Placing hempcrete - The Hempcrete Topic: Designing and Building with Hemp-lime - page 347

The process of placing hempcrete is a deceptively simple one: while it is true that the
basic method is straightforward, it does require some skill and an understanding of
the important qualities of the finished cast hempcrete material. Moreover, it de-
mands knowledge of the effects that differences in placing technique can have on
these key qualities.
Before we look at the method itself, it is worth briefly discussing the principles involved,
as a good understanding of these underpins successful technique.
Basic principles
When placing hempcrete, the aim should be:
to fill the whole of each shuttered void evenly and consistently with hempcrete, with no
gaps, and achieve a good proximity of the placed hempcrete to the frame timbers
to achieve a consistent, low-density cast material: strong enough to hold its own shape,
but trapping the maximum amount of air inside it to provide as much insulation as pos-
sible.
In order to achieve a consistent, low-density material it is important to avoid over-com-
pacting . At Hemp-LimeConstruct we very rarely use a 'tamping stick' (or any other tool)
to compact the hempcrete in the void, as we have found that this encourages people to
over-compact it. This is because if your hand is not in contact with the hempcrete itself,
you cannot feel how much it has been compacted.
There are two exceptions to this rule. A stick can be used if needed to extend your reach
into an area of the void that is difficult or too far away to reach by hand. In this situation
the stick should be used, as far as is possible, in a way that replicates the motion of your
gloved hand. A stick is also used when tamping is required - which is usually in areas
of thin coverage over frame timbers, where more compaction is needed to give increased
structural integrity, at the cost of a little loss of insulation. A short length of roofing batten
is generally used for this purpose, but occasionally a plate is screwed on to the bottom to
create a tamping stick with a slightly wider area.