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How much does it cost to build a cob house? What do I need? I'm lost  RSS feed

 
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My mother & I want to build a small cob house (500 sq ft) and I'm trying to work out an estimate but I'm having trouble figuring out how much we need of everything. I found a brewery that will give us all the 50 lb polypropylene rice bags we want so that cuts away that big expense. I've contacted a sand & gravel company about rough fill dirt & I'm waiting to hear back from them. On their site it says that the rough fill soil is usually offered free with the only cost being gas for the truck to deliver it but I only live about 15 minutes away from them so I'm thinking that won't be a big expense & if it will be my grandfather can get his hands on a dump truck to deliver it to us. Here's the other materials I've come across that we would need: (correct me if I'm wrong or if there's something I haven't thought to add)
*4 point barbed wire (I'm thinking just one 1320 foot roll w/ 2 strands layered between each row of bags. does this sound right for 500 sq ft? The house will be a 20Wx25Lx7H)
*lumber for the doors & windows but with only a few doors & windows I don't think this will be a big expense
*a tamper
*wheel barrow/shovels/wire cutter/level/hammers (all of these we have so no expense here)
*4 gallon buckets with the bottoms cut off to use as shutes for the bags & spare 4 gallon buckets to hold the right amount of rough fill so we get the same amount in each bag
*mason line & stakes
*a hoe (is there a certain kind that works best with digging the trench?)
*cement mixer (found a portable one on Home Depot's site for $285)

The cob plaster is what I'm having the hardest time estimating for. I read that all we have to use is clay, sand, water & straw. I think it was 2 buckets of clay, 1 of sand, 1 of water & a handful of chopped straw. Is it ok to use the rough fill soil as the clay? And for the sand can we use Quikrete All Purpose Sand? If not, what's the cheapest sand we can use? And how much rough fill would we need for the bags & the plaster? And how much sand for the cob? We want to use cob plaster on the outside & inside. And we'd like to paint the plaster so does anyone know what kind of paint we can use on cob?

Also, we'd like to keep the building cost below $3000. Is this possible? Thanks & sorry for all the questions. Any & all tips/advice is greatly appreciated!! Oh and a basic layout would be a living room, kitchen, small eating nook, 1 bedroom, 1 bathroom (preferably 2 if possible) and a loft. How do you add a loft inside of one of these houses? And before I forget, we're thinking about just using our existing power & just having it hooked up to the cob house. Or would we save money in the long run by going solar? How do you do that & how much would it cost for the size of our house?

Thanks!!!
 
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Welcome Felicia to Permies!

Sorry we haven't gotten to you before now, yet your opener is kinda of a nebulous question/statement. It is really hard (impossible) to answer that question even generically without know many different facets. Especially for an owner builder with limited or no skill sets in architecture design and building practices...let alone a challenging project the size you are attempting. I facilitate and teach natural building and still don't condone "structural cobb" for the beginner (and even most I see that are experienced.)

Do you know the man hours it will take to dig and/or mix you cobb?

Have you calculated the volume of material you will need?

Do you know your local clays well that will form the cobb?

Will the project require permitting?

The questions just go on from here...

Sorry if this is a downer...

j
 
Mother Tree
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This house was built for £150, according to this article.

 
gardener
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Jay and Burra --- Did you read her post completely ? It's not about cob.
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Felicia --- You have described the building of an earth bag house with a cob plaster. You would be well advised to spend many hours looking around YouTube and other sites concerned with cob. Search cob building, cob mixing, cob mixtures, cob workshop... Then do the same for earth bag building. You'll see that they are very different. Cob requires less purchased materials than almost any other building system, with more labor. Attend a workshop for whichever method you choose.

You mentioned making an earthen plaster with the stuff that fills earth bags. This won't work unless by rare chance the dirt beneath your feet happens to be a mixture of good binding clay mixed with sand. Earth bags can be filled with just about anything that won't rot.
 
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Felicia Daniels wrote:
Also, we'd like to keep the building cost below $3000. Is this possible?



The walls will be just a small fraction of the cost of the house.

You'll spend most of your money on:

Foundation
Doors and windows
Wiring and light fixtures
Heating
Plumbing and plumbing fixtures
Cabinets and counters
Insulation
Roof framing and roof covering

(And that's if you use earth for the floorcovering and wallcovering.)

In fact, my Scientific Wild Arse Guess would be that the walls might be 10% of your total cost, and the other parts 90%. So, if you can get the walls done at $300, and everything else at $2,700, then you can hit your $3,000 budget target.


That's going to require some executive-level scrounging.
Quick two-question quiz:
1. What's the most expensive thing you've ever scrounged?
2. How many different places have you scrounged building materials from in the last 30 days?
 
Dale Hodgins
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I can answer that ! The most expensive thing I've ever scrounged was a really high quality house with stained glass windows and lots of quality wood work. Everything to build another story was also scrounged or paid for with the proceeds of scruonging. It sold for $293,000.

I grabbed stuff from 3 locations last month.

I often let customers pay for materials with sweat equity.

Most cob buildings that I've seen use lots of found items. The walls don't cost much in materials.

I could produce a livable 300 sq. ft. structure for $1500 plus a ton of work.

This cottage contains about $1500 of store bought items. All wood, windows and doors are reused.
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Mike Cantrell
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Dale Hodgins wrote:I can answer that ! The most expensive thing I've ever scrounged was a really high quality house with stained glass windows and lots of quality wood work. Everything to build another story was also scrounged or paid for with the proceeds of scruonging. It sold for $293,000.


Ha!
Dale, I meant that for the OP Felicia. You're exactly who I had in mind when I said she's going to need to perform some executive-level scrounging. But what I was trying to do was express to her what it will take to get a home built under $3k. It'll take extensive, diligent, creative scrounging. Because nobody puts "Complete 300 SF House Kit, Just Add Walls" on Freecycle. You've gotta have practice and connections (connections as basic as the employees of some store who recognize and don't mind you picking through their junk, that's still connections).

Has she practiced this? Does she have some of these connections? We don't know yet. Hopefully she'll tell us.
 
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There is so much to know and so much to learn. Indeed, our OP is talking about earth bag building, not cob. Perfectly good way of building, lots of people with good information about it out there on the internet, some pretty good examples on YouTube.

The item that concerns me is e discussion of using "rough fill" brought in by truck. In general, that is material someone paid to have removed from their site. There are many reasons they would want it removed. Some are harmless, but it is entirely possible that you could get a truckload of contaminated material that someone else paid a premium to get removed from their site.

One of the biggest benefits with all of the earthen construction systems is that much of the material you need is right under your feet. You just have to dig it up

I would be very reluctant to build my home out of someone else's rejected soil without knowing exactly why they had it removed.
 
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Sounds like questions I would ask if I were ready to build, Felicia!

The whole personality thing might have a lot to do with it.
Some people are naturally gregarious, know a lot of people, know how to scrounge, make deals, shmooze.

Some are a bit more reserved and might have a hard time finding free stuff without going waaaaay out of their comfort zone.
I think you need to be able to approach people you may not even know and boldly present requests and be be able to work deals.

One way is to join local community facebook pages. There are a lot of friendly helpful people who you can network with. Many may have just what you need, or know someone who does. You may make friends of others who are very curious about what you are about to undertake. I suspect you may get volunteer cob stompers, too. LOL
 
steward
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There are a lot of either free, or cheap materials available.
Good sources are Craig's List and Habitat for Humanity stores.

I often see doors & complete window frames (with possibly 1 broken pane) going for "You haul, it's yours" in the freebie section of Craig's List. Habitat for Humanity also has tons of windows, doors, etc. The down side to using these materials is that you may need to line them up (and have them on site) before you begin your planning - you may have to build around the free materials you have acquired. You may have an assortment of odd sizes.

"Free fill" is a mixed bag. If it has been declared 'contaminated', they cannot deliver it to you - it must be taken to a designated facility that is set up to handle it. Much fill is the results of grading for new construction. Most of the 'free' stuff is crap! If it is from the demolition of an old home, it is likely to have been contaminated with the old lead based paints.

I wish you luck, but I think you will need to look carefully in your area to see what free/bargain materials you can come up with.

Free rice bags from a brewery? You must live near a Budweiser brewery. I don't know anybody else (dumb enough) to make beer out of rice.

 
Felicia Daniels
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Thanks for all the answers!! Sorry I'm just now getting back on here. We currently live in a 16x80 trailer and we can reuse our doors, windows, appliances, etc. So we won't have to buy any of these things. We live in Alabama where it's hot & humid from march to november. I didn't realize I was combining the two methods. Which would be better/cheaper: ebag or cob? Or straw? I'm not sure what our soil is like. I will attach a couple of pictures of our ground after we recently built a chicken pen & see if guys can tell from the pictures. If we have to order, how much would we need for a 500 sq ft house? Or we may do about 300 sq feet. And what type of clay & sand? I have also attached a picture of an example floor plan we've been looking at. Also what is the cheapest way to power, heat & cool a cob house? I've been reading about solar & harvesting rain but it all seems so expensive & considering we'd have to go month to month paying for & building our house it would take about a year alone just to get a solar system like the ones I've been reading about. Should we just stick with our power & water companies & are we right in assuming that with the smaller square footage our bills through the companies should drop drastically? In our trailer we pay about $230 a month in power when it's colder & about $180 when it's hot. Our water bill is about $25-$30 a month.
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Felicia Daniels
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I can't get the floor plan picture to upload right now but I will try again later.
 
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