My partner and I are looking to buy land in TN and build houses and a permaculture garden.
I always wanted an earthbag house, but he doesn't like the idea of using plastic and barbed-wire. I liked earthbag because you don't have to worry about a timber based roof.  We don't like strawbale because its square, but I like it because it seems quicker. He wants cob because its beautiful, free-form, and he's reading the hand sculpted house. I think cob seems great too, but I'd like something quick and pretty to live in while we build a dream house after that. My friends that built a cob greenhouse have cracking problems and the condensation from a large window is starting to deteriorate the cob.
I hear the reasons for cracking are not enough sand or not enough straw; measurements that one could make sure they got right. But I'm still scared of spending time on a house that might fall apart.
The idea of blending cob and straw bale (cobbale) intrigues me but I'm not sure I fully know the reason for using it. Except, for a first small house, it would be quicker and we could learn about both mediums. Can cob-bale be circular?
Thanks for your incite! I'll keep reading up on it.

oh, and also: one piece of land that we're looking at is technically in a flood plain. It flooded once in the past 100 years...not too many inches i dont think...
I've read that earthbag is great at taking flooding and drying out and being ok.
maybe we could have an earthbag base? hmmm...

You'll have to work out which building medium you want to use between the two of you (although I would suggest, if you are going to have a temporary house while building the permanent one, to put up the temporary place with the materials and method you plan to use on the permanent one so you get some practice in).  What I want to comment on is that flood plain -- before you even consider buying flood plain to build on, check with the local building department and make SURE that they will let you build there!  In a lot of places it's a total no-go.

Kathleen

dream home = cost of materials + [difficulty x time to complete project]

I just made that up.       Straw bale can be round.    I say build a cute small pod, learn from it, live in it, and build the next one and then when thats done you will already have a guest house.

I know where I live you cant even build in a 500 yr flood plain.  Do your checking just like the other post says.  There are ways around it if you want to build up the land but that will come with extra cost. 

From my experience with cob, assuming you have the mix about right, the cracking wont be as bad if you cob as early in spring as possible.  This gives the cob a longer dry out time and prevents it from being to dry on outside while still damp inside.  Summer is the worst time to cob in my opinion, but can and has been done and is allot of fun.

On round construction...its very doable.  Cob or straw bale, or mix the too. Bales bend, they are only rectangle because we make them that way.  Who says we cant bend them and trim them.

Condensation can be a problem like any other material.  I whence every time I see a cob building go up with single pane glass.  I suggest a good window buck frame (wood etc) at least with single pane.  Also the finish on walls around these areas could be more water resistant.  Some form of lime sand mix and maybe a sealer where water condensation would accumulate. The tops of the walls tend to get frosty too if not done right.  The temp is higher at the ceiling level in the cold period than the rest of the wall and causes condensation.  I have seen this part of the upper wall (1-2ft) constructed of a more insulating mix of cob, (heavy on the straw).  It also seems that as people build, the wall seems to be thinner here.  At ilovecob.com  there is a photo somewhere in the gallery that shows adding bags of straw in this area and cobbing them in.  Also show the problem with condensation. 

I love cob and straw bale and there is no reason we all should not do it.  Just read read and read some more and learn from all of our mistakes and have fun.  You build it, you can fix it.

get the mix right for the cob and you wont have cracks. the book has several testing methods to help you get the mix correct. small cracks are not a problem at all.  if you are looking at bale give Ianto a call and ask about cobbale (its  in a thumbnail; 8 inches of cob on the inside walls. bales stabilized with cob and a good thick plaster on the outside.

in my experience the cobbale is about the best way to build i have ever seen. the bale goes up fast giving you a shelter and the cob can be done in comfort. as Ianto's apprentice for two years i fell in love with cobbale for several other reasons but the ones above are what makes most folks happy.

dont buy the flood plane, that bottom land is best for growing food not building houses on. the fella in budda texas is a lesson learned when he bought and built in the 100 year flood plane and had his cob house (still standing as far as i know) stuff  destroyed soon after completion.

Flood plain ....  wow - that seems the key to me. 

What is the soil like under that?  How cold does it get there?

Thanks for everyones input!
We are going back to the property in a couple weeks and I plan on asking the neighbors what the recent flood was like, and maybe some other questions about the locale. I'm hoping we find a different piece of property that catches our eye. Everything I've read says do not risk building on a flood plain.
There are no building restrictions.
...
What do you cut straw bales with to make them round?
Could I make my own double pane windows using two glass table tops?

ardillaDeneys wrote:
What do you cut straw bales with to make them round?
Could I make my own double pane windows using two glass table tops?

For the straw bale, depending on how gradual the external wall is you use a bale mallet to change the shape from rectangular to trapezoidal for large diameter walls or you stuff the spaces at the edges with loose straw packed in.

Yes you can make your own double paned windows.  You will want a thermal break in the frame between the panes to reduce thermal bridging as much as possible.

If there truly are no building restrictions in your flood plain property (the EPA may have jurisdiction even if local building authorities don't care, so check -- anonymously!), then the best way to build there would be on pilings so when the area DOES flood again (and it will!), the water will go under your house, rather than through it! 

Where my family is from, a little valley in the Oregon Coast Range, floods are yearly events, and the house my mother was born in was frequently flooded.  Even once in a lifetime would be too much.

Kathleen

what valley Kathleen?

I am from Coquille

There are many wonderful links, books, and sites on all sorts of alternative combined building materials.  As far as I have seen there isn't any reason not to combine any styles and materials except for your environment and availability.  Cob, cord, rammed earth, straw bale,  bottles, cans etc.

On moisture there is some very interesting research into magnesium Oxide (MGO) as an incredible moisture control.  It is was the morter used in the great wall of China.  Rather pricey but worth a look www.substanceproducts.com is one source.

Flood Plane NO WAY!  Be prepared for LOTS of earth moving, and there are considerations even if you do build up the soil in an area, it needs to be compacted, preferably over time.  I do NOT live in a 100 year flood plane, although it is close to sea level.  In the hurricane shadow so even though I'm in the very deepest south they are rare, 45+ years apart.  That said the only one to hit here in 45 years put 1/2 my property under water by as much as 3 feet in some places.  Fortunately the structures were on the high part but my DD and Husband had just built a studio with an 18" above ground wall, the water was within an inch of the top of it.  See if you can get a topographical map of the place, look at areal views via google earth, look for indications of the low and high spots etc.  Also take a careful look at the water table level.  It may be high enough that you find yourself with sink holes after a good rain.  (My tractor once ran out of fuel over an area that seemed perfectly solid but within an hour it was sinking into what quickly became a pond) 
Building on Pilings could work but how high is high enough and I don't see that as working well with heavy earthen construction or bales.  Also septic, compost toilet, and even grey water will all be affected by the water table.

Hope something here is helpful.

Here in Albuquerque our adobe homes have outlasted floods. It's been a while since a big one (1940's) but the valley and old town have withstood flooding and many of the buildings are several hundred years old and no worse for wear. Curves are easy with adobe and the smaller row height makes windows and door placement flexible. They aren't prone to swelling or cracking. The material has good R-value and less square footage used for walls compared to alternatives. If you don't have a supplier, making adobes is relatively easy (and if you have materials for cob, you have it for adobe).

drying conditions differences between NM and TN are rather profound. 

Ernie wrote:
drying conditions differences between NM and TN are rather profound. 

LOL - Quite true and my experience is definitely NM based. Though to me, having less biological material in the mix seems like an advantage in a humid area when it comes to flooding. One would definitely need to consider timing for initial block curing but that would probably be the case for cob and SB.

I was thinking about the adobi drying time compared to the monolithic cob. you might get away with the bricks drying fast in the summer. either method will take about the same amount of time adobi in brick making and cob in the building of it its self. both will and have withstood flooding. its the possessions that usually dont do so well.

thanks for bringing this up by the by
makes me think about all this. sometimes folks forget the biggest loss in a disaster is not the structure (natural building does connect us a bit tighter to our houses) its the stuff in the structure that is devastating.  papers and refrigerator art, aunt Mabels silver set. that tapestry you spent two years making are the things that are the real loss. the other stuff is just stuff TV's and whatnot.

Well, I think I agree with the bit about "don't buy stuff in the flood plain."  If you haven't bought yet, focus on land that is on a slope.

From what I've heard, cob is anything but quick. In the southeast where we live, the relative humidity may be too high to pull off straw bale (because of potential mold issues), unless perhaps you really make it water resistant as outlined in "Building Green" - they put tyvek wrap around the bottom bale and a high stemwall would be definitely recommended. My better half and I build an earthbag home and I think it's one of the best bets for our area. A thread discussing the ins and outs: http://www.permies.com/permaculture-forums/3277_0/alternative-building/dirt-bag-structures - read it!

On our website (www.asustainablelife.info), we have pictures of the earthbag cabin that we built. The walls went up quick (4 months or so w/ mostly only 2 people working). The bags also provide mechanical support that cob lacks - there's a story in "Earthbag Building" about their earthbag "honey house" flooding and it only making the bags stronger. Still - you probably don't want to build in a flood plane (just my thought on the matter).

Some insulation on the outside would also be helpful. Putting the bags sideways and putting some recycled styrofoam at the ends would give you alot of thermal mass w/ 2' thick walls and the insulation would help keep you warm (or at least ambient earth temperature) in the winter. Our walls are 1' thick and it was a challenge keeping our place warm through the cold, dark winter. We're thinking of making a perlite or vermiculite plaster to help insulate the outside, at least on the colder northern side that doesn't get any sunlight in the winter months. Also, without insulation, condensation becomes an issue and we've had some issues with it. When the walls are cold and meet the hot, moist inside air, condensation takes place and has lead to some mold growth on our lime painted walls. A coat of vinegar mixed with baking soda seems to have put a stop to it (we think it can't grow on the salt).

The optimal property would be on a gradual, south facing slope. An earth house that doesn't get lots of sun would probably be a cold, cold (did I mention cold?) place. Also you can install some big double or triple paned windows to get lots of solar gain. Thick, insulated curtains would be good for when there is too much or too little sun.

Ernie wrote:
what valley Kathleen?

I am from Coquille

Sorry I didn't see this sooner, Ernie!  I've been busy and haven't been posting much here for a while.  My family homesteaded in the 1870's near Florence, up the North Fork of the Siuslaw River.  I love it there.  But land is so expensive there now that it's way out of my reach.  (One good thing about this Depression we are in now -- I hope that land prices will eventually drop enough that I'll be able to buy a place of my own, though I'm not too optimistic about it being on the North Fork!)

Kathleen

Look at poured earth.

http://www.michaelfrerking.com/index.php
http://www.ehow.com/how_2140534_build-house-from-poured-earth.html
http://www.greenhomebuilding.com/poured_earth.htm

Use clay from your land, flyash (recycling an industrial waste product) and some cement.  Poured earth can be the above-ground part of a partially-underground house.  Make ONE form - square, rectangular, round, oval, spiral, and use it over and over to add rooms, right away or in the future.  Our design uses a golden mean spiral wooden form

http://www.soulsofdistortion.nl/images/picture%2025.gif
http://www.floweroflife.org/spiral01.htm

designed by Michael Frerking that can be poured, then flipped to pour a spiral in the opposite direction, then flipped two more times to make four spirals that surround a small square center for the kitchen.  Building the square involves one more small straight wall form that is used four times for the four connecting walls.  Walls are 24 to 36 inches thick, depending on whether you want it to last 500 years or 1000 years.

As advised above, build the form, pour one room (one of ours is 900 square feet), live in it and learn from it, then pour another room if needed (eg, growing kids) as time and funds become available.  The expression is "dirt cheap" for a reason!