Restoration and retrofit - The Hempcrete Topic: Designing and Building with Hemp-lime - page 467

centrally down the inside of the frame to provide a fixing for shuttering screws, which
can also be fixed into the vertical studs if necessary (see Figure 15(a) overleaf).
If desired, a piece of natural-fibre quilt insulation can be fixed between the battens and
the inside of the frame to improve airtightness at the edges of each hempcrete panel.
All permanent fixings should be stainless steel or (in the case of nails) hot-dip galvan-
ized.
Board out the whole of one side of the panel in advance and then gradually build up
shuttering across the other side, filling with hempcrete carefully to ensure all areas
within the panel are filled evenly.
Because the infill panels are generally narrower than for new-build walls, smaller lifts
(200-400mm, depending on the frame) are usually required to ensure easy access when
placing the hempcrete.
If appropriate to the character of the building, the shuttering can be spaced out from the
frame slightly using battens as packing, and the hempcrete shaped back afterwards to
form a soft 'pillowing out' of the infill either side of the frame (see below). This
provides an aesthetically pleasing effect while adding a little more insulation than is al-
lowed by the width of the frame alone.
When the top of the panel is reached, the shuttering board is moved up in smaller and
smaller lifts (overlapping the hempcrete below), until a small space under the top frame
timber is left. This is filled by pushing hempcrete in from the side, and it is best to do
this with freshly mixed hempcrete straight from the mixer, as you are relying on the lat-
eral adhesion of the most recent section of hempcrete to the previous one in order to
keep it in the panel.
When the shuttering has been removed, wait for the hempcrete to set sufficiently for
any shaping work to be done using a nail float or multi-tool. Even if the panels are not
being 'pillowed out', it is normal to cut the edges of the panel in behind the timber in
this way, to about 25-30mm (see Figure 15(b) ), so that when finishes are applied they
are closed in thoroughly to the timber, with a 'shadow line' effect (see Figure 15(c) ) .
When the hempcrete has dried sufficiently, apply finishes as normal. Note that because
the panels are normally thinner than in a typical new-build hempcrete wall, the drying
period can be shorter.