Shell to pack cob?

I was curious about something. I am a beginner and have not even started mixing anything. 1st i know that i first need to go and test soil and try mixing all the samples to find the best mixture.
However im going to be building a smaller shed as a test before i start a house. The property im on already has about a 10x10 slab of concrete poured on it. And to get to the point i was curious if
you can build a wall shell and just drop the cob mix down in and pack it down at the top? Im thinking it wont work because from what i understand you have to pack it as you go. And im not sure if this will get all the air pockets out of the cob.

The shell does not have to be 8 foot tall would be nice if you could do that all at once. However i was thinking about a 2 to 3 foot section tall by 8 or 9 foot in length.

Do you think a that this would pack well and get air pockets out? The shell would be removed as soon as the cob was packed and set for a few hours.

Any help would be appreciated.

Thanks,
Tyler

Hello Tyler,

Welcome to Permies!

1st i know that i first need to go and test soil and try mixing all the samples to find the best mixture.

Yes you do and be patient and thorough about it. Test bricks of cob mix, or other clay matrix types are advisable as well.

However im going to be building a smaller shed as a test before i start a house.

That is a good thing to do.

The property im on already has about a 10x10 slab of concrete poured on it.

Make sure you put some type of "flashing" material between the concrete, and whatever sits on it.

i was curious if you can build a wall shell and just drop the cob mix down in and pack it down at the top?

No, that is not advisable for a number of reasons. It may seem simpler and like a "corner cut," but it is not. When ever doing any fashion of "lift work," it must be done in stages, whether rammed earth, or other infill modalities.

Im thinking it wont work because from what i understand you have to pack it as you go.

This is correct, and it has to do with firmness of packing as much as the potential for "air-pockets."

However i was thinking about a 2 to 3 foot section tall by 8 or 9 foot in length.

No, a full high wall to original design parameters is much better, and structurally stronger.

The shell would be removed as soon as the cob was packed and set for a few hours.

Each lift, depending on methodolgy (i.e. light clay chip, light clay straw, solid cobb, etc) will very in total height per lift depending on material density, and 'form support"" method. It must dry thoroughly before removing "form work," and any attempt at adding additional material to the wall assembly until the other material is dry, is not recommended at all. Cobb, and all its related building methods, always perform better with solid in framing work as the armature of the building over the use do just plan and pure cob.

Regards,

j

Thanks for you Response. I will test some bricks and see what happens.