Natural Building Blog

Earthbag Building & Other Natural Building Methods

Hypar Roofs

Wooden frame on Hypar roof

Wooden frame on Hypar roof

 

Stretching mesh over the Hypar roof frame

Stretching mesh over the Hypar roof frame

 

Hypar roofs are lightweight enough they can be built on the ground and lifted into place.

Hypar roofs are lightweight enough they can be built on the ground and lifted into place.

George Nez pioneered and wrote the book on hypar roofs, along with Albert Knott. They’re extremely durable and practical, and have been used around the world for decades. This is the same type of roof used on the Free Burma Ranger Clinic posted earlier.

The basic process involves building a wood or bamboo frame, stretching nylon plaster mesh over the frame and stapling in place, and then coating the roof on both sides with a slurry of Portland cement and latex/acrylic admix. FlyingConcrete has more information on their site.  Or you can buy George Nez’s book Latex Concrete Habitat at Amazon (currently $18).

Roofs for the World
Image source 1&2: Nez Roof Construction 8/2004
Image source 3: Ben Vander Plas
Video of George Nez explaining the concept
Flying Concrete http://www.flyingconcrete.com/hypar.htm
Free Burma Ranger hypar roof album
EarthbagBuilding.com project page about the Free Burma Ranger Clinic

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16 Responses to “Hypar Roofs”

  1. Craig from Maine says:

    Hi Owen :)

    I noticed this Instructible :

    http://www.instructables.com/id/Latex-Concrete-Roof/

    Is it contextually contributive ?

    If not, you can simply delete this post LOL

    Rock on !
    Craig

  2. Owen Geiger says:

    Update from Ben:
    We definitely learned a good amount through the process of building, especially through mistakes along the way. We found working in heavy rains is not a great idea, and saw how difficult it is to tamp saturated bags. While story poles were used for each corner, it is important to keep a close eye on them as the walls go up – we had problems with corners coming out gradually and pushing on the poles. Since we ran out of road base before finishing we ordered a new truck load. Unfortunately a different type of soil was delivered and this caused some problems with the bags on the upper courses being tamped out flatter, making some inconsistency in the walls. The earthen plaster we made was just excavated right from the site and we added some lime. We used ripped up rice bags to use as the fiber in this plaster and it seemed to work well. On the outside a lime plaster was applied to finish it off. The team didn’t have enough time to finish the sub roof to provide an overhang to protect the walls, but we got more done than we had hoped in 9 days.

    It looks like the whole project came out to about $5000, including all the tools and different materials for experimental testing. The building ended up being about 4 m X 8 m. The HyPar roofs were 4.5 m squares.

  3. Milton says:

    I would think this would be a useful method with a Grancrete or Ceratech product. Using a thin layer of flyash based cement would make it much stronger then a portland based product.

  4. Abe says:

    We built a hypar/latex acrylic concrete roof on our CEB bedroom addition:
    http://velacreations.blogspot.com/search/label/latex%20concrete

    We found it very easy and fast to work with, but there are some tricks.

    First, make sure you can find the latex. It is not as widely available as implied in Nez’s book. We eventually found a few sources, and they all ranged in quality, so it pays to do some tests beforehand.

    The mesh can be a lot of different things, but a 30% shadecloth should work really good.

    You don’t need a sprayer, just pour and brush the mix on. It goes really fast. We made a 400 sf roof in less than 4 days with 4 people.

    • Owen Geiger says:

      Great, thanks for sharing. Glad to see some detailed directions with photos. And I see you said “we think we have found the way we will do roofs from now on.” So that’s a good recommendation.

      • Abe says:

        Well, we said that at the time, but we are still exploring options. The cost is not nearly as low as reported in Nez’s book or online. We figured $3/sf for the roof plus structure. There are some things we know to reduce that cost, but when metal roof is $1.50 a sf, it makes it hard to compete financially. The acrylic/latex is not cheap in our area, but we are still exploring options.

        I think Microconcrete Roof Tiles might have potential here as well.

        We have done ferrocement roofs, metal roofs, and acrylic concrete roofs on this house. Each has their advantages and drawbacks. I prefer concrete-type roofs for the unique shape and noise reduction. They also seem to have a much longer lifespan.

  5. Dustin says:

    Couldn’t a more conventional roof shape be used?

    Or…. A more open mesh weave wrapped around a 3v Geodesic conduit/basalt rebar skeleton, shotcrete/geopolymer or maybe even trowel it on…. A la ferrocement? The idea of a roof being a separate element from the rest of the building has always seemed un-natural and contrived to me. But, it does aid it water catchment.

    No… Gravel bag “ring beam” with basalt rebar sticking straight up. Bend them inwards (basalt rebar is ‘springy’) to a point. You now have Catenary Dome Skeleton. Wrap. Squirt/brush/trowel. Wait. Backfill. Win.

    • Owen Geiger says:

      This was an extreme situation where all supplies had to be carried by hand about six miles if I remember correctly. Future clinics in Burma may be even more remote. I imagine this was a driving force in arriving at this design.

  6. chaburchak says:

    Any idea whether the acrylic/cement mix would be thin enough to work in a Tirolessa sprayer?

    • Owen Geiger says:

      I think it would work, except the process would be very slow. It would be much faster to roll it on. You can pour buckets of latex cement through the vent hole to coat the top portion.

  7. Karisa L Vaughn says:

    What is the estimated cost for a roof the size of the one in this example?

  8. David Reed says:

    We will be building a Hypar roof on the Wicosani Experiential Center, in Pine Ridge next year!!

    • Owen Geiger says:

      I helped build a strawbale roundhouse with hypar roof in Pine Ridge. You can still find a few pics if you search Google. The roof worked out great with wide overhangs on all sides. The hypar was built first and this enabled us to work in the shade and out of the rain on the rest of the structure. Unfortunately, I just learned the area was flooded and the building destroyed. What a shame. Maybe the roof survived and was reused.

  9. Owen Geiger says:

    The hypar is based on “building roofs first” — build the roof first to provide quick shelter from the elements, and then build the walls later. This concept evolved out of humanitarian work on UN and USAID projects.

    Other benefits: no power tools needed, earthquake and hurricane resistant, holds up in extreme heat and freezing weather, withstands heavy snow, can be mass produced, can be joined modularly to create larger structures, good ventilation (vent can be covered), creates loft space…

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