cordwood, rubble trench, slipform

Hello alll! Hope someone can answer this question. Im building a cordwood home, timber frame cordwood infill, and im considering the rubble trench method for the footing. Everything that i have read says to put a concrette grade beam on top of the trench but these are generally refering to strawbale or cob homes. Im building a stone slipform stem wall and i wonder why would i need a concrette grade beam between the rubble trench and the stem wall. could i not build the stem wall directly on top of the rubble trench. Like i said I havent been able to find any info on the specific combination of building techniques that im using.

it seems to me the terminology may be wrong. there's a lot of confusion about what to call what when it comes to foundations.

instead of a grade beam, maybe it's really a footing they're thinking of. it is wider than the stem/foundation wall in order to distribute the loads better. i think you could also form this with stone, but i'm sure that's the reason. Plus it provides more contact friction with the rubble.

Joe,my limited understanding is that the (reinforced)concrete grade beam is used to distribute the load( as Suki wrote)which I presume is the roof load...
but if you are having a timber frame structure you have taken care of the majority of the load...your walls are not then load-bearing so I would think that you would not need the grade beam.
There is a great forum for cordwood with many experienced minds contributing...www.daycreek.com
I'm sure they could easily answer this quandry.
Where are you building your home?
All the best
Kate

Doh! Wasn't paying attention about the timber framing. in that case, Kate would be right. And calling it a grade beam would be right.

But I would still put in a grade beam. It ties the timber footings together, should be rebarred together, which helps keep the building to move as one should there be an earthquake. I don't know if you live in an earthquake zone or not.

Im building in N.W. Arkansas. Thanks for the Quick reply

Thanks for the Quick reply

He he. On vacation and in the permie honeymoon phase - will slow down as soon as I go back to work!

You might want to check about the seismic zones. I think Missouri was the epicenter of the largest quake in N.American history, which would affect NE Arkansas. Don't know how that impacts NW. Arkansas.

my answer has been nagging me because it was confusing, due to addressing two different subjects in one answer. hope i didn't steer you wrong.

my understanding is the rubble trench foundation is for a monolithic building to float/rock on, while the grade beam/footing foundation is all tied together monolithically for the frame to be secured to.

i don't think mixing the two systems is advisable.

in either case, you should have something continuous under your stem wall..

lots of gas fracking quakes out there now, make sure the thing floats as a whole.....

I am guessing the grade beam gives you;
-  a flat surface to start with c.w. with a rubble surface
- an edge board around the walls to kick instead of the cord wood or stones
- and if needed a hard surface to install hold down bolts or wires right through the structure to the roof.