Civil Engineering Reference
In-Depth Information
Hempcrete is not a load-bearing material, so it is always used in conjunction with a
structural frame to take the load of the roof and upper floors safely down to the
foundation. The hempcrete is typically cast around the frame, and provides racking
strength to it. For buildings of up to three storeys, the frame will generally be made
from softwood timber. Hempcrete is perfect for casting around timber frames as it
has a certain level of natural elasticity and is able to cope with the slight movements
that are normal in timber-frame structures.
Various types of structural frame can be used with hempcrete, and the frame is usually de-
signed by, or at least its structural members specified by, a structural engineer and is sub-
ject to close scrutiny from building control. In larger buildings, where the frame is likely to
be glulam (glued laminated timber), steel or concrete (see overleaf), a softwood sub-frame
is still required to support the hempcrete. You will need to provide your engineer with a
set of drawings containing at least floor plans, elevations and your intended wall section,
showing where ideally you would like the structural frame to be positioned. Your engineer
will also need to know what type of roof covering you are going to have and the position
of any heavy mechanical or electrical equipment intended for the roof (e.g. solar panels).
He or she will also need details of the density of the hempcrete you are using, and will
need to understand the implications of casting hempcrete around a timber frame in terms
of reducing horizontal frame members. From this information the engineer will be able to
specify the size of structural members within the frame and provide a set of calculations to
satisfy the appropriate Building Regulations requirement.
Your engineer may not have come across hempcrete before, so if you want to simplify the
frame, to reduce costs and make placing the hempcrete easier, you may have to inform him
or her about its characteristics. The frame design has the potential to make the process of
placing the hempcrete very easy or very difficult.
Large buildings
A very large hempcrete building usually has a substantial structural frame, especially
where it has either a very heavy roof or is supporting four or more storeys. Large frames
can either sit within the hempcrete wall or be set away from the wall inside the building.
It is beyond the scope of this topic to discuss the design of massive structural frames in
detail, and those who are constructing such buildings will have engineers to design a frame
with the suitable structural capabilities. For engineers seeking to adapt such frames to be
suitable for hempcrete, the principles outlined below can be followed.
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