Is my math wrong?

I feel like I might be screwing up these calculations.

Mind, the stud wall calculations are on the bare wood, not counting insulation or sheathing or moisture barriers or anything else. But would those things be *that* much more expensive?

I got interested in this stuff because it was cool and sustainable, but also because it's supposedly cheap. I only have one shot at building a permanent home with a tiny budget, and if the math works out like this, I'm going to have a hard time justifying it.

Advice? Knowledge? Tips?

Well, I cannot get a start on your figures.
Usually the individual items and the number required of those items are listed.
Then with an actual cost per item the cost can be extended.
I dont know what figures you have?

Is that cost per 16' x 10' for exterior wall surface?

As John says, we can't comment on that chart without more detail. Somebody with relevant experience may be able to give a ballpark figure.

If you have a tiny budget, I would plan for the most minimal house you can reasonably inhabit, with provisions for expanding later as means allow. This would likely include a small amount of lightweight interior partitions; wattle-and-daub would keep the earthen esthetic without the bulk of earthbags where the wall is not needed for structural support. If you have any forested land, you may be able to get much of the structural lumber (for roofs and such) from home. Any wood that needs to resist rot can be black locust if that grows near you - fenceposts are regularly listed on craigslist and the like, and you may be able to get some poles custom cut for less than pressure treated lumber would cost. There are other rot-resistant species that grow in different regions.

Based upon what you have presented, the figures seem very reasonable.  But, as others have indicated, I would really like to see more detail.  How long are the boards?  How many of each type are there?  A drawing would help.

I don't understand your chart.

Could you explain how you got those figures and what they mean?

I asked Mr. Google how much 2 x 4 treated lumber cost, he said:

pressure-treated lumber costs between $15 and $25 per square foot.

I asked him how many square ft would be a 10' x 16' and was told 160 sq ft.

I multiplied 25 x 160 and came up with $4000.00.

I believe the treated and plain lumber items are for stud wall framing (not including sheathing etc., as the OP mentioned).

A quick look at those numbers seems like they are in the ballpark for just the rough framing lumber. The rest of the materials to make finished walls would at least double those numbers. Note that exterior walls are hardly ever made completely from treated lumber, unless they are in extremely humid environments or subject to regular wetting. Only sills and decks generally require this.

I'm sorry I haven't gotten back to this thread yet; it wasn't giving me notifications like I asked it to.

I'm comparing the cost for a 16' x 10' stud walls (framing only) to a wall the same size made of hyperadobe.

The wooden framing is being figured as a 16' x 10' based on 2"x4"x16' treated boards for the top and bottom, and 2"x4"x10' studs on 16" centers.

The hyperadobe numbers are based on these calculations:

• On another site, I saw that a typical 18" x 30" individual earthbag winds up about 24" long after it's filled.


• The same site said an individual bag holds a out 100 lbs


• I've also been told the average course height is 4".


• I've been told that a good mixture is 64% sand, 30% clay, 6% cement. I'm figuring on that, even though the final mix just have different proportions.


• The clay is $30/ton and the sand is around $10-20/ton. The cement is about $5.50/80 lbs.


• The tubing I'm looking at is roughly 30¢/foot.


Given all that, a traditional 24" bag that holds 100 lbs in those proportions would be 30 lbs of clay, 64 lbs of sand, and 6 lbs of concrete. I figured the price/lb from the prices of the tons, worked up the cost for 24", then divided it half to get the price per linear foot for a single course. That came out to about 88¢ per foot.

Given a 4" course over a 10' tall wall, I'd need 3 courses/ft of height, meaning 30 courses. So I figured a section 1' long and 10' high would be around $26.37. Multiplying that by 16 (to compare the length of the stud wall), I came out with $421.92 per 16'x10' section.

Hope that helps. Seems clear as mud when I try to explain it.

Edit - I'm going to have to do a stud wall inside eventually anyhow, because the wife refuses to live in a place where she can't use a normal drill bit to hang pictures, and she hates the look of the interiors of earthbags building. Happy wife, happy life, and all that.

Elijah, I have to advise in my opinion the term "Happy wife, happy life" suggests you are responsible for her happiness!
Which is impossible and incorrect.
I campaign against such language.
have you considered plastering the bags internally?

I am with John about the happy wife etc - IMHO you are on a hiding to nothing with that thinking.  You both need to be happy.  

Our walls are compressed earth.  Some of our walls are plaster smooth and some are rough.  It is depends on how you want to finish the walls.  Our walls were finished with a mix of sifted earth and portland cement.  The rougher walls were bagged and the smoother ones finished with a steel float.  The consistency was about the same as thick yoghurt.   Mixed the dirt the day before and added the cement powder 12 dirt to 1 of cement just before use.

If you do not want to use natural paints, use wallboard paint with 1/2 cup of builders lime per gallon.  This will totally stabilise the wall and the difference between the method you want and wallboard will not be distinguishable except under close scrutiny or you tell them.  Don't seal the tops of the walls or you could get excessive moisture in it, creating collapse.

We use a standard drill bit and wallboard plugs to hang pictures.  In the hallway we have picture hanging track with nylon cords, like the ones used in art galleries.

 Don't seal the tops of the walls or you could get excessive moisture in it, creating collapse.

Paul, where does that idea come from?
Would lime instead of cement been a better brew w.r. to moisture in the earth wall?

John C Daley wrote:

 Don't seal the tops of the walls or you could get excessive moisture in it, creating collapse.

Paul, where does that idea come from?
Would lime instead of cement been a better brew w.r. to moisture in the earth wall?

A couple of things come into play here.  Cement powder is hydroscopic.  If you leave a bag of cement powder it will slowly cure outside to inside. When the bag is opened the cement will, in part, retain some moisture  The second thing is that because you need the wall to cure, it needs to breath.  Our blocks sit on a double row of fired house bricks,  with an air gap between the rows.  Bag walls probably need a water resistant base such as dimensional rot resistant hardwood on fire bricks.  Also, our architect and engineer said not to seal the whole wall because it would fall down.

The other thing with this type of wall is that they need to be well compacted.  From what I have read, use a bat or pick handle and bash it into shape and when is is well compacted, bash and compact it more.  These walls act like a heat pump so there is thermal reactivity +/- humidity.  Our external walls had a silica product in distillate sprayed onto it to shed excess water.  The blocks still get moist if it rains.

Elijah Ravenscroft wrote:I feel like I might be screwing up these calculations.

Mind, the stud wall calculations are on the bare wood, not counting insulation or sheathing or moisture barriers or anything else. But would those things be *that* much more expensive?

Advice? Knowledge? Tips?

We built an 12X18 house last year with 2x6 stud walls. The cost for the wall framing materials was about $700 or ~$12 per linear foot of wall

For comparison to earthbag we built a 10x16 cob cottage with 1 foot thick walls using about 18 yards of sandy loam. Currently, in our area sandy loam with delivery costs around $50 a yard. So, $900 + ~$100 for lime and header material is ~$19 per linear foot of wall.

That being said, I don't think stud wall to earthen wall is a very good comparison. The finishing cost once you have an earthen wall built are pretty minimal where once you have a stud wall up you have significantly more money to spend. With stick built houses the wall framing assembly is one of the cheapest elements of the build. For example, with the 12x18 we spent $2400 on insulation. Granted we used Rockwool comfort board for continuous exterior insulation on the walls and roof but even fiberglass batts are fairly expensive.  

Aaron I dont understand your concept that insulation can be expensive?
It is a product that keeps saving you money for the rest of time.

Obviously good insulation on a conditioned space will pay for itself over time... but initially it can significantly increase the cash needed to start building.

I agree with Paul that the interior of an earthbag, cob, etc. house does not need to be irregular. Just take care when building the structure to keep the interior faces regular and as smooth as practical, and plaster can make them pretty much indistinguishable from plastered stud walls.

I appreciate all the new information I'm getting in this thread, but my main questions at this point are:

1) is it still financially feasible to do a hyperadobe house on a small budget in this way?

2) Even with (necessary) additional insulation?

The most economical method of building is to use the earth in someway and timber obtained free.
- recycled waste
- fallen trees
Anything beyond that is dependant on;
- your skills
- your ability and desire to learn
- your level of funding
- your ability to increase the budget level
- your available resources