Civil Engineering Reference
In-Depth Information
Electricity
To save time, money and mess it is better for the electrician to come in as soon as the struc-
tural frame is complete, in order to run all cables within the wall structure. Cables need to
be run inside plastic or metal conduit. This has two functions:
it gives a little extra protection to the cables (against badly aimed drilling in the fin-
ished wall and against accidental damage on-site before the hempcrete is cast).
It allows air to flow around the cable, which minimizes the risk of overheating caused
by the cables (which get warm as the electric current flows through them) being too
closely surrounded by the insulating hempcrete.
Conduit containing electricity cable is easily run along the frame timbers and, where ne-
cessary, can be fixed securely in place with conduit mounting clips.
Where a socket or switch is to be mounted on a hempcrete wall, the back box can be
screwed directly to the frame, or to special extensions to the frame. It should be positioned
so that the front of the box sits exactly level with where the face of the wall will be. The
temporary shuttering can then run along the front of the box with no cutting of boards re-
quired, and the hempcrete can be cast around the back and sides of the box, with the front
left visible in the surface of the wall.
If permanent shuttering is used internally, plastic dry lining boxes can be used. This re-
duces the need for extra frame timbers to support electrical installations.
Although it is sensible for electrical installations to be fitted before the hempcrete is cast,
sometimes it is necessary for them to be retrofitted. In this case, channels can be chased out
of the surface of the wall, once it has set, using a powered cutting tool such as a multi-tool
or disc cutter. Electric cable in conduit is inserted, and held in place with clips hammered
into the hempcrete. A hemp-lime-sand mix can be made up and used to fill in the channel.
When refilling these channels, it may be useful to use Prompt Natural Cement as a binder,
since it sets very quickly.
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