This is my second post about hempcrete in just a few days. Obviously I’m pretty excited about it. The last post listed quite a few advantages of hempcrete. This post with even more exciting advantages is based on an article in the most recent issue of The Owner Builder magazine called Growing Your Own House, by Hilary Fuerst. Hilary attended the first ever hempcrete workshop in Australia that sold out with over 50 attendants. (That’s very high for a natural building workshop.) Part of the reason for the strong interest is because growing hemp is now legal in New South Wales, Australia. There’s also a new book out (talk about perfect timing!) by Steve Allin – Building with Hemp that sounds really good.

Hempcrete is simply a mixture of industrial hemp, hydrated lime, sand and water. One key advantage of hempcrete is it is repellent to white ants and fire ants, which are a major problem in Australia. They’ll attack wood, straw bales and earthen structures such as cob and adobe. Hemp walls ‘breathe’ or allow moisture to pass through, discouraging the growth of mold. It’s carbon negative because it sequesters carbon when used as a building material. Hemp produces large quantities of fiber faster than forests without fertilizer or pesticides in most any soil, and is rapidly renewable. One 3-4 month crop on one hectare can produce enough hemp to build a 135 square meter (1,450 sq. ft.) house and small shed! It meets building codes, is fire-resistant, non-toxic, has good insulation properties and is simple to work with. The advantages go on and on. There’s even a centuries old hempcrete building in Japan that’s still standing.

There are three drawbacks to hempcrete in my opinion: 1. it’s not loadbearing — a frame is required to carry the loads, 2. forms are needed, which must be raised as you build, 3. it’s illegal to grow hemp in many places, so you’d typically have to ship materials from far away, thereby adding to the cost and environmental footprint.

However, I think there’s a simple solution to each of these drawbacks: 1. fill earthbags with hempcrete or similar mixture — wide earthbag walls should provide sufficient thickness to carry single story loads on small, simple structures, 2. earthbags would eliminate the need for forms and form work, 3. use vetiver grass instead of hemp, which also repels insects such as termites and is rot resistant. I haven’t worked with hempcrete yet, so my opinion is largely based on conjecture (with a lot of related building experience thrown in). More testing is needed. Anyway, I see a bright future for all these sustainable building systems, including earthbag, hempcrete and vetiver.

Want to learn more? Here’s another good hempcrete video that claims it is stronger than concrete and one sixth the weight. Madame France Pierre, a hempcrete builder in France, constructs about 300 homes a year using this material. She says it petrifies and turns to stone. She has thousands of orders, but is limited by the availability of hemp.

More good videos:



Comments

Hempcrete — Growing Your Own House — 27 Comments

  1. I would like to know if hempcrete is suitable for extreme weather conditions?
    If I would like to build chalet on water(sea) is there any formula?

  2. I’m looking for quotes to build a handicap accessible ranch style or better yet geodesic dome home constructed with hempcrete. Also a basement with as little a Co2 footprint as possible. Plus it will be water tight for many generations. Also I am interested in incorporating thermal rocket mass heaters. A combo kitchen you can cook with wood and electrical equipment. I want to install solar and wind turbines for main electric. Indoor greenhouse for the southern part of the house and kitchen area. I have other ideas. But the most maintenance free I prefer.
    My wife and I are taking care of our youngest daughter who is 29, but she is physically and mentally handicapped, plus we are raising three teenage grandchildren and we are limited on funds. I have cardio myopathy and looking to build a business in aquaponics. So any finance assit5ance would be most appreciated.

    Thank you

    Will

    • I don’t want to discourage you but custom homes like this are often more expensive than conventional homes. I don’t know of anyone building homes like this. Almost no one will be able to help you. In general, simplicity is key. Start small and keep it simple. Allow for expansion and add on later. And if you don’t have a strong labor force, choose methods that require less labor.

      • Because hempcrete is a breathable material it cannot be made 100% waterproof, and would therefore not be suitable for a geodesic dome design. Ideally a hempcrete wall would be 12” thick encompassing a 2×4 stud frame wall. The design should include a minimum of 24” eves. Materials plus labor is $24 a cubic foot. Lime finish plaster runs $12-$20 a square foot.

  3. I’ve also been thinking that earthbag hempcrete hybrid might work really well. Probably hyperadobe mesh bags would be the best. Looking forward to seeing what you do with this!

  4. OK! I have designed my home and want to incorporate hempcrete in an earth sheltered home. Problem is, I found out that hempcrete can’t be used underground? Is it possible to make it work while not worrying about it biodegrading due to soil/moisture. I plan on building in the mountain range of Santa Cruz/San Francisco. Insight is much appreciated! Once that’s received, it’s onto finding an architect to make my CAD become a reality. Do you work with any or recommend? Thanks

    • Yes, keep organic materials such as hemp and straw above grade. One option is to use earthbags/gravel bags up to windowsill height. Then use hempcrete, etc.

      Here are my plans. Take a look and see if anything is similar to what you want:
      https://earthbagplans.wordpress.com/

      Your biggest challenge will be dealing with codes. CA has very strict codes and they will try to squash most anything alternative.

    • It all depends on what natural materials are available and make sense in your area. For example, one lady contractor in France is using hempcrete to build high end houses that turn to stone! She can’t keep up with demand. The story is here on our blog. It seems she has discovered a type of geopolymer formula that becomes rock hard without cement.

  5. We have a house covered with blue board (8mm compressed fibre cement). We are wanting to render it and are hoping there may be a hempcrete solution available..
    Can you please give me a rough price guide and any info on where we may be able to obtain the materials needed??
    Thanx heaps
    Leonie and Tim..

  6. Do earth bags breathe like hemp crete does? If not I think I would chose a different type of bag. I think the building between forms provides a more solid house that is sure to stand the test of time. Also building with the forms provides for a house that ultimately would be more aesthetically pleasing and therefore easier to sell if you chose to sell it down the line. But all the power to you. I’d buy the book and read it before I started ANYTHING just in case. As the one lady says… enthusiasm is there but confusion abounds. Why spend a lot of time designing and building a home only to have it rot or fall apart? And losing the moisture transfer is a real downfall if the hemp where put in a plastic bag.

    • Yes, moisture can pass through earthbags because the fabric is woven. However, durable plaster on the exterior means very little if any water gets into the wall. Earthbag is very popular in tropical/rainy climates and we haven’t heard of any problems so far. (The main problem is building domes in rainy/snowy climates.}

      Design for the long term like you say. That’s one of the key benefits of building with bags. It’s similar to rammed earth that can last thousands of years, but no forms are needed. Search our blog for Ancient Rammed Earth for amazing examples.

  7. I’ve always thought that hempcrete was so interesting because of how natural it is. Very cool info about the building in Japan. Thanks for posting.

  8. Hi, i will go to australia in order to build a house, where can i find hemp and lime for building, what is the price in australia. Thanks

  9. USA hurd suppliers, who have sales and pricing information for hurd used in hempcrete in the USA are below:

    American Hemp (http://americanhempllc.com – East Coast, USA hemp distribution and sale),
    Hemp Traders (http://hemptraders.com – West Coast, USA hemp distribution and sale)

    More information about hemp for grain and fiber, especially in the USA, can be found on the:

    Hemp Industries Association (http://thehia.org),
    Nutiva (http://nutiva.com – hemp food),
    Manitoba Harvest (http://manitobaharvest.com – hemp food),
    Vote Hemp (http://votehemp.com).

    The hemp industry could be viable in the mass production and sale of hemp fiber, hurd (core), dust, and grain for the food (grain and oil), building materials (hempcrete, insulation, fiberboard, etc.) animal bedding (equine/horse, guinea pig, poultry, etc.), clothing, bioplastics, etc. industries.

  10. I am interested in finding out information about availabilty and costs of using hempcrete in house building in NSW. I am on the Central Coast of NSW. I am keen to build with sustainable products. I read that hempcrete can be used as an infill for suspended timber floors to provide insulation and thermal regulation. I would rather this than use heaps of concrete for the floor.
    Any information would be gratefully received.

    Thanks
    Carolyn

  11. My name is Klara Marosszeky and I ran the first Australian hemp building workshop at Byron Bay that you refer to in your article. I have a small business called the Australian Hemp Masonry Company. The goal of my research at UNSW over several years was to develop a reliable affordable hemp lime building material so that we don’t have to import a binder from the UK. The carbon footprint of that is enormous.

    I would like to voice my concern over the patching together of accurate and inaccurate information about hemp building which is occurring increasingly on the net. Unfortunately the industry seems to have attracted a few entrepeneurs who have not necessarily built with hemp, who promote themselves as hemp building experts. Others then extrapolate on information taken from them, rather than sourcing actual research. From corresponding with Professor Tom Woolley, who I consider to be the primary expert in hemp lime construction research in the UK, the same problem is occurring in Ireland resulting in some unsuccessful builds.
    I would like to clarify that the binder used at the workshop was not hydrated lime, sand, hemp and water. As far as I am aware this is not a mix that has been used for hemp lime construction in Australia or elsewhere. The binder used at the workshop was developed and tested at UNSW. I’m not sure if anyone has built a house successfully using the recipe you are promoting, however if that is the case, then it ‘s important to quote the authority who has proven the mix rather than confusing the information.

      • Hi Owen,
        Unfortunately there’s an error in the Owner Builder article and it was not sent to me to proofread. Hopefully you’ve found plenty of information to get more of an understanding. Sorry for the confusion.

        You would certainly be protecting your hemp from decomposing using hydrated lime and if you could put enough lime or other natural clay render over the surface over say hessian bags filled with hemp, hydrated lime, sand and water and you got enough set in the bags and could then leave it for a longtime to get some stability, you would have a building.

        if you are not after a dead straight, sharp edged building requiring solid formply, building between forms can be inexpensive. The material does not slump so a variety of lighter materials can be used for forms.
        regards
        Klara

  12. Pingback: Hemp bricks are harder than concrete for homes and buildings « Geopolymer House Blog

  13. Pingback: Hemp Crete blocks used to build Annex.

  14. So are you saying you plan to fill bags with hempcrete and use them just like you have all the other bags? Would it be more expensive do you think and have you tried it yet?

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