The structural frame - The Hempcrete Topic: Designing and Building with Hemp-lime - page 256

Smaller buildings
Buildings of up to three storeys can be constructed using a simple studwork frame, and this
is the usual approach taken for any hempcrete building up to the size of a large house. The
discussion in the rest of this chapter relates to the timber frame for a hempcrete building on
this scale. The frame can usually be constructed from untreated European softwood, which
is a natural and sustainable resource.
For very simple builds, such as small extensions or simple one- or two-storey buildings,
those who have the necessary skills may wish to design their own frame. The stud frame
required for these types of building is simple enough that building control inspectors will
be familiar with its structural limits. Whether you are undertaking the design of the struc-
tural frame yourself or whether it is being done by an experienced engineer, we advise that
the standards of construction set out by the Timber Research and Development Association
(TRADA) 1 are followed.
The standard simple stud frame design for hempcrete walls consists of the following basic
elements:
A sole plate , which sits on top of the damp-proof course (DPC), usually on top of the
plinth.
Structural studs extending vertically from the sole plate. Normally designed to sit in
the centre of the cast hempcrete, these provide a key for the hempcrete to resist lateral
movement, as well as providing the load-bearing strength necessary to support the roof
and upper floors.
A wall plate , which runs around the top of the studs, to which the roof structure is at-
tached.
Diagonal timbers , which provide racking strength as necessary.
Where there are two or more storeys, it is usual to include an intermediate plate for
upper floor joists to bear on, with further studs extending from this plate to support the
wall plate at eaves level.
All frame fixings that are exposed, however slightly, to the hempcrete should be of stain-
less steel or painted with a protective coating once fixed, so that they resist corrosion by
the lime in the hempcrete.
Increasingly, engineered timber joists are incorporated into roofs and floors to cut down on
the section size of timbers used in bridging large spans. They contain less timber, which