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Quonset hut build

SoCoJoe | Posted in Green Building Techniques on

Ive been lurking here for some time and have learned a lot. I have purchased a used Quonset hut used and am planning on building it next year. There are no building codes which prevent the techniques I am proposing in the county in which I am building. I would like feedback regarding this design.

San luis valley. Climate zone 7. Money is very tight.

The q-hut is a steelmaster 15ga. It is designed for massive snow loads, Antarctic and such.. Some of the more adventurous have earthbagged entire q-huts with scoria. Im afraid Im not that brave even though the building is rate for those loads. However berming is a well proven practice that has a long history. The hut arches is comprised of 5 panels four 10 feet in circumstance and one two foot in circumference.

The individuals I bought this steel of of built a home with the same steel. The 2 foot panel is on top all the way across not changed around to provide breaks in seams on their home. Their design was engineered by a professional. I would prefer to use the two foot piece so all the seams are not at the same place but the design I propose precludes that and the engineered building that the individuals I purchased this steel off of building is built with the two foot portion at the top all the way across.

. The arches will be assembled with a thermal break in that first seam. both sides of the hut, probably Kevlar cloth as it can be found cheap is tough and good insulator. Stainless eyes (eye inside) will be installed on that first seam at two foot intervals where the archs overlap with large backing plates.. Using proper leveling washers/turnbuckles/ shackles/swage eyes 316 1/8 1×19 . aircraft wire will be pulled tight from the eyes on both sides of the building. Cost for all that is about $150. This actually makes a incredibly strong building even stronger.

Using OSB (repurpoused $5 sheet) ill cut a flat piece that matches the contour of the arches . about a foot wide. ill lay it flat along the edge of the archs on top of the ends of the wire. Illl polyurethane caulk this piece of board to the q-hut steel ( which will cost me). This will provide me with a way to try to get a continuous. vapor barrier by allowing attachment of a vapor barrier to the steel.

I have a quantity of 5mm basalt grid. It is a very fire resistant material. The grid I have is 1 meter wide. starting at one side of the building alongside the arches one meter of grid is placed on top of the wire and secured with cable tyes. I have been picking up fiberglass insulation. It can be found very cheap from leftovers from large construction projects. Ive been getting unfaced. and have the 700 cubic feet I need for the ceiling.. 6 inches of fiberglass roll is placed on top of the basalt grid. Now kraft paper is placed on top of that insulation and sealed to the osb that was caulked to the side of the hut. I plan on using aquabar b craft paper. It calls out .7 perm. I plan on using beeswax/mineral oil as a sealant. Another 6″ of fiberglass is placed on top of the kraft paper. Now the process is repeated across the whole hut sealing each piece of kraft paper overlap to the next with bees wax/mineral oil. The last portion will have to be put in place from the top with planks suspended from more aircraft wire. Then the basalt grid and the bottom of the fiberglass is shot with three our four coats of latex paint. Ive played with this the latex paint binds everything up nicely.

This gives me a insulated ceiling. I calculate the safety factor of the load on the wire rope and fasteners at 50 – ten times a normal safety factor. The basalt grid is rated at 900 centigrade which exceeds normal house fire temps. Its got 6″ of glass on top of it before the first fuel the aqubar b kraft paper

No stud load. No drywall load. No OSB load(except the foot on the edges). Rather fire resistant. Safety factor of 50 from a mechanical support perspective.

The vapor barrier is in the middle of the glass both to prevent it from being a ceiling fuel and to ensure it does not condense vapor. The glass also protects the kraft paper from pokes that invariably occur in walls. The plane that the aircraft wire provides allows for continuous vapor air barrier in this ceiling. No vents. no overhead fixtures. A nice soft ceiling flexible ceiling that will accommodate the thermal behavior of the exterior steel. The structural support for the ceiling remains observable and the turnbuckles can even be adjusted if needed

The ends of the q hut get scoria bagged to the 1 foot above the ceiling plastered, then osb for the top part of the ends with lots of vents for the “attic”. The hut panels are unsealed all the way around so basically the whole exterior shell breaths also.

Now the Exterior of the hut is scoria bagged and plastered to one foot above the first seam. Stopping there puts no load on the roof, the horizontal inward load is limited by the vector and actually makes the building stronger (again). This put the ends of the wire rope inside the insulation so no thermal bridging there. A gutter is formed at the top of the bags with reinforced membrane (pool liner repurposed) and covered with plaster. The interface between the bags the gutter and the steel will be tricky but I think it can be done with polyurethane caulk. Really no different than the sealing that always has to occur between the hut and the footer.

To recount
Ceiling continuous vapor barrier .7 perm.R 48
Sides of hut unsealed metal panels to scoria bags and plaster- total assembly 3 -4 perms? R32 (16″)
Ends of hut scoria bag plaster both sides 2-3 perms? R32 (16″)

Im very comfortable with e mechanical aspects of the design.

My first concern is whether the thermal break at the first seam of the building provided by Kevlar cloth will be good enough. Those pieces have to be bolted together tight so I cant put soft foam or something of that nature in between. I know i will lose some heat there but how much…If that thermal break is not sufficient and I bridge a bunch of heat down into the steel wall it means Im defeating both my glass in the ceiling and the scoria on the exterior.

My second concern is whether Im going to end up with a sodden wad of fiberglass in my ceiling because Ive missed something and there is a fundamental flaw in regards to the designs winter vapor control.. My hope is that in the summer when the steel cooks in the sun the glass will dry out, to the inside, the scoria will dry to the inside, reversing whatever moisture vapor drive put there in the winter.

My third concern is that the design allows very little ceiling access for whatever may arise all i will have is a suspended plank in the “attic”

Feedback? Im pretty adventurous but I thought it wise to seek the knowledge here.
Thank you

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  1. GBA Editor
    Martin Holladay | | #1

    Please -- post a sketch.

  2. SoCoJoe | | #2

    Hi Martin.;
    Thank you for your reply. I dont own a scanner. What aspect did I not communicative well on?

  3. SoCoJoe | | #3

    Hi Martin;
    I made a Very rough sketch and shot a photo. The proverbial cocktail napkin :)

  4. Expert Member

    I'm not sure i completely understand either but two areas stand out as being problematic.
    The intersection of the arch and the built-up base. You characterize it as being similar to what would occur at the footings, but it is different in several respects. Quonset huts generally don't rely on caulking at the base. They are either imbedded in trough formed in the footings which is later filled with concrete, or attached to a base flashing which mirrors the shape of the arches. The metal expands and contracts with temperature change. I thin you need to look for a more reliable way of sealing the covering membrane to the arches.
    How does you stack-up deal with the condensation that will occur on the outer-skin? It can't dry to the exterior, so you need some way of keeping the outer skin warm enough that there is no condensation. As it is i fear the fiberglass will become sodden quite quickly and have no path that will allow it to dry.

  5. Expert Member

    double post

  6. Expert Member

    Ah - I see. From your sketch it appears you don't need to worry about my second concern - although you are still going to have a fair amount of condensation in what you call the attic which might be a problem.

    I'm not sure how you could incorporate a thermal break either. that's a tough one.

    Adventurous might be a good way to describe it. I've built a few quonsets but have no experience with scoria bags. It will be interesting. Good luck.

  7. SoCoJoe | | #7

    Malcom Thank you for your feedback I apreciate it! Yes creating a watertight gutter at the top of the scoria bags is a concern, but I only have to get it over the lip of the mortar into the pool liner gutter.. I think it can be done. Any snow slide into the gutter wont have much velocity at that angle. with any luck it might keep the snow on top longer which makes for a very warm house. Polyurethane bonds strongly to galvanized especially with a primer and of course bonds to the mortar ramp i will make into the gutter also. While stopping the bags at 9 feet does create a obstruction to water flow it also create a gutter. Stopping the water there goes against the principle of working with the forces of nature rather than against. Stopping it there does not use the the design of the hut which is designed start to finish to shed water The positive is the roof rain water and snow melt is now diverted from the soil around the footers. And when the water gets to the bottom it still has to be dealt with anyway. Yes the bottom gets grouted into the u-groove but its still a concrete/metal intersection that has to get sealed. I see the difference between sealing at the base and sealing on top of the bags as being a difference of being about 45 degrees. That 45 degrees definitely favors water intrusion rather than a straight right angle at the base. At the base the water has to go all the way around the grout to intrude but on top of the bags it just has to get past the lip of the gutter and its into the earthbag cavity.This and other aspects of the design have potential to turn into endless repair which is why Im here asking for feedback.One alternative is to build a ramp at the top of the earth bags and let the water flow over the earthbag plaster but my preference is to start to handle it there. That seal does have to work . Cold water running onto that lower panel is the ultimate thermal bypass. What say you GBA too problematic to implement? Thank you again for the feedback Malcom.

  8. SoCoJoe | | #9

    One more time...

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