If you do a google search - images - you can see some wall section details that show the foundations built out of "foundation stones" that go below the frost line.  Not sure if they are dry stacked or used some kind of mortar - If this is not for some historical research project you should use concrete for the foundation.  In addition, you should consult a structural engineer to figure out a way to reinforce the foundations and walls - otherwise you are building an unreinforced masonry building, if you are in an earthquake zone it is only a matter of time before failure - cosmetic or catastrophic.  I'm sure your local engineer is going to love working with adobe brick that does not have a listed compressive value.  

Unless of course you build the whole thing out of AdobeFoam™.

@chigurh

Thanks for responding.Foundation stones are usually used with mud mortar in rural areas and they are used dry as well.It is definitely not a historic research project but i was just figuring out a way to use only traditional materials and the site is not prone to earthquakes.It has dry climate with temperature reaching up to 40 deg.c during summer and moderate rainfall during rainy season.

And for reinforcement i was thinking of using bamboo/timber poles which are planted in the foundation at certain interval upto a certain height into the wall !?

i'll be using only local masons and hence I'm trying to use materials they are comfortable with.The work is happening through an architectural NGO so we are tight on budget as well:)

Coming back to your response.I think i'll do a wall module with foundation stones and mud mortar and check for strength.and yes i shall consult a structural engineer:)

Thanks.

Any conventional foundation system should work fine for adobe so long as the wall is fully supported - due to the relatively large width to height ratio of a normal adobe wall (less than 1:8) the compressive force on the foundation for a one story building will normally be less than 20psi, which is tiny (code normally prescribes adobe bricks to be at least 300 psi).  Preventing differential settlement is a bigger deal than just compressive strength - in most cases, you can get away with an engineered gravel trench foundation topped with a reinforced concrete grade beam.

For wall design, in non-seismic areas, take a look at the New Mexico Earthen Materials code for requirements.  For wall design in seismic areas, there are two approaches: 

1. Traditional Strength Approach, whereby vertical and horizontal reinforcing are added to the wall system to make up for adobes relatively low tensile strength.  This is the path favored by the US codes (IBC) but globally considered kinda backward since earthen materials don't bond well to rebar.
2. Stability Approach.  The idea here is not to strengthen the wall, but rather to make it more stable by preventing out of plane overturning/bending.  This is usually accomplished by wide walls, contained with wire mesh (such as tightly attached stucco mesh) or geotextile.  This work was pioneered at the Catholic University of Peru and is now becoming common outside the US.  Seismic forces are absorbed rather than resisted (walls are allowed to crack and remain in place).

If you are interested more in this topic, check out the proceedings from EarthUSA, or the Getty's Seismic adobe project, both of which are science based sources.  There is a lot of very bad information running around out there, some of it perpetuated by engineers who don't under

@Janosh

Thank you so much for taking time and responding.We did think about gravel trench foundation topped with reinforced concrete beam but the point is to use earthen materials only.So we discarded concrete beam.Now we are using granite boulders,coarse and fine aggregate with earth masonry for foundation.To reinforce walls we are using bamboo sticks planted  into the foundation at certain intervals up to the height of 5' from ground level(Local building technique).

We are building a module as of now to test its strength and durability.The site is non-seismic and one of the most dry areas of south india.

An.Ma - sounds good!  If you are in a non-seismic zone and walls have a height to thickness ratio of less than 8:1, its likely you don't even need vertical reinforcing so long as the roof is designed to act as a diaphragm (holding the top of  walls in position relative to one another).  You might check out the work of Nripal Adhikary with Abari (Nepal) and Lara Davis at Auroville. Both are working sort of in your region and have devised some simple but clever technics for earthen construction adapted to local climate and materials.

@Janosh

Thank you so much.Yes will definitely go through their works and i did refer Lara Davis's works while researching for this project.I'll be in Auroville for a while in summer.I'll be taking training in CSEB construction!

Are you from India?