Please Help me Design a Tiny Cob Home :)

Hello People... I have been lurking on this site and have posted a few times. Researching Natural building for a few years now and have come to the design stage of my little Dream Home. Background. I live in the Rainforests of Far North Queensland Australia. It does not get cold here... 40-105. I can speak in metric or imperial but will use imperial as much as I can due to the large community of people from the United States of America on here. On average we get 13-15 feet of rain per year where I live. Mostly during our Summer from November through till May. Wet Season. Our dry season also can receive a lot of rain but nowhere near as much and the temps drop. So I believe Cob to be the build of choice for me.
  I have already done soil testing and will post some pics on here if this thread develops any interest. Heavy clay content and I will have to bring in sand aggregate for the build. It is a rainforest on an ancient hillside so I will also have to get rock trucked in. I have a fantastic quarry nearby with good quality blue granite in any size I need delivered to my property at a reasonable price. I will be getting a backhoe into my property to cut a pad for the build and also to ferry the rock, gravel and aggregate from the place where the truck is able to dump the rock. The pad is at the top of a very steep concrete driveway nestled in the forest. The driveway continues up the hill about 700-800 of low range only 4 x 4 on a very rugged road to my council approved house. I will be living in my house whilst all of this is going on so it is not a rushed job. I just would like to live in a toxin free space. I already have a 24v Stand-a-lone solar system, Composting toilet and 5000 gallon rain water tank.
  So that is a bit of background on where why and how. What I really need to ask anybody on this forum who would like to Join in on my virtual build on permies is... What would be a simple yet efficient design. My backhoe operator is very interested in my idea and would like to do as much as he can whilst I have his machine on the property. Including the rubble trench. So for now I need to get a floor plan designed for the stemwall. My current vision is for a 200 square foot dwelling. I would like a loft bedroom but am having difficulties working out how that can be incorporated into a small building. I am thinking a reciprocal living roof but am open to anything that will fit the build. Cold is not an issue and neither is privacy. I will have no neighbours where the Cob home will be. The site itself is situated on the south side of a hill. So during winter our sun is far to the north. Not too radical a change but enough to be a problem for my current solar system during the middle of winter on the south side of a hill. There are some beautiful large trees including figs that I will be leaving as the area is a part of my property that is well protected from cyclones and I trust the large trees :) rather than fell them. One has to go but a ceremony will be done for it. In the last 12 years we have had a cat 4 and a genuine cat 5 right where I live so I know it is protected as it is the only place with many large trees left on it. Apparently botanically it is a pygmy forest due to the sheer volume of large cyclones that seem to really like my little part of the world. Near Mission Beach if you want to look it up.
   The Majority of the build will be done by me. I have looked into buying  second hand mortar mixer but I also have two neighbours I am friends with who own kubota tractors with buckets on the front. Lucky me :) I could possibly run a work shop later on but am not relying on that. I am fit. Early riser. Reformed drinker and smoker and have time to do this. And the will!! As I have said I am not locked into any particular design and would love to have input from others about the outcome. Single room. Verandah area could be made using recycled corrugated iron which I have access to plenty of. An interesting thing that I have collected for a later use is 7 panes of tempered double glazed glass. Each piece is 6.5 foot by 3 foot. They were given to me as they were a whoops the sliding glass door frame built into the house is 4 inches too small.. My gain.! I would love to somehow incorporate one, two or more into the build as I do not have privacy issues. i dont have a single curtain in my current house. Mosquito and bugs screens will be essential however. Its a forest and any light attracts all sorts of different critters. Anyway this is a rough outline of what I would like to do. I have read as much as I can handle... I have the Hand Sculpted House... Will be seeking much advice from a cob builder 120 miles north of me. Have asked advice from numerous people including some fantastic peeps that may well frequent this site. If I lived in the USA I would gladly go to a course and gladly pay some Dollars to the right people to teach and mentor my build. But I live in a sort of remote part of the Queensland coast where this sort of stuff does not go on. My time line for beginning the foundations is the end of March. Possibly earlier. Chris my backhoe dude is waiting for me to give hime the go ahead. Right now we are in the middle of the Big Wet (torrential rain) so i have about a month to get the the floor plan for the rubble trench sorted. Look forward to hearing from anyone on here that is interested in helping a human create a tiny little dream home. In'Lac'ech :)
 Todd Hunter

Hi Todd, this sounds like a great project, in an amazing location. If you get the opportunity to take photos you should definitely start posting those to this forum so we can follow your progress.

Having the hand sculpted house is definitely the best next thing to having taken a cob course so you are all set there. With that book in hand you should have all the technical foundation, wall, and roof information you need. Just make sure your rubble trench drains to light with that much rain. 200 square feet is a great size for a first time build, and with curved walls will be fine for a reciprocal roof. If you want to incorporate those big windows into the design, you will most likely need a straighter wall so that it will fit. The shape should really be decided on to fit organically into your surroundings.  Feel free to check out my blog. The link is in my signature. I also recommend checking out the following links that are to smaller cob houses like yours and give some nice info, one is even in Australia.

https://earthenacres.wordpress.com/2010/02/

http://www.diyhousebuilding.com/cob-building-henry6.html

Thanks for those links mate... Will start posting some photos when the rain stops :) ...

Hello,

If I have some spare time I may draw up a sketch to get you started.  A few questions to get me started.  How thick were you thinking of making the walls?  How high were you thinking of making the? Do you know what type of lumber you would be using for the reciprocal roof?   How deep does a rubble trench foundation need to be in your neck of the woods?  Do you know the grade of the hill you are building on?  Do you have a flat spot for your home or will it be cut into the grade?

Mauro Pacitto wrote:Hello,

If I have some spare time I may draw up a sketch to get you started.  A few questions to get me started.  How thick were you thinking of making the walls?  How high were you thinking of making the? Do you know what type of lumber you would be using for the reciprocal roof?   How deep does a rubble trench foundation need to be in your neck of the woods?  Do you know the grade of the hill you are building on?  Do you have a flat spot for your home or will it be cut into the grade?

 Hi Steve and any others Watching... We have just had about 3-4 foot of rain in the last week, so it has taken me a while to get some decent photos. The site will be levelled using a large Case Backhoe. The photo shows the size of the pad that will be cut. All up about 24 foot diameter and 15-16 foot diameter for the 200 sqft home. I am thinking 24 inches wide and 24 inches deep for the rubble trench. There is no frost issues where i live. It simply does not get cold enough! I will be using Blue granite for the stem wall and for the rubble trench itself with gravel 1 to 2 inches. This material will be taken to the site with the backhoe as a truck is unable to get into my property on the driveway. To the right of the pad in the photo there is a good drainage area and a drainage trench from the rubble trench will be going into that. I plan on a composting toilet and shower outside of the house. So the walls I think would be 20 inches thick. I am not sure what height they will be as I am unsure of the final layout of the home. I really do not know where to start regarding installing a loft bed. Double or queens size to save on floor space. If it is easier to just have one on the floor then that is fine. Simplicity is best as this is my first build. The reason I asked for help was to get a floor plan ready so that when the backhoe is here he can dig the foundation trench at the same time as clearing the pad and moving the rock. The ground is pretty hard down in the sub soil area and would rather the majority be done when he is here. Any corners I can dig myself but would prefer to have the longer portions dug by machine.
 The photos of the bricks!! I am pretty sure that I have a heavy clay content in the subsoil. The jar is at six weeks not and has not really changed much and has a lot of clay in suspension. The bricks were left for 5 weeks and may be too thin for the 5 foot drop test i did. All of them exploded on the concrete from 5 feet. The percentages and fractions were a clay soil to aggregate mix. Personally i believe the 60/40 was the best mix. No straw was in there.
 Regarding the Lumber... I have a large tree behind my Completed house that needs to come out in the next month or so. Semi hardwood that may well process some good lengths of lumber. I am not yet sure. I also have two other trees on the building site that will need to come down as well. I am hoping they too may be of good use. I will have a mobile mill to do the job as he takes wood as part payment.
  So the basic floor layout for the rubble trench is the most important for the moment as I will need to have something for the Operator to go on ... Simplicity is key for me. Of course quirky and cute is also highly desired. Hope this helps and I really appreciate any help offered and received. Will continue reading and researching design.
ps... as a side not. I would really like to incorporate some of the glass panels I have in the build. Ventilation is also key as it will be in a humid and hot rainforest.
Cheers... Todd

Have you already begun your foundation?
We decided to go with a 7 meter rondaval made with cob and a reciprocal roof. Even at that size we needed to create a bump out for the bathroom, shower and closet. We still made it too small once we realized things we need to store. Even here in Mexico it gets colder in the winter so blankets, jackets & rainboots have no home. Brooms, buckets & mops. Forget storing tools and this is with the kitchen in another rondaval same size. There are two of us & hubby  has way too many musical instruments. Just saying you may want to look at what you own first and make sure there is a home for all of it in your design.
Enjoy the process!
Holly

I ask why does a tree need to come down, when you could move the house?
More importantly, your soil needs about 50% sand and gravel, it appears to be about 100% clay which is unsatisfactory.

You may need to dig deeper or in a different area to find some sand etc.
Good luck

hey there todd.

looks like you are living the dream! how is your progress?
cob wants to be about 10-20% clay the rest can be up to 30% silt and fine sands the rest ought to be crunchy sand. lots of things can work, but building while the weather is wet means the walls wont set as fast and putting lots of cob on walls made with too many fines can make for instability and slumpage, worst case -wall failure. (scary af)

i live in about 300sqft with my partner and 2.5 kids. we have other out buildings for things that need storing and things that need washing like clothes and bodies. we make it work.
i would do 200-250sqft place. rounded north wall with nice doors heading out to the north and put a big overhang out there for shade, and extra dry space. this front bit could be single story and the hang out/eating area, the other 100sqft behind, could be two stories, the kitchen below, and bedroom above. out the back of the kitchen is more overhang where you can poop in a toilet and have a shower if it is not raining at the time!
6 posts, two roof planes. two short posts for the north side. (one beam to catch the front load of roof line 1) two tallest posts in the middle, (w/two beams) one can catch the high end of the single story roof the other beam catches the high end of the loft beginning roof plane 2. two more posts medium height to catch the back sloping roof of the loft. over all shape a big oval or an oval with one end squared up...

does that make any sense?

cob rockets built in the rain are my speciality.

now this house has a double loft. but you get the idea... it is also only 120sqft on the ground. more if you count lofts