freestyle pallet+cob in an excavated area?

hi all. my plan was originally to put up 40"×48" pallets/posts in a 12 sided regular polygon and cob over that. but from a lot of what i've read on cob, the idea of just starting the walls at the boundaries of my excavated area may work? a lot of what is at the base of the pit is bedrock. mostly large basalt rocks. after the frame and walls are up, i would then level the floors and engineer a living ceiling and install any interior beams to keep the roof up. has anyone done any freestyle cob building like this with long term success? i will most likely continue with the original plan to do a geometric regular 12 sided structure with either a reciprocal roof framed out of lumber or a 6 sided hub approx 3 ft in diameter of an outer circle to meet corners of the walls at 2:1. any thoughts or guidance is appreciated!
stem walls will be dry fit stone with mortar

it's a 16'×16' square hole. realized i never mentioned that 🙃

Hi Savana;
The only thing I know about cob is building rocket mass heaters.
But I do know a thing or two about building in general.

So it looks like you are in a forested area that probably gets a fair amount of rain?
A stone stem wall sounds like a good start.
A 12-sided circle sounds pretty cool.
I would be sure to have plenty of roof overhang as well as good drainage away from the building on the high side.
A bedrock floor that I assume will be an earthen floor?
Hopefully, you are planning to build your rocket mass heater simultaneously!

Sounds like an interesting build!
Please keep us updated with plenty of photos!

thanks Rob... it seems like a lot of natural building is "experimental" which is exciting. i have several ideas that i would like to execute in this build. this will be a structure intended only for 5 years or so of low maintenance living... but who knows. it may prove to be a rather robust building. a lot of the cob mixes will be experimental. i am particularly interested in doing a mixture for at least one of the walls with a relatively high amount of charcoal, and plastering with a relatively high amount of wood ash to see how it helps deal with the high rainfall. the drainage system unfortunately will follow a traditional french drain system (perforated 4" plastic pipe with gravel and landscape fabric) our glacier runoff and rainwater is incredible and slightly alkaline. i am hoping to have a catch basin setup where i can get some good water storage as well.

yes! the rocket heater will be built with the structure and i will be building a hotplate griddle into it, as well as a brick oven chamber. i am wondering if the rocket heater will be more effective on the end of the house that is less underground or more underground. perhaps you can provide some expertise here.

thanks for the feedback and words of encouragement. this project started with me flattening a small 6' area for a tent, to leveling a small 16x16' hole, to having it excavated and i am now learning some stone masonry and other building techniques along the way! i am hoping to get a new computer so that i can create a 3D design file for this using solidworks (or possibly tinkering with Fusion 360 by Autodesk). either way, i am going to make sure whatever i decide to live in for the next few years will hold up and be safe. then i can share anything new i learn with the greater community and possibly help some friends build some cheap/beautiful dwellings on the land 😊

Hi Savannah;  Tom here.
Brother Rob moved on a few years ago.

I think with a cob house and thick walls it will not matter what side of the house your on.
As long as your chimney goes straight up thru the roof your golden.

You might look into Matt Walkers' tiny cook stove plans here is a link   https://walkerstoves.com/index.html
With that, you get an oven and a cooktop and you can heat a bench "mass" with it as well.

Or at the RMH forum, we can guide you towards building your own.

Keep us posted this sounds like an interesting build your doing!

thomas rubino wrote:Hi Savannah;  Tom here.
Brother Rob moved on a few years ago.

d'oh i am truly a space cadet sometimes. i meant to say... thank you Tom! i will check the link out right now! i think that if i asked for custom design help with the cob oven... someone might get pissed when i completely turn the design on its head. i have a problem with authority and following instructions (it's why i was never good at baking i suppose). 🙃 bad jokes aside. i truly appreciate the encouragement you've provided in your responses. i think it's got me in the mindset of "f*** it, let's do it, and whatever will be, will be" so for better or worse.. i'll keep y'all posted as the project progresses. should be fun, or at the very least entertaining and frightening. unfortunately, i have to work this project in sprints (currently consumed by corporate travel work... i know big suck, but it helps me financially fuel myself and my community) so it'll likely be a stint of a few days of lots of physical work, then weeks of planning, rinse & repeat. one day, i'd like to just build full time, but i have a lot of skills to cultivate and polish before then 😊

thanks again and take care!

Savannah, welcome to the forum!

I can't help with pallets and cob other than to say earth and wood are not a good mix due to rot.

The fellow is building similar to you so you might get some hints from this thread:

https://permies.com/t/180629/Hobbit-Home-Progress

Plastic pallets are available and may suit your purpose.
I have extensive experience with cob.
Feww questions;
- how is water to be kept away?
- can the rocks lying around be incorporated?
- the soil pictured does not look good for cob, what are your plans?