Civil Engineering Reference
In-Depth Information
Despite the 'open' matrix structure created by the particles of binder-coated hemp with-
in the wall, it sets very hard and strong when fully dry, and is perfectly strong enough to
fix into for light-duty fixings, for example for pictures or small mirrors, using wall plugs
as you would with a conventional masonry wall.
For more heavy-duty fixings, such as wall-mounted radiators, guttering downpipes and
wall-hung cupboards, a hempcrete wall may not have sufficient density to support the
weight hanging from it. There are two solutions: the first is to use wooden rails cast
flush with, or just behind, the surface of the wall. Including a horizontal wooden rail
in the frame design at, say, 900mm and 1800mm enables a strong fix anywhere in
the room at dado and picture-rail heights. Clearly this needs to be integrated into the
design at the wall build-up stage; if this is not done, and strong fixings are required
once the hempcrete has set, the solution is to use wooden wedges hammered into the
dried wall to take a fixing. These are set so that the wide end sits flush with the wall
surface and screws can be fixed straight into the wedge, and have the advantage that
they can be set in at the exact place where the fixing is required. You may have seen
this method used in Victorian houses as a way of providing a fixing for skirting boards.
It is particularly effective with hempcrete, since the set hempcrete has elasticity and
'bends' under excessive pressure rather than breaking. This means that the hempcrete
around the wedge gets pushed outwards, and becomes denser in the immediate area
surrounding the wedge, thus holding it more firmly.
As an alternative to fixings, remember that, since hempcrete is a cast material, it is
relatively simple to create attractive and functional recessed alcoves and shelving by
making a mould to use as part of the shuttering and casting the hempcrete around it.
With this in mind, take the time to plan your use of each room carefully before you start
work.
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