Frequently asked questions
No – you don’t need to put any cement or concrete in a hempcrete wall. Sometimes a
builder may choose to put a very small percentage in (4% ) but it is not necessary and
beautiful hempcrete homes exist all over the world that don’t have cement in their mix.
Hemp Hurd (the inner stalk of the hemp plant, sometimes called shiv but here in NZ
mostly called hurd) plus a lime based binder + water
This will depend on the actual yield of hurd that you get from your crop – but as a
starting ballpark figure, 3 acres of hemp can yield enough hurd to build a 150sqm house.
At the moment it is roughly equivalent to slightly above average. (We quote its the same
as a brick and cement block house) So it’s not outrageously cheap or expensive and of
course the actual cost of a home per sq meter will depend on the finishings in bathrooms
and kitchens.
But there are ways to build with hemp that can reduce the cost:
1. Grow your own hurd.
2. Get whanau to help with the labour (hempcrete wall building isn’t hard, toxic, or
heavy work, just repetitive and involves a lot of hours.)
3. Rather than start your home from scratch, you could remove existing walls, leave
the roof and frame and ‘retro fit’ by building new walls of hempcrete with the existing
frame/roof.
Yes!! All the existing hempcrete homes in NZ have achieved code of compliance (ie –
signed off and able to get insurance).
The NZ building code is a performance based one, which means that walling can be made
from anything (and called an ‘alternative’ solution) as long as it can be proven to be able to
perform and meet building code specifications.
So practically what happens is that hempcrete project is inspected as usual by the local
council building inspector. The builder provides that inspector with the documentation /
information about hempcrete’s performance, which assists the inspector to assess that the
hempcrete will be able to meet the code specs.
HBANZ can potentially assist with this.
However, all the home owner builders that have
built hempcrete homes so far in NZ have (usually in conjunction with their home designer) been able to provide the required hempcrete spec/performance documentation to their inspector, using existing data from either UK or Australian sources.
1. Attend a hempcrete building workshop – HBANZ will be hosting them soon. Kohu hemp
https://kohuhemp.nz are also running hemp building 101 and 102 workshops.
2. Buy one of the books listed in our resources section. Devour!!
3. Contact Erkhart Construction (Wanaka based super friendly builder who could talk
through possible options)
Hemp houses are built with industrial hemp which has been legal to grow in NZ since
2001.
Industrial hemp has to be tested and conform to having less than 0.3% THC in it.
So yes – industrial hemp and the two commodities products processed from its stalk (hurd and bast fibre) can be used to create virtually ANYTHING, and are legal.
Referred to as the ‘hand-placed method’.
Firstly – the frame and roof are built. The frame of the hempcrete house is the load bearing
element. (N.B.: Hempcrete itself is not generally a load bearing product. However there
are scientific innovations and research currently happening which will mean that soon we
WILL have a load bearing version of hempcrete).
Once the frame and roof are up, the builder fixes temporary form work (or shuttering) to
the frame.
The hempcrete is made up in a pan mixer: Hemp Hurd + lime binder + water. It is used to
fill in the space between the formwork and sets in a few hours. Once set, the formwork is
take off and moved to create the next level or area.
A hempcrete wall will need 6 – 8 weeks to completely dry out. It can then be rendered with
lime on the outside. It can also be plastered on the inside or left ‘raw’ – or a combination of
the two.
The design of a hempcrete house should include a reasonable overhang of its eaves, to
contribute to its watertightness.
Hempcrete can be made into pre fabricated panels off site and dried, then transported
to the site… Hempcrete can be sprayed (like concrete)…. And it can be made into blocks.
Yes! Hempcrete is not a load bearing material, but rather it is an infill walling product. So
your house designer would use an engineer to ensure that the frame and foundations will
work. Hempcrete overall is usually lighter than most other walling systems (which involve
cladding / insulation/ internal linings).
As with any house, a hemp house’s appearance will be determined by its design and
its external finishing product or renew coating.
Most of the hemp houses we have seen look like traditional material houses – ie they have
a modern or contemporary look. (Check out our gallery here).
The quality of the exterior render will create either a sharp ‘modern’ look or a more rustic
less uniformed look. The choice is yours!
- CO2 sequestration
- Negative carbon footprint
- High thermal comfort performance
- Prevents mould / dry rot
- 50% – 70% energy savings
- Breathable walls
- Healthy living environment
- Fire Proof
Termite resistant - Design flexibility
- Inherently Airtight
- Great acoustic performance
- Natural Substrates for Plasters and Renders
- Zero Landfill during / after build