No, don't even try. Any system out there that "seals" will inevitably fail and/or harm the masonry matrix.
I was thinking I could perhaps fix that problem by applying a moisture barrier on the *outside* of the concrete (leaving the inside, and the cob layer, natural, so that it doesn't have buildup problems). Do you think that would work?
Romanticizing a building medium is not always in one's best interest. Determination is a good thing, but don't try to make something work when something else maybe better, easier, and perhaps more applicable.
I'm not seeing any other option for having a cob house underground. If the cob touched the dirt, it would just slowly break down from rain soaking. I am determined to have cob as the inside layer of the walls plus any interior walls.
Dry laid stone on gravel trench footings, (this could be lime mortared and/or render in some cases if the need, desire, and aesthetic follows your ideal, and skill sets. This is the outer retaining wall matrix that then has a "thermal air break" between it and the "below grade" architecture. This "thermal air break" should be a minimum of 100mm (~4") but I recommend 1 to several meters (~3' or greater). This style of subterranean building method elements the need for "sealing walls" from moisture and rising damp, and provides a maintenance access space around the primary living environment that can have several functions, including but not limited to "root cellar" style storage. You will still have to deal with the heavy timber roof, which also should have "cold roof" venting principles employed within it, especially in colder or humid climates. These roof systems, (most of which are "living roofs") are a minimum of 1 meter thick up to 5 or more meters. One of the reasons for the heavy timber and advance building skill sets.
If the concrete plus sealer won't work for the layer between the cob and the earth, could you recommend something that would?
I've seen lots and lots of examples of underground houses that work just fine.
What are the modern ones doing to seal from moisture, and why won't that work in this case?
-Steel beaming (load bearing in walls and roof) (my other half does welding) for support (3+ feet of earth overhead, so we feel we need the extra safeguard)
-On the outside part of the walls underground, and the floor - concrete and local rock, moisture sealed.
-Inside half of the walls, plus any indoor walls - cob
No, and mainly because of the OPC, other than perhaps in a desert environment, but then I would still rely on natural materials and not something like OPC with it's very large carbon footprint.
-*Front wall (single side uncovered by earth mounding) - 2-3ft stone base (with nice dyed concrete between), then inner core concrete/stone moisture sealed and both outside and indoor layers cob, with deep overhang. Will this work?
We are thinking that the moisture sealed concrete protecting the cob from the earth will stop (or greatly reduce) the moisture issues, while still letting the cob breath. We considered doing it all out of mortar and local stone, but we love the fluid, rounded look of cob.
If their inner walls are dry, I should be able to use cob inside.
When the "lemmings are running for their hole in the ground from a predator...that is a good thing. When the little fellows are running for the edge of a cliff...not so good. Just because there is a larger cultural movement to build a certain way from the FAD and FASHION of it, does not mean it is a good idea, or being done in a proper and enduring way. Let talk to folks that have lived in one for 20 years or more, ask what they like and don't like, and whether they would do it again. Many I have spoken with, would not, and those that do, have a real good understanding of design and construction principles, as well as, a solid understanding of "dugin" vernacular architecture.
I know a lot of cob structures are being build in Oregon, so they must deal with the humidity somehow.
To achieve the positive aspects of "earthship," "wofati" or "dugin" building methods, and the "thermal inertia" they can provide, you will require a minimum of 1.5 to 2 meters of earth (~ 5' +); 300mm (1') is not nearly enough, and will only act as a heat sink pulling you heat from the structure.
So, all in all, it's come to less of an underground structure and more of a sod-roof house (1ft or so of earth) with partial burming (?berming?)...
Sahara Sjovaettir wrote:Our plans are to build an earth-sheltered cob house, eventually, in Oregon.