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Easiest way for one person to build a small cabin  RSS feed

 
Rick Kruszewski
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I would like to build a small cabin of 800sq ft or less and 95% of it will be by myself. I was thinking of earthbag or straw bale but am open to anything, preferably natural. What would be the easiest and quickest method? Probably in the Rockies.
 
Dillon Nichols
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Pretty open-ended! Can you provide more info?

Who are you, what is your experience, physical capacity...?

What tools/equipment do you have? What can you rent in the area?

What materials are available at your anticipated site? Timber? Suitable soil for cob, earthbag? Clay for plaster?

What is the intended purpose of the building? Full-time, vacations, etc...

Budget?



Fast, good, cheap... pick 2. Or if you screw up, sometimes just 1, or even none...


See how much smaller than 800sf you can go, to speed things up. Consider how you will be able to expand later on, when doing the initial design.

For speed a shipping-container setup would be PDQ.

If the terrain is on your side and you can have someone come in with heavy equipment, a wofati could also be quick.

If it was me, I'd think about buying a camper, and building a rough roundwood roof. Move the camper under it, then build an earthbag structure under the same roof. Do a better roof of seasoned timber some summer down the line.
 
S Bengi
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Six big rooms in a 2 by 3 configuration.
Each room is 12ft by 12ft.

Rubble trench foundation.
Perlite or rice hull 'earthbag'
Metal Roof
Stone Floor





 
Dillon Nichols
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I like that layout. Plumbing kept nice and tight. Reasonably minimal space wasted on hallways. Well placed woodstove.

You could easily leave off the 2 bedrooms on the right, and as long as you leave an appropriate doorway, they could be added on later if you actually need them. Ditto on the left, that side door could feed an expansion.


What sort of insulation under the stone floor?
 
S Bengi
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For floor insulation I would use perlite instead of rice hull.


Checkout these guys.
http://breathworkstudio.blogspot.com/2010/08/perlite-insulated-floor.html
 
Rick Kruszewski
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Will perlite be structurally sound in earthbag type construction?
 
Terry Ruth
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It's not the most robust material properties out there for load applications, more for moisture and insulation, unless you add cement or a binder then you can get the compression and other mechanical properties up. Alone it looks around 50 psi, compared to concrete used in basements and footing's 3000+. It do well with MGO to aerate or a filler to cut cost since it is much stronger than portland cement or lime.

https://perlite.org/library-perlite-info/construction-perlite/Perlite-Concrete.pdf
 
Dillon Nichols
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As I understand it, the rigid foam boards used under concrete floors have what seemed to me implausibly low compression strength; 3000PSF, about 21PSI. The concrete above spreads the load over a large enough surface that is fine.

So depending on what's above the perlite floor-bags, I'd think 50 psi should be more than enough for the floor.

If you were thinking of it for a wall, perhaps a double-walled setup with perlite bags on the outside and standard on the inside, providing insulated thermal mass? Definitely a lot of extra work though!
 
Michael Cox
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800sf also doesn't sound very small for a "small single person build"!

Play around with some floor plans and see if you can compress the floor area you need. Bunk beds for more compact accommodation? Or a bed-shelf above the living space in the rafters? I've seen these and they look pretty great - a ladder up to an elevated sleeping platform.

Does this structure need to pass building codes in your area, or are there some simplifications you can make?

Paul's Wofati design has a lot going for it, but it needs earth moving equipment and a couple of people for safe placement of timbers.
 
Terry Ruth
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Dillon, it depends on the foam product. If you look at the specs the manufacture will rate compression at 10% deflection and also call that load "yield strength" or where it cracks. Of course we do not want to design to this load. A 25 PSI rated board now has a compression rating of 8 PSI with a safety factor of 3 for the foundation, 2 for walls, roof, everything else is norm. A smart Engineer would use 3, not 2. Slab on grade concrete can deflect 12% and put more compression load in certain areas of the foam. It will not be even load distribution also due to higher deflection at the 4x8 seams, since it is not monolithic like rockcrete (perlite, vermiculite, scoria, pumice, etc) . A monolithic perlite slab on grade as seen in the table can get a compression strength as high as 2800 PSI with shale in it, it yields when that load is applied to 3.2 ft3. So even if we apply the same SF or 3 we have close to 1000 PSI plenty for a floor and footing with an r-value of about 1.5 per inch. Foam has a higher r-value of 4-8/inch but does not have the mass and hygroscopic properties that make rockcrete a much better choice, structurally, thermally, vapor/water wise. Also, foam is a barrier that can cause pressure differentials between the upper and lower slab causing a "dynamic" load in addition to dead or static.


You also will not find any foam mechanical property of "creep" or deformation over time is another compression combined load that can be permanent, since the foam will not regain it's shape. The low deflection, creep, compression allowables can produce cracks, holes, that can wick and store water, combined with fire retardants, blowing agents, create mold, rot, fungi etc....Some Engineers will completely ignore this, perhaps because it is rare that a slab will get dug up and their liability risk is low, supporting the foam industry. It is faster to throw down some foam and plastic vs mixing a rockcrete in a motor mixer, and perhaps cheaper. The only way out of it is a suspended slab that cost more and would perhaps equal out a slab on grade with perlite.

None of what I said above applies to perlite in a bag, it has higher deflection, higher compression, high creep, than foam...not all good. Perhaps fine for a floor if you infill with clay or cement. You'll hear arguments that foam compression is higher than the soil so all is fine, not true, soil-foam-rockcrete distributes load differently, long story.

There are better materials for floors and ALOT to learn to get them correct needing another thread of it's own.

The easiest method for building a home depends on local resources and skills. Outside of that in-depth knowledge of how to mate materials.





 
Dillon Nichols
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Thanks Terry, very informative.

Terry Ruth wrote:None of what I said above applies to perlite in a bag, it has higher deflection, higher compression, high creep, than foam...not all good. Perhaps fine for a floor if you infill with clay or cement.


Can you expand on the not-good aspects?


Terry Ruth wrote:There are better materials for floors and ALOT to learn to get them correct needing another thread of it's own.


Would definitely be interested in such a thread, I think a lot of others would be too...
 
Terry Ruth
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Dillon, that is challenging part of natural design compared to mainstream that lack of mechanical and thermal properties. Although I compare foams lack of creep data, I did not see any on perlite either so I used my intuition for monolithic vs 4 x 8 sheets with the data I had. Unless there is some mechanical properties of bags of perlite on a floor we have to guess, I did not see an actual deflection property either, just a volume compression applied to. My intuition tells me that bags of perlite will flex or the flex modulus will be low, as compared to foam, but I am not sure. Take both at it's end and try and bend it to get a feel for max deflection and flex. It's probably fine for floors, but should not be put in high bending or the bag will tear at some tensile allowable (limit or yield strength, max deflection, flex load) unless it is kept from going into bending with some cement or well distributed slab above. In most situations you need all the mechanical properties to check all the different combined load cases for failure.

Perlite is made of mined volcanic glass that contains water by the rapid cooling of lava. The moisture absorbed vaporizes explosively when heat is applied. Light gives it white color. It retains water on it's surface (vermiculite retains more) and air in the spaces between giving soil oxygen and moisture retention and drainage properties better than vermiculite which could be valuable under floors-slabs with high water tables and water content. On average around 25% mixed into soil. Perhaps a split mix of vermiculite and perlite although finding have shown asbestos in vermiculite. Both are sterile and inert.

Does not make a whole lot of sense to put them in bags above soil to me anyway that looses some of the properties in soils. With an average ground temp of 55-65, colder in some climates, the insulation value could be enough to prevent cold condensation on a slab, since it is inert no worry about fungi like foam and plastics. As a sub slab lite concrete aggregate with lime or MGO makes more sense, MGO would be much stronger of a binder than portland cement and not conduct magnetic fields, radon gases, or thermally bridge at all like OPC needing no aggregate, or low density cement wood chip board from Durisol or Faswall which is clay neutralized wood-cement. Some perlite in the soil may be good anyway.

There are ways to design breathable floors and slabs, dry moisture with the proper air channels and barriers for radon gases as well. Perhaps I'll start that thread soon. I'm still looking into solar passive and active designs that incorporate human physiology that changes the game and myths substantially!
 
Dan Boone
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In the sub-arctic boreal forest where I grew up, "small cabin" means a 10x10 structure built of small black spruce logs (as small as 4" diameters, though 6" is much better and 10-12 inches is preferred if you can find enough big trees). One hard-working man with a bow saw and a good axe can build one in a couple of weeks if he leaves the logs unpeeled or is lucky enough to have found sufficient dry barkless standing or recently-fallen burn logs. Use the small pole ends of your trees to build a roof, cover it with moss for insulation plus earth on top. (A layer of Visqueen -- once the most common brand of polyethylene sheeting -- is cheating from a natural-building perspective but will greatly reduce leaks, and is at this point almost traditional.) A handful of long spikes is helpful, but not essential; you can build with zero nails if you must. Flooring can be as simple as the native dirt, but half-logs with the flat side up, notched-in to the bottom course of logs, will be much preferred (a few day's work with a chainsaw, not easy by hand unless you have two men, a crosscut saw, and a sawyer's pit.)

This is temporary or survival housing; the earth-and-pole roof will start to collapse inside of ten years. The walls themselves will stand until the bottom logs in contact with the ground begin to rot. A typical response is to jack up the cabin one edge at a time and replace just the rotted logs when that happens. Obviously any sort of foundation fancier than "a square trench scraped in the moss" will help by keeping the bottom logs from contacting moist soil; but in permafrost country there may be complications. The standard primitive cabin will sort of "float" as the permafrost melts but will usually stay more-or-less level; more complicated foundation systems tend to have more failure modes as the ground shifts.
 
Terry Ruth
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That sounds like the same home Daniel Boone built back in the early 19th century....Ha Ha. I bet the deed would free and clear. There is alot of wood in the rockies, not sure about black spruce although I have read good things about it's ability to manage water and vapor, store heat and cold. So an earth floor with radiant heat from a masonry heater fired by wood or natural gas or wall mounted cast iron baseboard radiators. I'm a big fan of rooftop solar collectors and sun facing windows with overhands and trees to manage overheats, low e-coating west windows to reflect heat. Id run solar collectors to my walls in micro-tube mats not floor tubing to get more even heat distribution to the human body vs through the feet. I'd use an earth plaster inside to take down any thermal bridging of wood and air seal since it does get nippy up there in the high mountains in winter, and some water and ICE membrane to stop ice dams.

I'd use rock or something between the wood and soil to stop termites, since as we go south west in the US termites get to be a pain. A glass bead spray reflective paint inside the roof will keep it cool in summer. A flat roof high in altitude I'm not sure about snow loads and drainage. If you go solar or off-grid you need a gable or hip or the right angle check some solar calculators to the lot. Slate or cedar roof tiles, magnesium sheathing (dries very fast) non conductor of heat, inert, sterile, taped seams, water and ICE 6 feet up from fascia, no OSB. Slate or Shake roof tiles last 100 years, great for rain catchment. I'd put a raised heel in the roof and insulate it, attached to large over hangs (90% of water issues at foundations are solved by). If I were to use a plastic membrane for the roof I'd go with a one piece for something this size like Duro-Last.

Another way to do floors is with wood chips, MGO, and a clay mix. I'd put an air gap in my roof and foundation to take care of radon gasses, french drain, no crawl run plumbing in floor and insulate it and heat it or keep from freezing.

Don't forget the skies and save me a chair for the winter x-games
 
Dan Boone
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Terry Ruth wrote:That sounds like the same home Daniel Boone built back in the early 19th century....Ha Ha. I bet the deed would free and clear. There is alot of wood in the rockies, not sure about black spruce although I have read good things about it's ability to manage water and vapor, store heat and cold.


Most people I knew were building these on government land, just squatting. This was in the 1970s mostly (before ANCSA, the Alaska Native Claims Settlement act, was passed or fully implemented) when Alaska was like Nevada, all government land and no private land hardly at all.

There was no special merit to the black spruce except that it was widely available. White spruce grew taller and thicker and was preferred for building permanent log homes, but it was much harder to find sufficient large straight specimens.
 
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