Roundwood timberframe strawbale

If anyone could give tips on how this can work I'm all ears.

So my wife and I are working on building a octodecagon (18 sided) roundwood timberframe house with a basement, and 2.5 floors, the standing timbers would be 3ft± in diameter the height of the timbers would 30ft±. I am trying to use little to no concrete at all and would like to have pointers on how to even setup the foundation given the shape it has. The sqft of the whole thing is 12,000+ with all floors combined with the basement alone being 3295sqft in size. I don't want a slab for the basement because I wanted to use stones to support the weight of the frame and have the floor of the basement be an earthen floor. Any info you need to help get a better picture just ask, I'm just hate asking a machine to give good advice thanks 😊

What an undertaking! The closest thing it reminds me of is the Sivananda Lodge in Quebec. It is featured in the book "serious straw bale" by Michel Bergeron and Paul Lacinski, though they did not do a basement, but it is colossal as well at 8,000 square feel I think. He didn't do round timber, but modified post and beam with squared beams. You might look into the build and see if you can't track down more info on it.

May I ask why strawbale for such a massive building? It will need heavy construction equipment, serious foundation work and extreme amount of pest proofing and plasterwork, but still is just straw after all. Have you thought about the SIRE wall?

Now that is an undertaking. Are you in the United States? If so what state? Many answers might be dependent on your location. My house is modest in size and three of them would fit on each floor of your proposed home. A structure of that size would require engineering in Oregon.

This might sound a bit  nosy and incredulous, but why this shape and design? And yes, without knowing about location, soils and climate
no firm suggestions are going to assist you.  

Have you seen Mike Droske's Texas round house build here? Not a strawbale, but intended cob infill (I don't think they're finished yet). That is 74 feet diameter although I don't think they have a basement. He had some problems getting the first layer lintels in position.... A nice youtube series of the build so far (start here)

Cristobal Cristo wrote:May I ask why strawbale for such a massive building? It will need heavy construction equipment, serious foundation work and extreme amount of pest proofing and plasterwork, but still is just straw after all. Have you thought about the SIRE wall?

I love strawbale because it has the best insulation value and it's easier to install, I wanted the construction of my house to be built by my family and anyone of the community to come build it. I have looked at SIRE wall construction and didn't want like that esthetic for my house for the exterior walls but thought of implementing some of it in the interior walls. I just want to know how i can exclude using concrete for the 18 roundwood timber pillars in the foundation and well as for the walls themselves.

Rico Loma wrote:This might sound a bit  nosy and incredulous, but why this shape and design? And yes, without knowing about location, soils and climate
no firm suggestions are going to assist you.  

Appreciate the question it's no offense to me at all. I designed the shape because it was the closest we could get to for a circle and because it became so big from the constant planning and editing the initial design was a load bearing strawbale home. The circle creates less wind resistance and i love the esthetic of its overall design, no one builds buildings like this and I like the idea of being different and the overall challenge.

Beginning to understand your choice of shape, thanks. Wood in general and roundwood specifically is a beautiful way to build in the forest.  But moving the largest logs and debarking  them all might be daunting for the most seasoned builder.  Would you consider a circular build that was piece -by -piece and easier for two people?  Cement block is a time honored style, many tradesmen are confiden in its applicability.
I have never tried this other method, but hyper adobe seems like a fascinating type of house construction, with some projects finished with 2-8 people.  

Overall, this method will perhaps be safer and more predictable
Masonry is almost fireproof, and having a lime finish on both sides will discourage insects and mold.  Just my 2 shillings, best of luck in all your endeavors sir

My apologies,  I used block building as a general form of masonry.  Hyper adobe uses soil with rocks gathered on site, that's the style you might entertain for your project

Machy,

I understand. I do not like SIRE wall look either and if I built it I would plaster it with one lime plaster coat like I did on my CEB house - looks gorgeous. I love the properties of SIRE wall.
You said it's easier to install. On a small scale potentially yes but when dealing with heavier/longer/deeper - challenges grow exponentially.

In a serious case of securing 3 ton vertical logs to the ground I would talk to a structural engineer, who may love concrete, but at the same time will provide some guidance that may be applied to your idea.

Please read this thread on Permies:

https://permies.com/t/113626/Straw-Bale-Don#928596

How will you overcome any wood rot on the logs in the ground?
Are logs that big hard to find?

Footings for a structure that large and tall, without concrete, would need some careful engineering of properly placed and compacted large rock. If you wanted the posts to be stable through ground placement, they would need to be something like 6' or more deep below the basement floor. It would be considerably simpler to stabilize them with the rest of the structure tied together with diagonals.

With some information about your soil, subsoil and bedrock composition, and your climate, we could give some rudimentary ideas about the structure. You will absolutely need competent professional engineering advice before you start actually building, or you risk overlooking or underestimating something important that could be dangerous at such a scale.

I don't know why you would need 3' diameter timbers, even at 30' high, unless the wood was exceptionally weak or a few timbers were supporting the whole structure. If you just want a colossal look, fine. In that case, there would be plenty of scope for lots of mortised joints for floors and braces without impacting the strength of the posts.

I would caution that if you are putting beams between those posts, it will be extremely difficult to move the posts around to get both ends tenoned into the posts. You might have to resort to a lot of lap joints cut into the sides of the posts, which will probably not look as nice as properly mortised joints.

You say you want to use "stones" to support the frame. I think your best bet would be a single boulder under each post with the post bottoms scribed to the boulders. I think making a template or copy of the boulder top after placement to fit the post to would be the best way of managing that. This would start you with a stable base for the posts.

What kind of rock is available in your area? You would likely need one several feet across to support the post without sinking into the subsoil.

Glenn  and  Christo certainly describe some things to consider. Again, describing your location, soil composition,  etc will help these two masters of the craft advise you.
Is this your first project using 30' tall posts? We're they about 3 tons each?  And the boulders might weigh the same to support the posts, to prevent movement after placement.  Keep it safe, we can't lose any Permie folks, for the good of all ma ,ind.  

......of all mankind.......

I was thinking about the foundation. All traditional timber/half timber buildings were built on stone foundation - the base plate would be laid on the stone and structure attached with proper joinery. Stones would provide good anchoring and protect from moisture (no capillary effect, especially if laid on lime mortar). Building diameter of 20 m would equal very large medieval towers and they had 3 m+ thick walls. For building this size, stone foundation walls of 1 m thickness would be probably an absolute/compromising minimum - already 250-300 tons of material. Even if the isolated footings were used, the basement still needs a wall and continuous round foundation would provide very strong support.

From https://sirewall.com/the-sirewall-system/
SIREWALL stands for Structural Insulated Rammed Earth wall. It is a complete wall system used in modern rammed earth buildings that are energy efficient, sustainable and as strong as concrete

This may sound like a broken record, sorry,  but he is still a smash hit, platinum status....please consult our friend Mr Chickadee.
Their work is common sense yet phenomenal,  see the stellar timber framing , Japanese style.  

The scale of course is  smaller, but he demonstrates an ancient and proven technique.  But i could propose,' well Gulliver can you learn a skill or two from the Lilliputians? '
Here's one shot of the foundation details with selectively charred wood.

Machine, when you have time, those of the curious kind are asking for climate, soil, tectonics, log choices ,
...specifics , if you can supply please

Machy,  no disrespect, this #%!!/<#×@# autocorrect