hard to tell now, still in good shape, whoever put the logs in the house only hewn(chopped) one flat side, of which to nail the floor-boards too. I think the trick to make that log floor last so long was to get em off the ground like your 18" you mentioned, and then keep a non-leaky roof over them, they will dry out rock hard...eventually. It is common practice to use a piece of sheet metal on the top of the pier, but your tarp should give the bugs a barrier between the piers & your logs.

james beam;)

hey Leila, heck ya 'air space' is possible, now that ya got me thinking of it. so why couldn't you just pound a 2' length of 3/4" rebar round steel in the ground, yanno pound it about a foot deep. Then drill the end of your post with a big 3/4" auger also about a foot deep, and set it upon the driven rebar. I could even imagine getting alittle fancy and placing a flat metal or plastic washer to inhibit moisture wicking up the post from the dirt (like a pie plate, or an recycled aluminum can). Heck if you needed your post super sturdy you could drive a 3' piece of rebar 2' in the dirt and pilot your post onto it. Hummph I may have to try this on a fence project, cuz yanno my back is already broke from digging too dang much rock! Driving a stake seems easier.

Leila hope you will forgive me, rebar & drilled post really isn't 'air-space technology', give me another hint!

james beam

well no, thats about the same idea i was having to create the space...using some kind of metal...even nails/screws put in all over at weird angles....to create the space around it in the bottom and sides.

i think the roofing paper thing i was thinking of...would also have the effect of creating a little bit of empty space in there, then you would have to make it soild and stable too (which would be what the metal and such would be doing hopefully)....

ah well just a bit of a brianstorm not sure how well it would work out in actuality. but got me thinking....like in a tipi...they use that empty space idea....well totally different kind of idea there...but thats part of the thought. seems like the space would allow the moisture a place to go and work itself out...basically....

that the issue is the direct contact between the wood and ground (or the contact of wood and cement) and thats its all put in there too tightly...which exasperates the moisture issues...and that empty space...would somehow allow the moisture to be sowrked out....without being trapped in the wood....

I just posted this in a similar thread, but since it directly applies, here goes:

How about replacing some support posts with something like a metal pipe filled with concrete? This would get rid of some of the risk of rotting columns, and their high strength is well known and documented in building engineering. I know the cost is more than free logs from the forest, but it may be worth it to avoid future problems.
I know it's not as attractive as big logs, but I have used them for supporting framing members/beams in a basement before. (paint can do wonders, or you can box them in with 4 boards to make a simple fake column)
Since this is a well-known construction component primarily used in basement or commercial construction you should be able to get support and components easily. The only downside is you may need to get access to someone who can do welding or steel pipe cutting.

Alternatively:
The other thread also mentioned treating the ground contact area of the wooden posts with epoxy. Would that not seal in the wood from moisture? Here's yet another idea: capping the ends with large PVC pipe a little larger than the log end long enough to stick up above the ground and filling the gap with epoxy, making one connected plastic cap? This would be less toxic in the long run, though I don't know if you can get large enough pipe and caps easily.

Very good thread here! I have been thinking lately of a mud brick/adobe/cob solution to post footings. Anyone have experience with that?

I still feel like there must be some way to put a wood post in the ground without treating it with some kind of grossness...

I wonder if Mike Oehler's garbage bag technique would work if there were channels for air ventilation? Or would this just speed the rotting process by providing oxygen the sunken post?

Any thoughts?

I would avoid any wood touching soil like the plague. A rubble trench foundation, or anything that raises the wood above ground level is indicated here IMHO. Without a good foundation, any post and beam stucture will eat itself from the inside out. Large stones set in gravel, sono tubes filled with concrete, culverts set on upright and then filled with a coarse draining material and capped with flat stone, etc.

I have to agree with Tom and the general direction of this thread. Unless its a very short term structure, avoid wood touching earth. Wood that touches earth will become soil, its just a question of time.

Moisture speeds the process and most of what has been described here is only a delay tactic. Climate and site conditions can have a big impact on longevity. In the pacific northwest and east of the Mississippi (wet and humid climates) "post in ground" should probably be avoided altogether.

I know there are examples where it has been done successfully but most long lasting timber is separated from the ground by masonry and even better; separate the wood from the masonry. In my opinion, its not any harder (or less permies-like) than coming up with ways to treat the wood for ground contact. Most building codes agree.

If this works..

"Bottom of footing below frost depth"... If you are talking about a living space that will be kept above freezing, you don't actually even need to worry about that. There is a mainstream alternative technique to avoid deep footings for structures that need them only for frost resistance. It has been rigorously tested and is in specs for some big building group, I forget which (it has been a decade or more since I researched it). Essentially, you dig down 1 foot or so and run styrofoam down the outside of the slab with reinforced thickened edge, then horizontally with a slight slope to drain water away from the building. The horizontal styrofoam is just as effective as running the same amount vertically down a foundation wall, with the added benefit that frost pressure never gets near the foundation.

Of course, this is only relevant to the exposed side of an earth-sheltered type of house, but could be beneficial there.

What causes wood to rot? Is it bacteria? So, if it's bacteria, then I would guess they need moisture. If they need moisture do they need a certain threshold? Or are "they" different in their moisture needs? If we could get a post with, say, 20% moisture would it last a long time? What about 15%? Is moisture the main component that stimulates the deterioration of wood? what about temperature? I'd like to learn more about the rotting process so I can approach possible solutions with a bit more knowledge.

Also, does anyone here know why cedar, cypress, black locust rot so slowly?

brian that looks very interesting. Could you put holes in the metal plate to let the post breathe?

Anyone ever think about our old friend salt? Borate salts are used as a less toxic wood preservation with good effect, and wood structures in salt water last a long time if it not for those worms.
I'm taking dry posts and soaking them in a salt and boric acid solution and then letting them re-season at which time I plan coat the part to be buried with a water proofing of some type, maybe tar.
The exposed portions will be coated with paint, shellack or varnish, all helping to keep moisture out of the wood.
It may take a few years to give any data as to success or not.

David

what about salt? can it be mixed into the cement? can you use it to bag fill the hole mixed with concrete with like 30lbs of it up against the wood so that the wood absorbs it... salt is a preservative and nothing that i know of lives in the salt flats...

Please find this drawing to illustrate what Paul is asking the ants to do. Adding salt to the borax may be a future decision.

People around here use car tire rims in exposed hunting watches and have lasted over 15 years. Another option is a old fashion fence post holder or rocks like someone else on the forum said. All of these work with the knowledge that posts always rot at the surface.

Eric Grenier wrote:posts always rot at the surface.

Thank you.

Thank you, I'll clarify my question. Can a whoffati be made without digging in the posts? This would eliminate the major problem in this design.

Eric Grenier wrote:Thank you, I'll clarify my question. Can a whoffati be made without digging in the posts? This would eliminate the major problem in this design.

You would trade one problem (rot) for a collection of other problems.

The wofati design is such that if you put poles in the ground, you can tremendous stability, plus strength. The trick is rot. By eliminating 99.999% of the moisture to the poles, that eliminates nearly all of the rot. A little borax gives a little extra insurance.

Too many subjects, I missed this one.

This is a PROVEN solution that is adopted by the International Building Code for Post-Frame construction in all climates an soils.

Minimum footing frost depth in Missoula is 42 inches: this is to avoid frost heave, which is very real. The hole needs to be bigger than the pole by three inches or more all the way around. The bottom of the hole should be soaked over night with some water, but not a lot. the next day when the water is gone and the dirt isn't sloppy, the bottom of the hole should be compacted with a tamper/pole to where it does not compact the dirt any more (bounces).

NFBA and USDA both indicate a big rock or concrete pad (4 x 8 x 8 solid cmu) be placed in the bottom of the excavation/hole. In the drawing this is below 42 inches just to be safe. Once the pole (no bark) has been set into the hole, crushed gravel (clean, no fines) is placed around the pole. The gravel is placed in lifts of about 4 to 6 inches and a 2x4 tamp is used to compact it into place while the pole is kept in alignment. Place gravel to the top.

DO NOT PUT CONCRETE AROUND THE POLE...it will trap the water and cause rot.

I don't know how 'green' it is but painting the hidden part of the pole liberally with creosote is popular and has worked for railroad ties for a century or more.

My experience for post setting that may be relevant was in virginia where termites are to be found everywhere. I needed a temporary shed and figured I could salvage the fiberglass roofing panels easily enough so I did not greatly worry about longevity of the posts. I cut down 4 likely small pines and used a draw knife to strip off the bark. I had leftover crushed rock from the drain field and I dug holes for the posts about 2.5 feet deep in the red clay soil and put a foot of crushed rock in the bottom of the holes. I then stood the sappy "green" pine post in the hole and filled the hole around the post with crushed rock. Note that I said crushed rock and not gravel. The angular nature of crushed rock will cause it to lock together whereas rounded gravel will slip. I No sooner had I filled the holes to the top with crushed rock around the posts than they were as solid as if set in hardened concrete. I then built a frame for the roofing panels on the top of the poles.
A. The poles had a sump under them for water to drain into.
B. The crushed rock would not hold water against the sides of the posts.
C. the slope of the surrounding ground provided for drainage
D. The roof directed water away from the posts.

5.5 years later when we left the posts were as solid as ever. 10 years after that when I was again in the area, they were still there and solid.

For what it is worth, that is my account.

Ty Morrison wrote:Too many subjects, I missed this one.

This is a PROVEN solution that is adopted by the International Building Code for Post-Frame construction in all climates an soils.

Minimum footing frost depth in Missoula is 42 inches: this is to avoid frost heave, which is very real. The hole needs to be bigger than the pole by three inches or more all the way around. The bottom of the hole should be soaked over night with some water, but not a lot. the next day when the water is gone and the dirt isn't sloppy, the bottom of the hole should be compacted with a tamper/pole to where it does not compact the dirt any more (bounces).

NFBA and USDA both indicate a big rock or concrete pad (4 x 8 x 8 solid cmu) be placed in the bottom of the excavation/hole. In the drawing this is below 42 inches just to be safe. Once the pole (no bark) has been set into the hole, crushed gravel (clean, no fines) is placed around the pole. The gravel is placed in lifts of about 4 to 6 inches and a 2x4 tamp is used to compact it into place while the pole is kept in alignment. Place gravel to the top.

DO NOT PUT CONCRETE AROUND THE POLE...it will trap the water and cause rot.

I don't know how 'green' it is but painting the hidden part of the pole liberally with creosote is popular and has worked for railroad ties for a century or more.

The solution Ty and Don propose makes the most sense to me.

I'm figuring out if I can build a Mike Oehler underground house that will conform to building regulations here in the UK. I'm struggling to find any reference to the gravel technique being approved by any codes - any pointers anyone?

If it doesn't fly with building regulations I'll have to investigate placing the posts on plinths and adapting the frame to compensate for the support lost.

Here's another handy pic:

I've been looking into this issue myself. I found an advertisement for a post protector boot that you put your post into before burying it. They say it lets the wood wick the moisture out (up the post inside of the boot) and it keeps bugs and rot from attacking the post. It's approved for uplift situations (pole sheds) and was used by a national park on signage posts and they're happy with it. It can be used on non-treated wood and is guaranteed that the wood underground will outlast the wood above ground. They're pretty affordable so I bought some for my next project. I plan to take lots of photos and do a summary of the results. Since I saw this thread I figured I'd pass it along in advance if it would help people out.

They don't have a website

If you call/email them they'll send you the full brochure.

SmartPost
1-888-519-5746
smartpost.postsaverusa@gmail.com

We did what Ty and Don outlined when we built a 6' fence in Westcliffe, CO. Because this was to enclose a 1 acre site and because we are not spring chickens, we paid a crew with a small machine to auger the post holes 8" in diameter and 4'- 5' deep. We then put 3/4" angular rock (gravel) in the bottom of the holes and placed the 10' tall, 4x4 cedar posts in them. We then added gravel and tamped 4-6" lifts of gravel into the holes, keeping the posts centered. The fence has held up beautifully for 10+ years. It was one helluva lot of work, but it was worth it.

There are now precast concrete embedment post bases. This example is pretty straightforward. Seems to me, that these could be site-made with Simpson Post Anchors, rebar down the lentgth, set in a form and three sacks of concrete.

http://products.midwestpermacolumn.com/viewitems/perma-columns/six-foot-perma-column

These seem like pretty high carbon-footprint solution. At the end of the day, we have many examples of well drained wood posts standing for generations.

I also have read about a Norwegian technique that chars the end of the post increasing natural resistant to rot.

how about a post that is freshly cut wood, plant it like you would a cutting, let it grow roots. Trim any branches that interfere with the structure but essentially let the "cutting" live. Sure it will put on girth over time (very little if you don't allow it to have many leaves) but it won't put on height if you prune effectively.