Tree stumps as porch foundations

I'm looking at land, and one of the potential sites has a lot of little trees in the flat area where I'd want to build a yurt.  I would need to clear those out.  I also would need to then put in a bunch of poles to support the porch/base of the yurt.

Can I just saw the trees off at the level I want the porch to be and use the still-living stumps as the porch piers?  I figure established root systems would be a helpful anchor.  I also figure maybe they'd rot and the whole house would come down.  

Rob,

That’s a very interesting idea.  My initial hesitation revolves around what happens to those stumps in the future—what keeps them from rotting away?  I don’t doubt that an established root system will hold solidly, I just don’t know how the roots or trunk will remain solid after all the foliage is gone.

Food for thought,

Eric

Hi Rob;
I agree with Eric.  Those small stumps will die and rot. Might take a few years but it will happen.
I recommend small concrete pier blocks  partially buried  and set your posts on them.  Concrete never rots and posts are super easy to replace.

I can tell you that my mother purchased a house in the 60' s that had to be at least 50 years old. It was in central Illinois.  When I crawled under it, I realized it had been sitting on tree stumps.  The house is still standing.  I have no idea what species of tree the stumps were from. And, of course, your mileage may vary.

A big enough tree, completely covered by the house. I would expect it to last 50 -100 years.
Little trees exposed to the weather just would not last in the long game.
If Robs yurt is a 5-10 year temporary structure, then they might last.
I guess small concrete piers could be installed a few years from now, when the stumps start to fail.

thomas rubino wrote:A big enough tree, completely covered by the house. I would expect it to last 50 -100 years.
Little trees exposed to the weather just would not last in the long game.
If Robs yurt is a 5-10 year temporary structure, then they might last.
I guess small concrete piers could be installed a few years from now, when the stumps start to fail.

My thoughts exactly. The ideal setup for blacksmiths back in the day was to cut down a tree for the anvil base and build the shop around it. As long as it was kept dry, it should last a lifetime. I would add that I think it worth while to bore holes and add plenty of borax if you want it to last as long as possible.

Tree stumps were used in building many years ago.  Many of those homes still exist and the stumps work perfectly well if made out of the right wood.

Here is a thread that might offer some suggestions:

https://permies.com/t/18698/tree-stumps-foundation


Our first home's foundation had what we call "bodark posts" aka "Bois d'arc" aka Osage Orange.

Here is an article about that wood:

https://en.wikipedia.org/wiki/Maclura_pomifera




Black Locust would be another good choice:

https://permies.com/t/4078/Black-Locust




Cedar would be another option.






I feel everyone has given you some great advice, this is just another answer to your question.

I will add that using cut down live trees as stumps may present a problem as they might sprout new limbs making the stumps to become bushes, unless something was done to kill them.

Just a synthesis of the answers...

1 ) species of wood matters a lot.  If its on the list of rot resistant trees, then that's a good start.

2) shelter matters.  An exposed trunk will rot, but the larger the dry space the better.

and I'd add ... soil moisture matters.  Keeping the exposed trunk dry is great, but if there is moisture in the ground then the stump will rot from below.  So consider slope, and it might be important to add a drain trench around the perimeter.

So ... a yurt.  The space under the yurt will be dry, but all the stumps towards the edge will be more exposed and will rot. Since a yurt isn't that big, a lot of the stumps (maybe all?) would count as being "towards the edge" and thus at risk.   And any exterior decking won't protect stumps under it.

Excellent comments above. As noted, moisture from above or below creates the conditions for failure.

The "holdfast" portion of most trees is incredibly tough. It takes the bulk of the torque from wind stress. I can see putting a semi-permanent structure on them.
 
My thoughts:
- Make note of other old trees of the same species in the area. Is there evidence of carpenter ants or termites? That would be a caution sign, both for structural issues and unwanted visitors.

- Debark the stumps (and any other cross members) to encourage curing and discourage decomposers.

- Build a base/deck that is structurally sound in itself, sitting on the stumps to keep it off the ground. That way you can jack it up, level it, move it, or supplement the tree foundations as needed.

If you do this, we want pictures!

Wow, these are great answers everyone.  Thank you.  I have a lot of thoughts to think now.

Definitely will post pictures if this happens months from now.  :)

The plot I was looking at was I think maple and oak.  But I did not truly take time to verify.  I just remember the bark.

Great idea. I just had the same idea a few minutes ago and then searched to see if anybody had tried it. I imagine this was typical way back but lost favour to modern methods.

I live in Mongolia with my Mongolian wife. I'm originally from the UK. We're probably going to buy some land (about 1400m/2) that is forested with mostly Siberian larch. Apparently this is a naturally rot resistant species. We will probably build a ger platform on the land since it's a south-west facing downhill (about 9 degrees) lot. There are a lot of trees we'd need to cut anyway. Why not use the stumps, I thought, and the lumber for decking. This could save a ton of money since lumber prices have gone sky high due to covid and border closures. We'll first need a container for secure storage - gers (yurts) are not in the slightest bit secure - and that will need a leveling method. Then a ger (yurt) platform for 1-2 gers. If the first project is successful, then we can move forward with the platform for gers. Next year we'll probably build a simple house with SIP's which is pretty light too.

One tip I saw for posts in the ground, is to soak motor-oil mixed with diesel into the wood, then let it dry then coat with roofing asphalt. This won't help below ground but it could help to minimize water absorption above ground. Especially on the naked stump face. Mongolia has a dry climate so I'd expect the stumps to outlive me (I'm 58).

Let us know of your progress and I'll do likewise!

Local knowledge is very valuable, particurly since not many of us have Mongolian experience!

Thanks for the reply John C Daley. I'm trying to learn from the locals but traditionally they put the gers (local name for yurts) directly on the ground in river valleys and moved them several times a year, so they weren't ever concerned with foundations. In recent years, they just learned from the Soviets and that meant concrete. I don't want to excavate a beautiful virgin hillside in the forest, even for footings.

So, I'm considering alternatives. Possibly steel ground screws which have little soil impact. Or tree stumps and also I can use the lumber. A lumber platform for a couple of gers would be semi-permanent and could be moved or disassembled for rebuilding if the pilings (stumps or steel) settle or shift. The 3rd stage would be to build a lightweight house. I took early retirement so I can work on these projects full-time.