Building a cob home

[rathbone]

Yaaaaaay You! It looks amazing. Truly, truly amazing!

 

[soulmatenlove]

We finished the gable ends with the loft dutch doors. And we called the inspector for our final. Hopefully, we will hear back from him soon.
In the meantime, we are contemplating on the insulation for the cob home. This weekend we are heading to a sheep farm to purchase a bag of raw wool. My thought is to use some old wool blankets, wash them in borox, cut them to rafter size and stuff with the raw wool, BUT my DH thinks that this idea is impossible. Too many blankets are needed, but we did have a friend donate 5 of them, so we only need 2 more. We could probably find these at the local thift store.
Now the only other problem is how to deal witht he vapour barrier...is it still necessary.

 

[rathbone]

I like the blanket idea. I would never have thought of that.

 

[Marianne]

Where do you think you need a vapor barrier?

I was under the assumption that it's more important for the cob to breathe...now, where's my book?

 

[StupidBird]

I find your project awesome.

Years ago I drug DH and the little DS's to a very hippie-style cob workshop in a secretive (due to zoning) commune-like project in rural somewhere. It was our first live intro to self-sufficiency, organics, vegan, etc. My poor city boy DH was overwhelmed, but accepting. The cob cabins and workshops and shed-like buildings were great. Little boys LOVE stomping up the cob and slapping it into place on walls - and on each other. It showed me that cob was a suitable material for the humid SE US.

More details on getting building permits and what you used to "educate" the inspection folks, please. More photos, I'm greeeeedy!

eta: cattail fluff from the bloom ends was used during ww as insulation and life jacket filler; called kapoke/kapote? (but when I google it all I get is some tropical tree, and a paper on using cattail fluff to clean oil spills)

 

[soulmatenlove]

Where do you think you need a vapor barrier?

I was under the assumption that it's more important for the cob to breathe...now, where's my book?

The vapor barrier is not going on the cob walls. The vapour barrier is going to be used in the rafters, the warm side. We will probably use a 6 mil plastic. Although we did come across a classified ad for a bubble foil from a local florist. The R-value is appoximately 2. My soulmate thinks we should use this instead of the plastic as it can reflect heat back into the room.

 

[soulmatenlove]

More details on getting building permits and what you used to "educate" the inspection folks, please. More photos, I'm greeeeedy!

We may have gotten lucky with the building dept. The town we live in is a small community and the regulations here aren't enforced with an iron fist. But more importantly the building is permitted as a "shed". We had designed the building to be just under the minimum square footage to where a building permit wouldn't be required. But upon the building inspectors initial visit, he informed us we were slightly larger than the minimum. We made it clear we weren't about to pay for an engineer to draw up some plans, and really didn't want to pay for the building permit at all. Also, we told him if this was going to be the issue, we'll just shave a few feet off the building. He then told us the permit would cost about $50, and that because the building is so small, a simple floor plan and a cross section detail is all that was needed for the building plans. We took this as a green light that we shouldn't have any problems with the building department. As far as any information regarding using cob as a building material, he seemed to already be familiar with it. He even mentioned that he and his wife were going to build their own home using cordwood.

So in our particular case, we had a few things going for us. The building inspector (aka plans examiner, aka chief building official) is pro-building green. The building itself is small and, shall I say, insignificant when compared to a house. Lastly, we live in a small town where the 'community' includes the people who hold municipal jobs, and we all work together.

 

[Marianne]

Where do you think you need a vapor barrier?

I was under the assumption that it's more important for the cob to breathe...now, where's my book?

The vapor barrier is not going on the cob walls. The vapour barrier is going to be used in the rafters, the warm side. We will probably use a 6 mil plastic. Although we did come across a classified ad for a bubble foil from a local florist. The R-value is appoximately 2. My soulmate thinks we should use this instead of the plastic as it can reflect heat back into the room.

Do standard construction builders use vapor barriers in the rafters in your area? Here that's a huge NO NO - condensation! But I'm in Kansas, your area may be completely different.

 

[soulmatenlove]

Where do you think you need a vapor barrier?

I was under the assumption that it's more important for the cob to breathe...now, where's my book?

The vapor barrier is not going on the cob walls. The vapour barrier is going to be used in the rafters, the warm side. We will probably use a 6 mil plastic. Although we did come across a classified ad for a bubble foil from a local florist. The R-value is appoximately 2. My soulmate thinks we should use this instead of the plastic as it can reflect heat back into the room.

Do standard construction builders use vapor barriers in the rafters in your area? Here that's a huge NO NO - condensation! But I'm in Kansas, your area may be completely different.

This applies to the cold climate where I live, in Northern Canada. Hot climates are another matter.

There are several reasons for wanting to keep the warm air inside the house through a vapor barrier installation; among them:
1.Energy efficiency
2.Heating costs
3.Preventing the deterioration of the building materials (wood, insulation) by moisture (hence the alternate term moisture barrier). In winter, as the heated air meets the cold air, it creates condensation, which is water of course. The vapor barrier is designed to prevent this phenomenom from taking place.
4.Health problems caused by molds

 

[the_whingnut]

Cool thread and love the set up. I got to see several cob buildings in England and Scotland that were over a few hundred years old. Not to mention the emperor's tomb in china is also cob. We had planned on doing a small building to start then doing the big stuff I'm think stupid big like earthship style.