Restoration and retrofit - The Hempcrete Topic: Designing and Building with Hemp-lime - page 466

Bespoke solutions are likely to be needed to meet the requirements of the particular
building in question.
Hempcrete infill panels to an existing timber frame
Infill panels in a heritage building tend to be much narrower than new-build hempcrete
walls, so special care should be taken to create as low density a hempcrete as can meet the
requirements for strength and integrity of the material, as the priority should be to create
as much insulation as possible within the available space.
The following is our 'standard' method for constructing hempcrete infill panels to an exist-
ing frame. This method is adapted constantly to the particular requirements of the building
we are working on, and, as already noted, it is more important to achieve the principles
outlined above within the constraints of the building and planning conditions than to stick
rigidly to the method described here.
Consider carefully any panels that contain original and/or historically important material,
such as wattle and daub. If this is intact, the priority should be to preserve it, but sometimes
even damaged panels with quite extensive loss of the original material can be preserved,
with hempcrete added to replace the missing wattle and daub. The viability of preserving
partially damaged panels should be assessed on a panel-by-panel basis (in the case of listed
buildings this should be done in close liaison with the conservation officer). The method
set out below is likely to vary slightly from building to building.
Wear appropriate PPE when mixing and placing hempcrete, and ensure safe working
practices are followed (see Chapter 9 ) .
Clean out all material from previous 'repairs': usually this consists of metal lath and
cement, but we have also come across attempts at insulation panels using a softwood
structure supporting polystyrene boards.
Construct a row of reinforcing vertical studs centrally within the frame at intervals,
specified by a suitably qualified person, sufficient to provide good lateral resistance to
the hempcrete panel. These studs can be sawn battens, or coppiced roundwood (usually
hazel or ash). They are fixed top and bottom into hardwood battens running left to right
centrally within the frame. Their section size should be sufficient to provide the neces-
sary reinforcing strength while allowing them to sit centrally within the frame with a
good covering of hempcrete over them.
If screws to hold temporary shuttering cannot be fixed directly into the outside (visible)
faces of the timber frame for aesthetic reasons, separate hardwood battens can be fixed