Essential Hempcrete Construction launches Sustainable Building Essentials Series

by: Sara on 06/15/2016

Hot off the press! Essential Hempcrete Construction:The Complete Step-by-step Guide kicks off the launch of our exciting new Sustainable Building Essentials series.

Written by Chris Magwood, designer and builder of some of the most innovative and sustainable buildings in North America, this book will cover a complete step-by-step guide to using hempcrete.

Made from the inner stem of the hemp plant mixed with a lime-based binder, hempcrete is a very strong, lightweight, and breathable alternative to manufactured insulations. Essential Hempcrete Construction is a fully illustrated practical guide to this affordable, renewable method, from procurement to finishing.

Going well beyond the scope of many natural building books, this indispensable manual includes a complete introduction to hempcrete, packed with all the information you need to determine whether it's the right choice for your project. It covers:

  • Material specifications, testing and building code references, and climate data
  • Detail drawings for design reference
  • Tool lists and complete step-by-step instructions for mixing and placing hempcrete
  • Finishing and maintenance techniques
  • Budgeting and labor estimates
  • Additional resources.

Featured below is an article on a hempcrete workshop hosted at Chris Magwood’s Endeavour Centre for natural building.

On April 9, a workshop at Endeavour brought participants together to explore hempcrete insulation materials.

The workshop looked at well-used options for these materials, but also explored some interesting new approaches.

Endeavour has continued to develop the use of homemade hydraulic lime binders as a means to eliminate carbon-heavy cement from our building materials and to create locally-sourced binders for cement replacement. At this point, our homemade hydraulic lime binder is well-tested and we feel it works as well as any of the imported (European) hempcrete binders, at a fraction of the cost and with locally-sourced ingredients.

Hempcrete Mix

hemp 1

Weight ratios are converted to bucket measurements: 1/2 bucket of lime, 1/2 bucket of metakaolin, 4 buckets of hemp hurd

Our hempcrete binder is composed of 50% hydrated lime (most easily accessible to us isGraymont’s Ivory Finish Lime) and 50% Metapor metakaolin from Poraver (created as a by-product of the company’s expanded glass bead production).

We mix our hempcrete at a ratio of 1 part chopped hemp hurd by weight, with 1.5 parts of the binder by weight. After translating these weights to volume measurements, it was 4 buckets or hemp hurd going into the mixer with 1 bucket of binder (1/2 lime, 1/2 metakaolin).

The hemp hurd goes into the mortar mixer first and then we sprinkle in the binder and allow it dry mix until the hurd is well coated with binder powder.

Water is then misted (not sprayed) into the mixer until the mix is just moist enough that if we pack it like a snowball in our gloved hands it keeps its shape

hemp 2

A horizontal shaft mortar mixer is used to dry-mix the lime binder and the hemp before water is misted into the mix

, but is still fairly fragile (ie, can be broken with a bit of a squeeze). It is important to not over-wet the hempcrete, as this will greatly extend the drying time once the hempcrete has been packed into a wall. If too much water is added, the mix can’t be recovered by adding more dry ingredients as the hemp hurd will quickly absorb excess water and there won’t be any free water for the new dry ingredients. So, add water carefully and gradually!


hemp 3

When packed like a snowball, the hempcrete should just hang together

Hempcrete is placed into formwork on a frame wall, using light hand-pressure to compact the mix just enough to ensure that the binder will stick all the individual pieces of hemp together.

Hempcrete is placed into forms and lightly pressed into place. The forms are leap-frogged up the wall.

Our workshop crew was able to mix and place enough hempcrete to fill a 4-1/4 inch deep wall cavity that was 4-feet wide and 13-feet high in just under 3 hours! That’s over 6 cubic feet of material per hour!

Hempcrete Recycling

We have long touted the no-waste benefits of hempcrete. We’ve speculated that even when the insulation is being removed from a building during

hemp 4

Hempcrete is placed into forms and lightly pressed into place. The forms are leap-frogged up the wall.

renovations or demolition, that the hempcrete can be broken up and recycled into a new mix with new binder added. We put that theory to the test at the workshop, as we demolished one of our small sample walls and added the broken up hempcrete into our new mixes at a ratio of 3 parts new hemp to 1 part recycled hempcrete. The resulting mixes were impossible to distinguish from the all-new mixes, and confirmed that hempcrete can easily be re-used!

hemp 6

Hempcrete that had already been mixed into a wall was broken up and added into a new mix… Fully recyclable!



For the complete hempcrete workshop blog continue reading here


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