Questions about Balecob walls

I am planning on building myself a little cob house this coming spring/summer up here in Fort Collins, CO (Zone 5b). I have a couple questions for anyone with expertise regarding building with balecob walls.

1) My home will be about 300 "sq ft", and am going to build a Rocket Mass Heater as my heat source. In my design, it sits on the north side of the circular room, the cob thermal mass bench contouring to the curve of the room. I recently kinda decided that it would be wise to build the north walls of the house with balecob. Where I live, we get around 300 sunny days per year(!), but the winters can get pretty cold. My question is whether or not it matters what kind of material the wall is made out of that the RMH sits on. If i have a balecob wall, is that a squandered opportunity to have more thermal mass in the wall itself, or is the thermal mass of the RMH pretty much all contained within the cob bench?

2) Can balecob walls be load bearing? The house will be two stories, so would a balecob wall be structurally insufficient for holding up the second story plus roof with winter snows? I guess a partner question to that would be how to fasten and secure floor joists and roof rafters into the balecob wall?

3) And if someone could point me to some good resources regarding building balecob walls that would be awesome. (like making the walls curved, how to cob over them/how much cob, how to join the two building materials).

Thanks so much!

Balecob, anyone?

Hi Mitch,

I don't think you are being over looked, as much as folks may not know how to start to answer as some may not approve, or be out of their element. I will do my best...

I am planning on building myself a little cob house this coming spring/summer up here in Fort Collins, CO (Zone 5b). I have a couple questions for anyone with expertise regarding building with balecob walls.

I do not claim to be an expert in "balecob" as this is another "new-age" term for but one more version of "earth architecture" or better know in the English speaking world as "cob." Alteration to the material matrix does not change it from being "cob," (though it has many names and permutations.)

My question is whether or not it matters what kind of material the wall is made out of that the RMH sits on.

Not really, but that is a loaded question with many different answers...one depending on you skill sets as architectraul designer and what advanced skill sets you have as a builder of earth based vernacular forms.

If i have a balecob wall, is that a squandered opportunity to have more thermal mass in the wall itself, or is the thermal mass of the RMH pretty much all contained within the cob bench?

Having a "thermal resistance layer outside the "air condition envelope" is always a good idea. Adding a "thermal mass" to store energy inside the "air conditioned envelope" is a good idea. Now with that said it will all depend on how you design the wall and on which side you place the SB, where you place the thicker cob render, and other factors as well.

2) Can balecob walls be load bearing?

If you have advanced architectural skills, can do PE level load calculations, then have at it. I do not, and I can do both, ever recommend load bearing wall only supported by cob or SB, unless I am facilitating an authentic rebuild of some vernacular form of earth architecture. Even among the traditional vernacular forms, the most enduring and longest last (safest) have an internal structural system of some form.

The house will be two stories, so would a balecob wall be structurally insufficient for holding up the second story plus roof with winter snows?

See previous answer...

I guess a partner question to that would be how to fasten and secure floor joists and roof rafters into the balecob wall?

If you don't know this, you have answered you own question, "Can balecob walls be load bearing?" In your case I would say absolutely not unless you hire professional help...sorry but I have to as a professional. I am seeing way to many "owner builders" designing and facilitating architecture way outside their skill sets. One tectonic event or alteration to design and there are going to be problems.

3) And if someone could point me to some good resources regarding building balecob walls that would be awesome. (like making the walls curved, how to cob over them/how much cob, how to join the two building materials).

Gosh Mitch there are so many books I would rather see you read first on just basic building modalities and architecture, but any of the cob, natural, vernacular build-design books will get you going. You really need to develop some foundational skill sets and perhaps take a courses or do some "modeling" before such an ambitious project...or get some help from those that have at least 10 years of experience building in earth methodologies.

Sorry these reads like such a downer, but perhaps your next round of questions I can sounded more upbeat?

Regards,

j

Timber frame with bale cob infill is stronger and easier--you can build your roof first to help keep the bales dry during construction.

You can make the inside cob thicker by the RMH to be extra storage and thinner in other areas. That could be the backrest of the bench or it could be the whole wall.

Jay C. White Cloud wrote:Hi Mitch,

I don't think you are being over looked, as much as folks may not know how to start to answer as some may not approve, or be out of their element. I will do my best...

I wasn't trying to force an answer out of anyone, but still I do appreciate your response.

I have just noticed that I haven't come across any straw bale/cob hybrid buildings that are more than one story without any form of internal structure. (which of course is almost an answer in and of itself) But even so, I was hoping to glean some information from people who have building experience with this hybrid sort of method. I am not discarding any other ideas, like using a timber frame structure, I am just trying to explore this one.