Civil Engineering Reference
In-Depth Information
resistance to both deflections and to
impact damage, particularly if they
have been laid to break joint.
For coefficients of linear thermal
and moisture expansion etc, see
Chapter 1.2.
Rising damp and condensation
Rising damp from a slab is unlikely
to occur provided the DPM is
satisfactory. Condensation is a
theoretical risk at the junction with
the external wall if the thermal
insulation is deficient, allowing a
thermal bridge.
Thermal properties
The acoustic curtain goes some way
to providing a reasonable standard of
heat insulation on each side of the
separating wall. There are no formal
requirements.
Figure 6.17
Steel framed separating walls under construction in 1996 in the Isle of Skye
Accommodation of services
Services should not be incorporated
in the separating wall, but where it is
essential that electrical sockets are
incorporated, they should not be
fitted back to back, and should be
backed by plasterboard of the correct
thickness.
Fire
Fire can spread between dwellings
having framed separating walls
where an effective fire separation has
not been achieved. In some
dwellings, the fire separation is
impaired where the fill between the
separating wall timber frames does
not abut the roof. Where the roof
space separating walls are lined with
plasterboard, gaps have been noted at
eaves and purlin positions. Boxed
eaves are particularly likely to
contain gaps which outflank the
separating wall. (See also
Roofs and
roofing
(24)
).
Dwellings built in industrialised
systems of construction have been
identified as possibly having poor
performance in fire situations. BISFs
and Hawthorne Leslies need careful
attention paying to fire-stopping at
the junctions of separating walls and
roofs. In the case of Steanes, large
voids have been found in the
separating walls. Steelwork fire
protection has been found missing in
a number of Arcals.
Cavity barriers will be needed at
various places, for example at the
junctions with other elements of
construction, such as floors (Figure
6.18) and external walls, for both fire
and noise reasons.
One hour's fire resistance should
be obtainable from a framed
Figure 6.18
The diagonal bracing in the separating wall
has prevented correct installation of the
cavity barrier at the intermediate floor
Main performance
requirements and defects
Strength and stability
Strength depends on the adequacy of
the studs and how well they are
nogged. Some separating wall leaves
may not be adequately tied together,
since ties might interfere with sound
insulation.
Dimensional stability, deflections
etc
There may be some shrinkage of the
timber studs as they dry down to their
in-service moisture content, which
could lead to cracking at the junction
with the ceilings and with the
external walls. It is unlikely to be
extensive. If the smaller section
timbers are dried down to 20%
moisture content at the time of
grading, the risk of subsequent
shrinkage is reduced.
Twin or triple sheets of
plasterboard will give sufficient
