The hempcrete wall: an overview - The Hempcrete Topic: Designing and Building with Hemp-lime - page 211

ity of hempcrete buildings in the UK) where this detail has been used with no detrimental
effects reported.
Untreated softwood and glulam beam making up the frame for a hempcrete wall.
If the idea of using untreated softwood in a structural application does not appeal to you,
or if it fails to satisfy local building control authorities, or for parts of the frame where
the timber is more exposed, three options exist. Clearly, treated softwood could be used
throughout, although this is not to be recommended owing to the toxic preservative and
pest-resistant chemicals with which it is impregnated, which could potentially cause health
problems through off-gassing into the home. A hardwood frame could be used, but would
be significantly more expensive; also, hardwood normally constitutes a less sustainable
material, as hardwood usually takes far longer to replenish through regrowth. A comprom-
ise option, then, would be to use locally sourced hardwood timber or damp-proof vapour-
permeable ('breather') membranes at parts of the frame that are more exposed or are in-
herently more vulnerable to moisture ingress. (See overleaf, and Chapters 13 and 18 . )
The wall is constructed around the timber frame by erecting temporary shuttering, which is
then filled with hempcrete. A permanent shuttering board made from a breathable plaster
carrier board (usually wood wool) can be used on one side of the wall, but on at least one
side the shuttering must be removed to let the hempcrete dry out after it has been cast.