On 20 June, Stephanie Crombie, ACAN Natural Materials Coordinator, attended a Hempcrete workshop in Walthamstow, North London. Here she reports her findings on why hempcrete is a viable material for construction.
What building material grows 4m in 4 months, can be intercropped with wheat, is mould, fire, and water resistant, and is arguably carbon negative?
Alex Sparrow (from UK Hempcrete) spent Monday this week showing that a simple mix of hemp shiv and lime binder really is the building material of the future. Effectively acting as monolithic insulation, hempcrete not only creates thermal, acoustic and hygroscopic comfort in our buildings, but is easy to build with and cost effective.
In the morning, we built a hempcrete wall with students of Waltham Forest College using a timber frame, with pre-cast hempcrete blocks to one side, cast hempcrete to the other, and lime plaster over the top. Compared to many of the external envelopes we specify, using a variety of membranes and waterproofing, this couldn’t be simpler. Getting your hands dirty is the best way to learn how we build our buildings. Hemp, which is essentially a processed plant stem, is a contractor’s dream – it is low toxicity, light and easy to work with.
In the afternoon we heard about a number of case studies that had chosen hempcrete for their thermal envelope, ranging from self-build garden rooms (such as, Kate Nicklin architect, self builder and director of Commonbond Architects) to multi-million-pound homes (such as, Jonathan Tuckey Associates) demonstrating that hemp really does have universal appeal.
Following the presentations, we gave a quick overview of what we’re up to at ACAN Natural Materials and how we’ve been promoting hemp in the past.
The one-day event was run by Max Dewdney from Studio Dera in tandem with the London Festival of Architecture. The agenda was based around their proposals for a new community centre and nursery at the Higham Hill Hub in Walthamstow, which proposes to use hempcrete in its construction and aims to be built by students from the local construction college. In this way, hempcrete is really closing the circle. It embodies environmental ethics, promotes local education, and acts for community benefit.
We have been using hempcrete in this country for over 20 years, but only recently has it taken a hold amongst architects and designers. The seminal project which put hempcrete on the map was Practice Architecture’s Flat House completed in 2020 – a rural R&D facility located at Margent farm using bioplastics, hemp and flax. Since then a number of projects have emerged using hemp, from leisure centres to breweries.
One of the main barriers to using hempcrete are the manufacturing requirements. We currently have the land to grow hemp, and we have the demand from the construction industry. What we are lacking is the infrastructure to process the hemp shiv – something Alex Sparrow told us he is currently working on. Watch this space as we expect to see a huge boom in the use of hemp over the coming years as these developments move forward.
Using more natural materials in our construction projects is vital if we are to tackle the climate and biodiversity crises we face. At ACAN, the Natural Materials working group is running a monthly series on a variety of Natural Materials available for use in construction. At the end of last year we held a 2 hour seminar on Hemp – this featured a number of expert speakers showcasing the capabilities of hemp and how it might be used in construction.
Other than hemp, we’ve also had events on earth, straw, lime, cork and more. If you’d like to join us for our events series, please subscribe to our channel. And if you’d like to get more involved in some of the other initiatives we’re working on please email us here: email@example.com.
by Stephanie Crombie, ACAN
Images: Max Dewdney