Getting the basics right - The Hempcrete Topic: Designing and Building with Hemp-lime - page 106

Faulty materials
This is a much rarer cause of problems, and one that could of course occur with any build-
ing material, but in practice it should hardly never happen, as long as materials are bought
from a reputable source.
Faulty binder
A faulty binder might either not take a sufficiently strong initial set (so the wall is unable
to support its own weight, and slumps downwards) or not cure properly over time, leav-
ing a wall that is structurally unsound. Both of these problems are virtually unheard of in
hempcrete construction except in the case of materials that have not been properly tested,
such as the two described as follows.
This is the reason that we don't recommend making your own hempcrete binder according
to one of the various recipes that have been made available online or in topics (see Chapter
6 ) . If you really have a desire to experiment with making your own binder, then treat it as
just that - an experiment. Never use untested materials to construct a real building.
Worryingly, however, we at Hemp-LimeConstruct have recently seen two examples of
complete material failure: one concerning a material sold for use as a hempcrete binder by
a UK company and one concerning a complete ready-mixed 'hemp-limecrete' sold by an
Irish company to a UK self-builder. In neither case did the material manufacturer-supplier
accept any liability for the failure of the material, and in fact the Irish company refused to
do a site visit or to accept recorded correspondence on the subject sent by the UK client.
In the first example, the desire (for reasons of sustainability) to develop a hempcrete binder
that contained UK lime and no Portland cement led to a new product being sold to UK
hempcrete builders for use in buildings as a kind of 'in-practice test', with the consent
of clients. Unfortunately, the binder material in question was completely inappropriate for
hempcrete and failed even to hold its own weight, despite being built up to height quite
slowly. After a week or two, gaps appeared at the top of the wall where the material had
slumped down, and after a further two weeks a bright multicoloured mould appeared all
over the surface (see photos below and overleaf) and in the voids left where the material
had slumped. The wall had to be removed at the expense of the builder and client, since
the manufacturer refused to accept any liability for the material.