Partitions - Walls, Windows and Doors - page 204

Extruded clay partition blocks
used to be made in the UK by a
number of firms to a British
Standard (216) , with grooves cast on
each of the larger faces to provide a
key for plaster, but other pattern
blocks may also be encountered
(Figure 7.3). Hollow cored or solid
gypsum blocks or panels for use in
partitions are not now common in the
UK but they are still made on a
considerable scale abroad and it is
possible some may be imported.

Cracking
develops as
floor moves
and bonding
holds
some
blocks to
external wall

Main performance
requirements and defects
Strength and stability
It may not be clear whether an
internal partition exists only to
subdivide space or to perform a
loadbearing or buttressing role or
both. An analysis of the structure
should reveal the function of a
partition. However, one should
always be wary of any fortuitous
contribution to overall strength, such
as where an essentially non-
loadbearing partition (ie having no
foundation) offers support to a floor
spanning over. If this sort of
arrangement has performed well
previously, and loads are not
expected to change, then maintaining
the status quo may be justified.
Conversely, situations will be found
where partitions impose excessive
loads on a suspended floor which
were not intended, perhaps resulting
in floor deflection and settlement of
the partition itself; this in turn could
disengage any head restraint
originally provided.
Masonry partitions may be
overstressed by superimposed loads
(eg water tanks in the roof). They
may be too thin in relation to their
height, not tied to other walls at ends
and not fixed to the floor or roof
structure above. It is bad practice to
position a rigid masonry partition on
a 'live' timber floor but such
arrangements are common, and often
result in cracking where partitions
abut rigid enclosing walls (Figure
7.4).
The relevant provisions of
BS 5628 lead generally to a
conservative design for single leaf
walls (218) .
In tests, single leaf clay brickwork
and concrete blockwork storey height
partition walls have been subjected to
static vertical loads representative of
those in cross-wall housing
construction up to three storeys high.
Simulated horizontal wind loading
was applied to the end of the wall
until failure occurred. Tests were
carried out on walls both with and
without a return at the loaded end and
the results compared. Walls with
returns

Abutments and corners
Partitions, especially non-
loadbearing and less than 100 mm
thick, cannot always be self-
supporting. Some masonry partitions
were provided with corner posts in
timber to provide the necessary
stability. In other cases, stability is
provided by full room height doorsets
pinned to ceilings, with the
blockwork held against horizontal
displacement essentially by the
architraves. Otherwise, returns are
necessary.

Figure 7.4
A rigid masonry partition built off a live
timber floor often results in cracking

Case study
Accuracy of blockwork partitions
The BRE Advisory Service was invited to
examine the blockwork partitions in a
bungalow and to comment on the standards
of accuracy achieved. Measurements were
made of the verticality of the walls in a
number of cases, and several were found to
be up to 30 mm out of plumb.
The British Standard Code of practice for
accuracy in building, BS 5606 (217) presents
the results of a survey of building accuracy
and shows how such data may be used in
specifying permissible deviations. From
these results, the verticality of blockwork
walls in 99.7% of cases measured (in
buildings that were acceptable and which
had been subjected to normal methods of
control) was within 13 mm. For 95% of walls
measured the verticality was within 10 mm.
It would therefore seem that the
partitions in the bungalow were not built
using normally acceptable building quality
standards.