Frequently Asked Questions
Q1. What are the materials used to make Hempcrete?
A. We grow our own Industrial Hemp for building, mixed with our own lime binder called ”iBinder” which has all the hydrated and hydraulic limes included. Or for international projects we supply the ”iPozz” and you source and add the hydrated lime.
Q2. How is Hempcrete mixed?
A. You can download our mixing instructions here.
Q3. How is Hempcrete placed and compacted?
A. Either with temporary forms (GeoPanels) on either side of the structural frame, screwed to the frame at the thickness you are casting or with permanent interior lining board and temporary exterior shuttering (boxing). Read more here.... Tamping the exterior edge of the Hemp/Lime mix will add compaction to the exterior edge of the wall.
Q4. How long do you leave the temporary shutters on?
A. As soon as we have cast a section of wall we can immediately move the shutters to a new section of wall. Typically we finish casting for the day and move the shutters next morning.
Q5. How high can we cast at a time?
A. Typically we will cast in 2’ (600mm) lifts but you can do as little or as much as you like, depending on manpower.
Q6. Do you need to do any testing of materials before starting the job?
A. NO - you will easily find a rhythm of mixing, casting and tamping with the work crew you have on site and ratios of hemp to binder to water are standard for all applications.
Q7. Can we build foundations with hemp or do we use concrete?
A. Hempcrete cannot be used below ground for foundations. You will see misinformation on the internet about using Hemp/Lime for foundations but that is not accurate. Cellulose exposed to below ground dampness for extended periods will deteriorate, like any plant material, even wrapped in lime.
Q8. How long do we leave the Hemp/Lime wall to dry before plastering?
A. Depending on the time of year typically we leave the walls to dry out for 4-6 weeks before plastering. At around 15% moisture content you will not get any leaching of the lignin’s from the cellulose - too wet and lignin’s may leach out thru the lime plaster.
Q. What precautions do we need to observe when using Hemp/Lime?
A. Lime is caustic so it’s a good idea to wear gloves when working with Hempcrete. Goggles and dust masks make for a more pleasant experience too.
Q9. Is there any waste when working with Hemp/Lime?
A. There is always spillage when casting Hempcrete but we pick it up and re-use it in subsequent mixes so no waste.
Q10. What happens to the hemp walls if it rains?
A. Hempcrete will take on water if rain is beating against it. Depending on climate and time of year you may consider protecting the casting areas with tarp’s. That way you can keep working in inclement weather. But, we don’t recommend casting Hempcrete walls below -5% Celsius - anyway that’s way too cold to be working outdoors. We did that once and never again!
Q11. What finishes can we apply over HempCrete?
A. Hempcrete provides its own substrate for application of lime plasters (stucco) directly without need for metal lathing. Or you may wish to use brick, wood or metal facing for aesthetics. Other than wood facings we install a breather baton so the Hempcrete can maintain air flow because metal is not permeable.
Q12. Can we use Hempcrete for bathroom walls?
A. Yes, you can use Hempcrete in a bathroom and finish with lime or clay plasters that will breathe in and regulate moisture. In Europe people have been using lime materials for ages in bathrooms without the need for extraction fans.
Q13. What finish can we give the flooring if done with hempCrete?
A. Hempcrete can be used to insulate floors over which you can apply a sub-floor and then whatever flooring material you wish. We prefer to leave a 1" air gap between the floor joists and the subfloor to allow Hempcrete to breathe, thereby giving the best insulation value.
Q14. Can the roof be done with hemp/lime?
A. Yes, the roof can be done with Hempcrete but remember, as above, there needs to be a 1" breathable air space between the top side of the Hempcrete and the underside of the roof sheeting material, presumably plywood, or Hemp Board, also available thru Hemp technologies.
Q15. Does Hempcrete require expansion joints?
A. NO expansion joints are required using Hempcrete materials, unlike cement. Even when finishing Hempcrete with lime stuccos there is no need for expansion joints as lime is very flexible and will heal itself after only a couple of months. New buildings are prone to settling and cement finishes will crack as they are brittle whereas lime will crack but reshape itself because of its crystalline shape.
Q16. Are there any special requirements when casting Hempcrete?
A. There are no special trades required to install Hempcrete walls, floors or roofs, making this material even more suited for non-skilled labor. Hemp Technologies provides initial training to anyone purchasing materials to get them started and learn a few technical issues associated with using these materials, such as forming, mixing, casting, tamping and finishing. Our charge for this certification fee is $1 per square foot of the project being built (USA and New Zealand only) and is a one-time fee to cover our expenses incurred to share this knowledge.
Q17. How big an area can we cast at once?
A. Casting into double sided temporary shutters, a 4-5 man crew can form and cast an average 200 cubic feet per day (7 cubic meters).
Casting into single-sided temporary shutters, a 3-4 man crew can cast an average 200 cubic feet per day (1 less man). This means a permanent interior wall liner using MgO is used instead of gypsum drywall.
Casting into double sided permanent shuttering, a 2-3 man crew can cast 400 cubic feet per day (6-800 square feet). Less men and more infill completed; definitely the best method.
Q18. When mixing Hempcrete do you need to vibrate it like concrete?
A. NO. When mixing Hempcrete and casting you do not need to vibrate like concrete. There is no "slump" in Hempcrete as we limit the amount of water used to hydrate the lime binder. Typical mix is 4:1:1 being hemp, lime, water respectively, for a tamped mix.
Q19. How about framing: any special conditions?
A. Hempcrete is regarded as a non-structural, monolithic infill material, cast around the structural timber or steel frame of the structure. Typical framing standards in North America require 2x4's at 16" on center however with support from structural engineers, we have reduced the amount of timber framing by 30% by framing at 24" on center using 2x4's, both on single and double story structures. This is because Hempcrete will harden and in fact help to brace the structural members.
Q20. What is the mixing time of 1 cubic meter?
A. Most people use a regular mortar mixer (horizontal) in which you can mix 100 liters (25 lbs or 11.5 kg) of hemp with the required ratios of Lime binder and water. The water goes in first, then the binder, mixed for 2 minutes, then hemp is added and mixed for another 1-2 minutes until all the shiv (hurds) are covered with the lime binder. By running 2 mixers you will double your output without need for special equipment.
Q21. What is the cost difference between a 6" wall to the 12" wall?
A. Depending on climate zone you are wishing to build in will determine the thickness of wall required to achieve adequate insulation. The most common thickness is 12" (300mm) based on temporary forms being used both sides of the cast wall. However, if using permanent forms tamping is eliminated from the equation and a thinner wall will achieve the same R-Value.
Q22. Do you have a cost per square foot of wall?
A. There is a typical 300mm wall costing download available on our website (click here).
Q23. Does that cost include labor?
A. Labor costs ~US$6/square foot installation. Labor rates do vary by country, State and Region.
Q24. How did the idea of using hemp for building come about?
A. Building materials have been morphing for some years but many companies simply ”green wash” existing materials to make them look more agreeable to consumers. Industrial Hemp has been on our planet for thousands of years and used in many ancient structures together with limes long before we had conventional cement. We have adopted a carbohydrate approach to building healthy homes without the need for petrochemical where possible.
Q25. What was the process while starting Hemp Technologies?
A. We traveled extensively throughout Europe visiting with people who had been building with Hemp/Lime for many years to gain the knowledge necessary to bring these materials to other countries, including USA, where construction waste accounts for almost 50% of land fills and job site waste 19%.
Q26. How is hemp more beneficial in building compared to other materials?
A. Carbohydrate based building materials are healthier and less damaging to humans. Toxic petrochemical materials are responsible for many illnesses and increased medical bills. Hempcrete is breathable and is completely non-toxic due to all natural materials. Plus, Hemp/Lime protects the structural integrity of a home and therefore will last considerably longer than conventional construction.
Q27. Are hemp building materials cost effective?
A. Hemp/Lime materials are comparable in cost to traditional brick and block construction.
Q28. Are hemp building materials safe/healthy?
A. There is documented evidence that Hemp/Lime has contributed to more than 50% reduction in sick leave and absenteeism in Europe where they have been building with Hempcrete for +/- 30 years now.
Q29. How does hemp help cut down on energy use?
A. Because Hempcrete is super insulating the need for additional mechanical heating/cooling is reduced. For example a typical home will have 1 ton HVAC per 500 square feet. Using Hemp/Lime for insulation will reduce that requirement to 1 ton per 1500 square feet (60%) That equates to another cost saving when building with Hemp/Lime.
Q30. How did your team/company come together?
A. Hemp advocates with special skill sets have gravitated to Hemp Technologies thru the education we provide online for hemp. Over time certain people have naturally evolved into working with us to promote hemp building, as well as other hemp related products.
Q31. What are the legal issues that come into play? Are there any?
A. We have no legal issues around building anywhere in USA/Canada, or any other country for that matter. The issue in USA is not being able to grow Hemp. As one CNN reporter put it. ”its like we can buy the bread but we can’t grow the wheat”. Until the Federal Government relaxes their stance on Industrial Hemp and allows farmers to grow this wonderful life giving plant in USA costs will remain high in comparison to other petrochemical based building materials.
Q32. Animal bedding: how does hemp assist in this area?
A. Hemp is a premium animal bedding and 80% of all hurd production in Europe goes into pet bedding currently. Hemp absorbs 4 x more waste than other bedding materials yet decomposes 2x faster after use. This makes hemp very good for use as a fertiliser after being used for bedding. Yes, it is more expensive than other bedding materials but reduced labor costs over time make Hemp more affordable over all, and better for your pets.
Q33. What are Hemp Technologies' future plans? Can we hope to see hemp building sweep the United States?
A. We are building one house at a time and helping to educate others on the use of these natural, renewable building materials. Like any new materials introduced into the market, more demand will reduce costs, making it more and more affordable to build with these materials as time goes on. Also, localising the source for binder materials will help more people afford to build with Hemp/Lime.
We are in a constant state of evolving the company, to include pre-fab, pre-dried building solutions using hemp, reducing job-site waste and the time to build.
Q34. What would it take to have hemp building in more states?
A. We provide training to builders, home owners, architects, engineers, DIY’s and other professionals to use Hemp/Lime for building. In so doing more and more people are becoming familiar and comfortable with these materials.
Q35. Are the materials similar to concrete, planks, etc.?
A. Hemp/Lime is way lighter than cement and thus requires lighter foundations. We don’t yet have planks developed for use in North America.
Q36. How popular is hemp mulch for gardening and compost?
A. Growing in popularity, Hemp is a fabulous mulch, absorbing 4 x it weight in moisture and retaining it longer than other mulching materials. Your plants will love it.
Q37. How does one study or get into careers/businesses involving hemp?
A. Start by reading thru all the information available free on our website. From farming to processing to uses of Hemp you can get a solid understanding of Industrial Hemp and its uses from us and other websites dedicated to promoting the value of Hemp, the miracle plant. We also provide a global map of hemp builders so it’s not hard to find someone close to you to help build your hemp home. We help by supplying the materials at wholesale pricing that you will not find anywhere else.
Q38. How long will it take until hemp homes/buildings are affordable for everyone?
A. Hemp homes are affordable NOW, starting at US$130/square foot, plus your land and ground works costs. Banks are recognising more and more that building with hemp/lime is very, very energy efficient and have given mortgages to people based on the reduced energy costs. PLUS, insurance companies give up to 60% discount on fire insurance because Hempcrete is non-combustable!!! Get started today by contacting us here. We have associates all over the globe who will assist in making your healthy home a reality.