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Is earthbag or cob cheaper?  RSS feed

 
Felicia Daniels
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It would just be for my mother, myself, 1 dachshund & 3 cats. We're leaning towards 300 square feet. Is this too big since we want to live tiny to reduce/eliminate utility bills? How much would solar cost for this amount of sq ft? We just want to make sure we have enough room for the 6 of us. We have access to doors, windows, appliances, etc & my grandfather (her dad) can handle the electric & plumbing. We've been reading about both techniques but we'd like to know which one is cheaper & the quickest? If earthbag is we have access to bags from a brewery that gives 50# bags away for free as well as the the bags our dog & cat food comes in. And for earthbags what's the cheapest & best exterior & interior plaster? We haven't tested our soil yet to see if it's good enough for cob but in case it isn't good enough what type of soil should we buy & how much would we need for a 300 sq ft house? Same with sand-what type/how much? We can get straw at our local co-op. Or is there a formula to figure this stuff up in case we downsize or expand? Given what I mentioned above about having access to, what all else would we need to get for either method & how much would it cost to build a 300 sq ft house? Thanks guys!! Also we live in Alabama where it's hot & humid about 9 months out of the year (temps above 90 & major humidity) & then for about 3 months it's either nice or really cold & windy. I looked up Alabama's annual rainfall & it's about 57 inches a year. We can sometimes get pretty strong storms & heavy rains.
 
R Scott
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It is the usual permie answer: IT DEPENDS!

Biggest expense will probably be foundation and roof--but they will be about the same for either. Solar and utilities will about be the same, too--lights are lights.

If you have soil onsite that works for either (and water!), the biggest cost difference is usually the bags and wire. It should only take one roll of wire for that small of a house, so that is $50 and the bags are free.

Earthbag is definitely EASIER. Which means FASTER. Which means CHEAPER if you are paying to live somewhere else now. Or need help. Cob is HARD WORK!!!
 
Felicia Daniels
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R Scott wrote:It is the usual permie answer: IT DEPENDS!

Biggest expense will probably be foundation and roof--but they will be about the same for either. Solar and utilities will about be the same, too--lights are lights.

If you have soil onsite that works for either (and water!), the biggest cost difference is usually the bags and wire. It should only take one roll of wire for that small of a house, so that is $50 and the bags are free.

Earthbag is definitely EASIER. Which means FASTER. Which means CHEAPER if you are paying to live somewhere else now. Or need help. Cob is HARD WORK!!!


We're thinking about going with led lights. Would this be cheaper? We're also going to use an alcohol stove & oven. We're trying to think of other appliances (we may use our own for now until we have extra $ for these different types of appliances) that require no electricity. Are there fridges & freezers that don't need electricity? And how do compost toilets work? Are they worth it?

We own our own land & have for 11 years which has city water. We're trying to figure out how to rain harvest safely so that we don't get sick & can use it for laundry, baths, etc. Is the foundation the same for ebag & cob? What would we have to buy for the foundation? And I love the idea of a reciprocal roof. Can this kind of roof be used with either method? We've got dozens of pine trees that stretch for about 1/2 an acre. Could we cut these down to use for the roof & for any lumber we may need or would it take a long time to let them air out & be treated?
 
R Scott
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Earthbag and Cob both need fairly similar foundation specs for a given site--both are HEAVY massive walls, but what that takes vary a lot based on the site soils and conditions. You are southern, so frost protection is minimal. If you can do a rubble trench, the are both really affordable--$50 for a big roll of drain tile, an hour of mini excavator to dig the trench (or a couple weeks of manual labor), and a dumptruck load of rubble rock.

This is a good source for earthbag building info: http://www.naturalbuildingblog.com/

 
Kevin EarthSoul
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If you're going cheap, you may even find a source of free "urbanite" for your rubble trench. (Urbanite is code for "broken pieces of concrete produced by demolition")

However, based on the questions you're asking, it sounds to me like you have a lot more homework to do. It's worth it to invest in a couple of good books on earthen construction.

Here are a couple of books I have seen recommended previously:
Cob building: http://amzn.com/1890132349
Earthbag building: http://amzn.com/0865715076

I have the second book, and have read it, and it's highly detailed, although more tuned to a dry, desert climate. I have no personal experience in building an earthen home, but I have done a LOT of homework on the subject.

One thing that's easy to get sucked into as a beginner is overly focusing on the walls. Raising walls is probably the simplest part of earthen construction. It likely gets so much focus, because it's the part that is most likely to be done by the homeowner. But if you want a building that will be safe and will last a while, you need to pay at least equal attention to your foundation and stem-walls, as well as your bond-beam and roof (unless you're going to do a dome, which has separate challenges). Improper foundations can cause your walls to fail due to shifting or moisture wicking. Improper roofs can leak or break when the winds blow.

You mentioned your interest in harvesting rainwater for household use. That requires a potable roofing material over at least a part of the roof, and some decent filtration systems. You can reuse the same water several times, if you plan well.

You can relieve yourself of some issues if you consider going with a post and beam style of construction, with earthbag or cob in-fill. However, if you do that, you might change strategies to go with a straw-bale or light-clay in-fill, as those are more insulating. You already mentioned having a source of straw locally. Also, in the South, you have access to cheap insulation in the form of rice-hulls. In a warm, humid climate like the South, insulated walls are a better option than high-mass. You can help keep things cool by building a bit under grade, but beware of your water-table. Given the rainfall you get, you'll want nice, deep eaves. I would consider doing a home with a roof that comes down over a wrap-around porch. That can be screened in against bugs, and be a nice, shady place to stay cool, as well as keeping the sun off the walls. That type of model would really support a post-and-beam style, since you'll want to support the roof with posts on the outer perimeter of the porch. You could even build the roof first, and then raise walls underneath it, creating a shady, dry area to do all that labor.



 
Felicia Daniels
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Kevin EarthSoul wrote:If you're going cheap, you may even find a source of free "urbanite" for your rubble trench. (Urbanite is code for "broken pieces of concrete produced by demolition")

However, based on the questions you're asking, it sounds to me like you have a lot more homework to do. It's worth it to invest in a couple of good books on earthen construction.

Here are a couple of books I have seen recommended previously:
Cob building: http://amzn.com/1890132349
Earthbag building: http://amzn.com/0865715076

I have the second book, and have read it, and it's highly detailed, although more tuned to a dry, desert climate. I have no personal experience in building an earthen home, but I have done a LOT of homework on the subject.

One thing that's easy to get sucked into as a beginner is overly focusing on the walls. Raising walls is probably the simplest part of earthen construction. It likely gets so much focus, because it's the part that is most likely to be done by the homeowner. But if you want a building that will be safe and will last a while, you need to pay at least equal attention to your foundation and stem-walls, as well as your bond-beam and roof (unless you're going to do a dome, which has separate challenges). Improper foundations can cause your walls to fail due to shifting or moisture wicking. Improper roofs can leak or break when the winds blow.

You mentioned your interest in harvesting rainwater for household use. That requires a potable roofing material over at least a part of the roof, and some decent filtration systems. You can reuse the same water several times, if you plan well.

You can relieve yourself of some issues if you consider going with a post and beam style of construction, with earthbag or cob in-fill. However, if you do that, you might change strategies to go with a straw-bale or light-clay in-fill, as those are more insulating. You already mentioned having a source of straw locally. Also, in the South, you have access to cheap insulation in the form of rice-hulls. In a warm, humid climate like the South, insulated walls are a better option than high-mass. You can help keep things cool by building a bit under grade, but beware of your water-table. Given the rainfall you get, you'll want nice, deep eaves. I would consider doing a home with a roof that comes down over a wrap-around porch. That can be screened in against bugs, and be a nice, shady place to stay cool, as well as keeping the sun off the walls. That type of model would really support a post-and-beam style, since you'll want to support the roof with posts on the outer perimeter of the porch. You could even build the roof first, and then raise walls underneath it, creating a shady, dry area to do all that labor.





Thanks guys!! What about an underground earthbag house? I read something that said an u/g e/b house would be a good fit for our climate. But how would we protect the walls from moisture & leaks? Would the walls be able to breather with being underground? It mentioned using an earthen plaster on the walls but would we need to mix in lime? How would we do the roof with an u/g house? Also, how would we be able to let in light with it being u/g? What type of sand would we need for the plaster? My grandfather might be able to get his hands on an excavator but if not, how much would it cost to rent one per hour? He does have access to a dump truck though. Should we just use the soil we dig up to fill the earth bags? Would that be a good way to go or would we need to buy rice hulls or something similar? How do we figure out how many bags/how much fill we need per sq footage? Thanks!!!
 
Kevin EarthSoul
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Building underground is pretty ambitious. Most people do partial below-grade building. It's not just about light, but ventilation, as well. Also, fully underground means you've dug in really deep, which increases the risk of hitting water-table. It adds a whole new layer of challenges. Most people seem to go with partial backfill. In more northerly climates, backfilling the North side up to the top of the wall, while leaving the Southern side open, with glazing for passive solar gain is very common. But in your climate, you're mostly about trying to stay cool and dry, which recommends against digging in too deep, unless you want to try to fully moisture-proof your floors and walls.

I would focus on: insulation, shading (not just with a deep roof, but also good shade trees), and keeping a cool floor. Backfilling up to a few feet might be good, but you'll be better off making a home that will ventilate well during Summer. I would consider building a stone fixture that can act as a ventilated heat-sink, with a high ceiling that can allow warm air to rise and then vent out. Plenty of air-moving ceiling fans.

One good clue is to look at the vernacular building in the area. In the South, porch-space was used extensively, and doors and windows were placed to enhance cross-ventilation through the house. On a 100 degree August day with 90+% humidity, there will be no way to get a house cooled without A/C, however. I would consider a geo-thermal heat-pump as the most efficient means of cooling. It would also provide the heating you needed for the short Winter.

Also, consider a "living roof". With the small home you're planning, you aren't spanning great distances, so the weight of a living roof could be borne. These could help keep your home much cooler. I could just imagine a living roof with wisteria hanging down off the eaves, further shading a lovely porch. If you have plenty of windows in the walls, and sufficient out-ventilation from the peak of the roof, your home should stay comfortable for most of the year.
 
leila hamaya
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earth bags are cheaper and faster, imo. cob is much slower, though also can be extremely cheap. especially as you have a source of free bags though, earth bag is what i would go with...although i am also interested in light clay straw with a post and beam structure.

i am in favor of starting it out and then figuring it out as you go along, though i know many people dont work well with this method. i tell myself things like...i only need to know the next couple of steps and then when thats done i will see whats next. i dont know that i would recommend it, but its how i get to thinking about things. a vague plan, some measurements, some drawing, and then get into it and figure it out as i go.
also i have some experience, so i t helps to feel like i can pull it off eventually if i just get in there and step by step do it.... before i figure it all out. doing a lot of drawings and thinking on paper helps me.

heres a link to a mega source for free books and information on earth building, for some more reading

http://jubilee101.com/subscription/free-earthbag-construction-books/

http://jubilee101.com/subscription/free-cob-construction-books/

http://jubilee101.com/

havent gotten through most of this one site, but theres some good information and how to books available there.
 
R Scott
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Kevin EarthSoul wrote:One good clue is to look at the vernacular building in the area. In the South, porch-space was used extensively, and doors and windows were placed to enhance cross-ventilation through the house. On a 100 degree August day with 90+% humidity, there will be no way to get a house cooled without A/C, however. I would consider a geo-thermal heat-pump as the most efficient means of cooling. It would also provide the heating you needed for the short Winter.


TREES!! All homes had deciduous trees surrounding them. That can give you a 15-20 degree microclimate boost. Build within an existing stand of trees if at all possible.

For 300sf, a small (CHEAP) window AC unit will get the job done for only a little power, if the trees are not enough. But still more than your budget allows if you are going solar.
 
Kevin EarthSoul
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R Scott wrote:
Kevin EarthSoul wrote:One good clue is to look at the vernacular building in the area. In the South, porch-space was used extensively, and doors and windows were placed to enhance cross-ventilation through the house. On a 100 degree August day with 90+% humidity, there will be no way to get a house cooled without A/C, however. I would consider a geo-thermal heat-pump as the most efficient means of cooling. It would also provide the heating you needed for the short Winter.


TREES!! All homes had deciduous trees surrounding them. That can give you a 15-20 degree microclimate boost. Build within an existing stand of trees if at all possible.

For 300sf, a small (CHEAP) window AC unit will get the job done for only a little power, if the trees are not enough. But still more than your budget allows if you are going solar.


LOL I could have sworn I mentioned trees as a part of "shade", but I think I got distracted and left that out. YES. Glad you mentioned that. It's also a part of the vernacular architecture there to build under the towering sycamores and chestnuts.
 
Felicia Daniels
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Kevin EarthSoul wrote:Building underground is pretty ambitious. Most people do partial below-grade building. It's not just about light, but ventilation, as well. Also, fully underground means you've dug in really deep, which increases the risk of hitting water-table. It adds a whole new layer of challenges. Most people seem to go with partial backfill. In more northerly climates, backfilling the North side up to the top of the wall, while leaving the Southern side open, with glazing for passive solar gain is very common. But in your climate, you're mostly about trying to stay cool and dry, which recommends against digging in too deep, unless you want to try to fully moisture-proof your floors and walls.

I would focus on: insulation, shading (not just with a deep roof, but also good shade trees), and keeping a cool floor. Backfilling up to a few feet might be good, but you'll be better off making a home that will ventilate well during Summer. I would consider building a stone fixture that can act as a ventilated heat-sink, with a high ceiling that can allow warm air to rise and then vent out. Plenty of air-moving ceiling fans.

One good clue is to look at the vernacular building in the area. In the South, porch-space was used extensively, and doors and windows were placed to enhance cross-ventilation through the house. On a 100 degree August day with 90+% humidity, there will be no way to get a house cooled without A/C, however. I would consider a geo-thermal heat-pump as the most efficient means of cooling. It would also provide the heating you needed for the short Winter.

Also, consider a "living roof". With the small home you're planning, you aren't spanning great distances, so the weight of a living roof could be borne. These could help keep your home much cooler. I could just imagine a living roof with wisteria hanging down off the eaves, further shading a lovely porch. If you have plenty of windows in the walls, and sufficient out-ventilation from the peak of the roof, your home should stay comfortable for most of the year.


Definitely don't want to make things more complicated than needed. Should we do a wrap around porch or would that block too much sun? How deep do you think would the most we should dig down? Should we just use the soil we dig up or do you recommend a certain kind of fill? What would be the best plaster for us and how would we make it? How much fill & plaster would we need? And how many 50# bags? This may be stupid but what do you mean by a stone fixture as a ventilated heat sink? Does that mean stone rocks as the foundation and wrapped all the way around & up however high before adding the ebags? We were thinking about an 8' high ceiling or would that be too high? Too low? How do we do a living roof? And how can we use the trees? What steps would we take to use them? I looked up geo thermal heat pumps on amazon & they were all over $2000 and that's just more than we have right now. We've only got a budget of about $2600 to build the house & including any fixtures we don't have in the trailer we can swap over. Would a round house be best? How do you do the doors & windows, etc in a round house? I have attached a couple of pictures: 2 of the area we're wanting to build it in & 1 of a floor plan we want it to be or resemble. We'd like a loft but unsure what kind of challenge or cost that would bring us? The yard pictures were taken a little after 6 pm. This yard area has direct sun for about 5 to 7 hours a day.
yard.jpg
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yard2.jpg
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2-earthbag-tiny-house-plans-spiral.jpg
[Thumbnail for 2-earthbag-tiny-house-plans-spiral.jpg]
 
Felicia Daniels
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Also we like the idea of a house that looks like this or do you think this would work where we live?
earthbag-homes-7.jpg
[Thumbnail for earthbag-homes-7.jpg]
earthbag-homes-4.jpg
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earthbag-homes-1.jpg
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John Elliott
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This is a good place for me to give Earthship another plug. Here is the first of their videos of what they have done in Haiti (hot and rainy like an AL summer):



The next time you are out taking pictures, take a shovel and show us what the dirt is like. I'm will wager you have to dig less than 12" before you hit solid clay, which would mean you have all the cob you would want or need right under your feet.
 
Felicia Daniels
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John Elliott wrote:This is a good place for me to give Earthship another plug. Here is the first of their videos of what they have done in Haiti (hot and rainy like an AL summer):



The next time you are out taking pictures, take a shovel and show us what the dirt is like. I'm will wager you have to dig less than 12" before you hit solid clay, which would mean you have all the cob you would want or need right under your feet.


I have attached a picture of some dirt that we dug up when we built out chicken pen. If you zoom in you can see the pile of dirt next to the digger that came out of the hole. What do you think? Clay maybe?
BeFunkycoop.jpg.jpg
[Thumbnail for BeFunkycoop.jpg.jpg]
 
John Elliott
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Looks promising. If it balls up when it is wet and you can play with it in your hands like silly putty or a stiff bread dough, then yes, it has enough clay to be considered possible building material.

 
Felicia Daniels
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I'll try that today and see how it does. I hope it works! If it does, what type of sand do we need to buy to go along with it for the plaster? Would all purpose work? And if it doesn't work, what type of clay do we need to buy? How do we figure out how much of everything to buy?
 
Kat Green
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I don't know if this idea would be usable but take a look at this cement/cow (or goat) constructed house.
http://atlasobscura.kinja.com/a-minimalist-house-made-with-cement-hay-and-a-baby-co-1564449114
 
I agree. Here's the link: http://richsoil.com/email
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