Hemp in construction - The Hempcrete Topic: Designing and Building with Hemp-lime - page 24

Details of hemp shiv suppliers in the UK can be found in the Resources section at the back
of this topic.
Cast-in-situ hempcrete
Cast-in-situ hempcrete refers to mixing hempcrete on-site and casting it into moulds con-
structed from shuttering, or formwork, to form the walls, floor or roof in the exact position
that they will remain within a building. The shuttering may be temporary or permanent.
Because hempcrete is a non-load-bearing material, it is always cast around a structural
frame, which provides the main load-bearing element of the building. This is usually, but
not always, built of timber. This applies whether it is being used in a new build or a res-
toration context. In new builds the usual method is to construct a simple studwork frame
from softwood, and bury this within the centre of the hempcrete wall, but alterations can
be made to the frame to accommodate different design details, both of the wall itself and
of internal and external finishes.
Mixing the hemp shiv and binder together with water can be done with a variety of types
of mechanical mixer, depending on the quantity needed, the speed at which it is required,
the method of application and access to the site.
The freshly mixed hempcrete is either placed (rather than 'poured', since it isn't a liquid
consistency), or sprayed into the void created by the shuttering. It is left for a short time to
take an initial set (i.e. set hard enough to bear its own weight), after which the shuttering,
if it is temporary, is removed and the hempcrete is allowed to dry out gradually over the
next few weeks, until it is dry enough for finishes to be applied.