Need some advice regarding PSP construction

[TxDirtDigger]

First of all, great forum.  I am greatly impressed with all I have seen here.  Rather new to the computer thing, so if I goof this up - allow me to apologize in advance.  I am interested in building an underground home using the PSP method, have recently ordered Mr. Oehler's book & videos, but have not received them yet.  I have an opportunity this week to assist a neighbor in clearing some trees.  I realize that this is a very generalized statement and the particulars of how deep, kind of soil, etc will affect the materials that I gather, but I can't help but think that there will be some of those trees that will be the appropriate size to use either as posts or girders in construction of my underground home.  Although I would love to salvage all of the trees, time, distance, and equipment just simply won't allow it (besides, the neighbor wants some of them for firewood).  If someone could advise me as to what diameter logs would be the best choices to salvage I would greatly appreciate it.  

[Amanda_931]

No particular idea on exactly what sizes.  But if it's perfectly sound "round wood" is stronger than cut lumber, reputedly because the grain fibers are not cut.  

There may even be a few structural engineers around who know about this.  Ben Law in England found one when he built his house (the making of it was part of a television series--and now there's a book--The Woodland House, available here through--at least--his American publisher, Chelsea Green.  It might be more widely available by now.)

[glenn kangiser]

Hi TxDirtDigger.  

Minimum size is 8" dia for the posts -about 6' or longer is useful.  Rated at 10' avg. Up to 12" or so dia is even better.  Remember that your roof will slope so posts will get longer as you go -multiples of your pitch x 8' spacing -2/12 pitch =16" taller post for second one on higher side. Bays would continue to increase that much.  

Girders 12 1/2" dia in multiples of 8' for 8' spans

Beams 7 1/2" dia min. multiples of 8' length
there are uses for smaller sizes too - closets - intermediate sidewall posts etc.  -grab whatever you can get.

14" girders will allow you to go to 10'6" spacing with 9" posts.  Larger can always be used.

[TxDirtDigger]

Thanks for the info.  I've got a general idea what size to get loaded on the flatbed now.  Now all I need is a cheap (or better yet free) source for planking and poly and I'll really be happy!!

[glenn kangiser]

Cheap but with work attached, try the Alaskan sawmill attachment for a chainsaw.  Cut your own planks.  Note -side wall planks spanning 8' should be 1 1/2" or with post at 4' (4" would do for intermediate) 3/4" will work - hand backfill and lightly tamp per your book instructions.

[TxDirtDigger]

Good idea Glenn.  I'm definitely not allergic to hard work, just always a dollar or two short it seems.  
Now - to muddy the waters a bit - my cousin called earlier this afternoon, I told him of my plans.  Due to the drastic shortage of trees in our area of the world he has been checking into the idea of using earthbag construction underground.  He liked Mike's plans and ideas concerning the uphill patio, etc.  Has anyone out there built or does anyone know of an underground structure where the load bearing walls are constructed of earthbags?  The roof would still be constructed of girders/beams, just held up via dirt bags rather than posts.  Thanks for all the help folks - you're an awesome group of people!

[Amanda_931]

I love the idea of earthbags above ground.  not at all sure about under-....

But, I just went to the OKOKOK productions site, and under smartass answers to questions I found what might be the beginnings of an answer.

I'm not at all sure if this means that Kiffmeyer and Hunter (very likely the authors of the book) mean that you can pile earth up around your earthbag wall, or you should use something like 12" block with surface bonding cement (not recommended by the manufacturers of same, IIRC) and some kind of waterproofing compound and a whole lot of thinking about drainage. until you get out of the ground.  That's about what Rob Roy did with his original house.  Might have to use some serious waterproofing--that won't melt your bags.

I think that in some very dry areas they do use earthbags to provide boots for cob or straw bale structures, on top of a rubble trench foundation.

There's quite a bit of thinking on how to buttress earthen buildings.  Mike Oehler has done a lot of thinking on how to do brace underground structures.  Paying attention to this is important.

http://www.okokok.org/faq.php

What happens to an earthbag house when it rains?

It melts! Ha-ha - just kidding! Just like any other type of house, an earthbag house needs to be designed to suit the climate. The wetter the climate, the more protection the roof should provide to shed rain away from the walls. Extra long eaves and a tall, stabilized stem wall are simple design features that provide ample wall protection. Additional considerations are wrap-around porches and an erosion resistant lime or cement base plaster. Remember, sandbags are used for flood control and designed to be able to endure submergence in water. They resist mold, rot, warping, twisting and termites unlike more common building materials like wood.

What kind of R-Value does an earthbag wall have?

I can't think of a smart-ass answer to this question, but, typically, earthen mass has a very low R-value of approximately 0.25 per inch. But it has a high U-Value. U-value stands for Units per Thermal Radiation. Earth has a high mass value that acts as a thermal storage bank able to absorb warmth generated from inside a building from (for example) passive solar, or forced air, or a wood stove that is then absorbed by the walls. This warmth is slowly released back into the living space helping to regulate the internal temperature in an active style. R-value on the other hand stands for Resistance. R-value is a measurement of how much resistance to change is provided, like that imparted by insulation. Think of a sleeping bag on a cold night. The more sleeping bags you have around you, the longer it will take for the outside temperatures to affect the temperature inside the bag. Mass works best in a climate that has a lot of sun to warm the exterior walls as well as providing an internal heat sink for passive solar application. In a really cold, cloudy location, an earthbag wall would be more effective with insulation added to the exterior walls. This can be done with rigid foam or straw bales attached to the walls. Another way to take advantage of the regulating effect of the earth itself is by berming an earthbag structure into the side of a southern slope or at least sinking the floor level below frost line. As the earth below frost line maintains a stable temperature of 52°F to 58°F, it will never freeze and will use far less energy to heat in the winter or cool it in the summer.

[glenn kangiser]

Beyond what you asked, TxDirtDigger, I think Amanda knows more about earthship type construction --- pounding used tires full of dirt --

I don't know much about it and need to study it more but that could get you a structure to hold up a roof -- tires can be free.  They are plastered over later.

Cob can support a roof and can be made safe with  wood bond beam or various other methods - rammed earth is similar -- all pretty well free.

[TxDirtDigger]

Did as you kind folks suggested, checked out the info on earthbags and also on the earthship construction methods.  I've got a source for tires who laughed and told me I could have as many as I could haul away for the price of buying his lunch at the local hamburger stand.  So, it seems to be a pretty good idea to ram the free tires with free dirt, protect the walls with polyethylene sheeting as we go up as a vapor barrier.  Then top the structure with the harvested trees from my neighbors property.  I have access to a LOT of pallets that I can disassemble for planking to go over the harvested trees (just need to space them really close together to provide adequate support).  then umbrella the whole thing with poly and a light load of dirt.  I have a woodstove if I need backup heat, already have a good well on the property - just divert water into a storage tank upgrade from the structure, let water gravity feed via PVC pipe for water.  I think I can probably piece together a quite usable door from the 2x4 pieces from the pallets.  Now all I need is a couple of windows then NO MORE RENT!!     Thanks for all of the help folks - you're appreciated.

[glenn kangiser]

Sounds exciting.

[Amanda_931]

Back in March I posted this:

http://www.countryplans.com/cgi-bin/yabb2/YaBB.pl?num=1143750607

Mike Shealy makes standard type tire houses.  Quite a bit of information on his site--if you can find it.  The link here shows the foundation he made for a goat shed.  Squishy is how I would put it.  But if what's on top is not too heavy, a whole lot easier to handle than the standard, in which you pound enough earth into each tire to blow it up like an innertube--close, anyway.  I have done steps, one of these years may get a retaining wall done with topless tires.

(it would be good--not easy, but good, to have all your tires the same thickness and outside diameter.  For pretty obvious reasons.  If you could get a whole lot that were the same thickness you might be able to take both sidewalls off and shove them into roughly the same width, with square corners so it might not be the end of the world if you had two seams right above each other.  The Farbers who wrote a booklet about tirecrafting recommend doing walkways and raised beds that way.)

[TxDirtDigger]

Thanks for hooking me up with that info, Amanda.  I like the topless tire idea, it appears that it would be considerably more efficient as far as time goes.  I may try some expirements with this before I begin to build just to see if I feel comfortable with the topless tire walls surrounding me.  I would imagine that walls constructed in this manner are still plenty heavy and strong.  Just have to watch the overall roof weight as you suggested.       Does anyone on the forum have any experience building a watershed roof as suggested by Mr. Shealy?  I am already planning on sinking a holding tank into the ground for water, it would be rather simple to divert roof run off to help keep it full.  The only complication I can see would be the need to HEAVILY insulate the roof in order to maintain home temperature.  Anyone got cheap suggestions for insulating material?  
Wow - our little home sure has undergone a lot of structural idea changes in the last couple of days.  However - I am thankful for everyone's assistance.  If for no other reason than it is mine, debt free, and I built it myself, this will be a very special home for my wife and I.  

[Amanda_931]

If you're in (wool type) sheep country, and people give away or sell substandard fleeces inexpensively, they will make good, reasonably fireproof insulation.  Supposed to be long-lived and immune to moths if it's never been washed or de-lanolinized or whatever.

I've used Cocoon--the cellulose (fireproofed recycled paper I think) that one is supposed to blow in--we didn't.  but I've no idea how expensive it is.  The little that we used wasn't much, but it was a very small area.

[TxDirtDigger]

Another great idea.  Not too far from sheep country - shouldn't be too much of a hassle.  More advice requested - recommendations on inexpensive roofing materials that could be used to build a watershed type roof.  I have seen references to dome roofs being made of burlap soaked in concrete and using it to overlay a rebar framework, I have also seen pictures where native lumber was used to frame out a more conventional roof.  Amanda - I take it you have some experience building a project similar to an earthship.  Do you have any pics posted of your home? Appreciate you folks continuing to share your knowledge, experience, and good advice.

[glenn-k]

In India they have made structures reinforced with Hessian- similar to burlap that span around 60 feet and are a total of about 2 inches thick.  They are made over a wood frame that may later be removed.  I'd suggest careful testing of this since you won't get it engineered I'm pretty sure and concrete is heavy.  Concrete requires 7 days to gain most of it's strength.  Heavier framing underneath it would be wise until you have or find more information to go on.  Don't forget about snow loading - I've even seen snow in Texas, as I seem to remember.

[TxDirtDigger]

Wooden framing would be stronger and likely easier to do.  I personally don't think I will pull it out once the dome is formed though.   Other than the weight, I don't see that the wooden bracing would hurt anything do y'all?  Thanks again for all the help - off to clear some trees.  

[Dustin]

If you haven't read the Earthship books and are contemplating using tire walls, I would suggest you review them. You need to create a concrete bond beam over the top course of tires.

[Dustin]

Here's very interesting link on earthen construction:
http://radio.weblogs.com/0119080/stories/2003/04/09/theMythAndPromiseOfDirtChe.html

[Amanda_931]

Yes it is interesting.

He doesn't talk much about local materials.  That's slowly becoming an issue here.  Tony Wrench and Ben Law talk a lot about it.  (Wales and England respectively, IIRC).

And his favorite, pumice-crete, is the one most likely to require lots of transportation of rock.  Even if it is light weight rock.  Sure ain't much around here.

The earth block machines may be a pretty good idea.  The one I've been thinking about, coming out of Decatur Alabama, produces a nearly 30-pound block that is only about 8" x 4" x 12."  I think that's quite a bit denser than the manual earth block machines--Cinva Ram or the one from Auroville.

There have been discussions on the coblist about ways to build faster, whether tractors, tillers, or cement mixers help or hurt.  On very small buildings slumping can be an issue--you get round to your starting point before the stuff is dry enough not to bulge with the next layer.

Nader Khalili of Cal-Earth believes that the "superadobe" houses the size of the ones on the site can be put up in a day, and could stand not being plastered for a week or so, for  emergency housing--and that all you'd have to do to get people started would be to airlift in the bag stock.