Earth Bagging in Central Vermont

Hi Folks! Newbie here with some questions about earthbagging in Vermont.

I understand that it is a very labor intensive process and I am prepared for that. I am planning on using hyper adobe with the Raschel bags that one can order from bagsupplies.ca
I would like to make an earthbag dome in the style that you don't have to angle them inwards to make a perfect half circle dome, but rather the pointy type.
My intent on building this dome is to cover it with earth, maybe 3 ft thick at the thinnest point.
A question I have is if it is possible at all to make a dome, 26' feet in diameter? I thought that you could only do that with a bag that when filled is 26" wide after being tamped? Also, how much do I have to corbel over the edge of the bottom layer to make the shape of the dome I am looking for? This is the calculator I have used that leaves me at odds with what I would like to do.

http://www.terra-form.org/tools/earthbagdomecalc.html

Also, would the 3+ feet of earth covering the dome keep the dome warm in the chilly Vermont winters? We have 48" of annual rainfall where I am located, what would be the best way to keep the water that soaks through the living roof, from permeating into my earthbags and leaking into the house? I have heard breathability is a must for earthbags. Someone mentioned putting a thin coat of bentonite clay on the bags themselves would be best. Any help on these questions would be greatly appreciated. Thank you so much my fellow earthbaggers! Sam

Hi Sam,
I love the work of Nadir Khalili and others who have built these beautiful structures, but look at the biomes they are designed for and look at your own. The most important design criteria for building a home is the biome where it is located. You live in a cool, damp place with lots of woods. People there in New England have traditionally used wood and straw more than clay and sand.
The design drawings that you posted are very beautiful, but more in line with desert living. Try to incorporate a timber frame and infill with natural materials and this home will blend into the landscape, while providing optimal shelter for you and yours.
Good luck and I look forward to seeing your design evolve.
Bill

What Bill said...x10...

The huge thermal mass means that in Dec when outside is 20F, inside will be 45F. because it is cooling slowly it will have the same temp as the soil. And once the soil in your farm is frozen and unworkable, Jan-March, so will all the dirt, your house will be at least 30F.

What all that means is that you will need some insulation. In the desert, even though the temp gets to 20F at night during the day it is back up to 55F. In new england the highest it gets to is 32F, so you are going to stay frozen.

But lets say you dont care about heat lost and you have 'unlimited' fuel. Will that massive 3ft thich building super saturated with water and ice be able to support itself.

I would instead recommend a earthbag (long or regular size) filled with perlite or rice hull. Then cap the structure with a post and beam supported roof. Make the roof super strong in Boston we just got about over 100 inches of snow in about 30 days.

Hello Sam,

I am about to write here almost verbatim what I have written before and again on another post just tonight...

I have been in, out, and around the architectural field for over 40 years now...I have watch many things develop and undermine good building habits of the past. I can't begin to write about the never ending drive of industry to make profit and the human drive to "reinvent." Sometimes great things comes of this...unfortunately, most is not, and some is actually just plain bad...I see most designs of modernity preparing humans for living in space as humans seem to bifurcate socially as a species with some only feeling comfortable in the country, while others are much more secure packed in shoulder to shoulder, wrapped in plastic, glass, concrete and steel. I am sure that when the time comes, we will launch a new age for our species as we reach for the stars...but...until then most of what we build today is but a glimmer of what our forbears achieved.

With that said, I would suggest to always look first to the vernacular architecture of a region that has centuries, if not millenia, behind application in good use. I would also humbly suggest that desire, drive, motivation and stubbornness can be powerful tools...These characteristics can also push folks in directions they ought not go. I watch in this current trend of "natural" and "new age" building with many wonderful..."ideas and concepts," but I must share that most folks have more drive and motivation than common sense and the necessary traditional building skill sets they should have to achieve what the "think" is a good idea. What I typically do with clients and students is ask a series of questions...if they can't answer those questions then it is most likely they are not ready to tackle whatever it is we may be discussing at that given time. In this case, the fundamental elements sound acceptable, and there has been great effort to learn as much as possible about a given modality of building...such as cobb. However, when we get too close to a subject modality, romance for the method often blinds us to better options.

Here is where the "concept" of "bag building" comes under scrutiny. I have been around building of all types long enough to understand that it takes a very long time to really know if a "concept" has "real legs" and can carry the load of efficiency, durability and comfort compared to other building systems. Just as I warn folks about "reinventing wheels" and the ills of many "modern concepts" of architecture like the silly notion that "air tight" houses are a good thing...I too warn that just because something seems "good" or "easy" does not make it so. I have now seen more "uncomfortable" bag structures than I have seen comfortable...especially when compared to more appropriate vernacular systems for a given region and/or biome. I do not think, in the long run, that bags will be the enduring architectural method some suggest, and just do not have the means to compete with more traditional systems in most cases where they are built. I feel "bag architecture" (in most applications...not all) will go the way of the "geodesic dome" movement, which "Bucky" himself finally acknowledge was strewn with issues and drawbacks in the long run.

Without knowing the finer details, location, actual skill sets and tools available, it is hard to really make a complete evaluation and sound advice there of. It sounds like there is a rough plan, and if more work is required to achieve it over other methods that is acceptable. I only warn against such notions as frugality and efficiency of employed means, methods and materials was a path of wisdom our ancestors seemed to follow when building their architecture which they seemed to do much better than we do today...

Regards,

j

Sam Runner wrote:

I understand that it is a very labor intensive process and I am prepared for that. I am planning on using hyper adobe with the Raschel bags that one can order from bagsupplies.CA
I would like to make an earthbag dome in the style that you don't have to angle them inwards to make a perfect half circle dome, but rather the pointy type.
My intent on building this dome is to cover it with earth, maybe 3 ft thick at the thinnest point.
A question have is if it is possible at all to make a dome, 26' feet in diameter? I thought that you could only do that with a bag that when filled is 266" wide after being tamped? Also, how much do I have to corbel over the edge of the bottom layer to make the shape of the dome I am looking for?

Sam,
I built a 25' dome. I wouldn't recommend anything that size to anyone but an experienced earthbagger. Possible, doable and solid yes, but unnecessarily difficult. 20' is recommended max diameter. 50lb bags are typically used in this construction. 100lb bags (rice weight, not earthen weight) would still not get you 26" tamped. Even still, the larger bags are twice the amount of work...
Nonetheless, I'd build a 26' for someone if contracted, using bomber soil content, but I would not bury something that large, and I would not do it in your climate