Civil Engineering Reference
In-Depth Information
normally achieved from the best
natural slates, premature
deterioration can happen with all
kinds of slating materials.
Stability of colour may be a
problem, although it is not thought to
be widespread; distortion and
cracking are more common but not in
all products. Some slates may lose
their surface coating but this is
relatively rare in BRE's experience.
Work on site
Storage and handling of materials
See the relevant sections in
Roofs and
roofing
.
Figure 9.5
Tile hanging in progress on a housing site. Unfortunately the 'breather' membrane is not a
breather membrane at all, but is a polyethylene sheet. This forms a vapour control layer on
the cold side of the thermal insulation, and there is therefore a risk of condensation inside
the polyethylene. There should be toe boards on the scaffolding
Workmanship
Tiling
Adequacy of the bedding and
grouting is of prime importance
(Figure 9.7), together with providing
sufficient movement joints.
Weathertightness, dampness and
condensation
Tiling
As with any comparatively
impervious finish which is prone to
cracking, the weathertightness of the
wall will depend on the avoidance of
cracks which allow rain water run-off
to penetrate behind the finish. Once
behind, it may not easily find a way
out, and frost action can then occur.
Durability
Tiling
Provided the tiles are suitable for use
externally, durability depends for the
most part on the provision of suitable
movement joints (see the case study
opposite) to overcome any
differential movements between tile
and substrate, and on the integrity of
the adhesive
(230)
and grouting.
Tile and slate hanging
As with roofs, in replacement work it
could be advantageous to use nails of
aluminium, austenitic stainless steel,
copper or silicon bronze
(BS 1202-2
(231)
and 1202-3
(232)
). Nails
of steel (whether galvanised or not),
aluminium or copper alloys should
not be used where battens have been
treated with CCA (copper-chromium-
arsenic) preservatives.
Tile and slate hanging
Tile or slate hanging may be found
with corroded nailing and there may
be rot in any supporting battens.
(For the durability of the slates and
tiles themselves, see
Roofs and
roofing
.) The fact that tiles are laid
almost vertically does not make them
immune to biological growths. While
in many cases growths may
be thought desirable, removal by
application of surface biocides will
often enhance the durability of the
material.
Man-made slates are available in a
very wide range of materials - for
example fibre reinforced cements and
fillers such as natural slate bound
with resins - and it is therefore not
possible to give universally
applicable guidance on the durability
to be expected. Although shorter
lifespans can be expected than are
Tile and slate hanging
Provided the tiling or slating is
constructed without obvious faults,
the wall should be weathertight for all
exposures of driving rain, although
wind damage may lift tiles or slates,
as with roofing. A suitable breather
membrane (Figure 9.5) to BS
4016
(229)
is important. See also
Roofs
and roofing
.
Inspection
The problems to look for in ceramic tiled
walls are:
◊
tiles cracked or broken due to substrate
movements or vandalism
◊
tiles loose due to adhesive failure
◊
sulfate attack in substrates
◊
tiles deteriorating, being not suitable for
exposure of site
◊
no movement joints where required
Fire
Ceramic and concrete tiles, and
natural and artificial slates, are all
suitable for use adjacent to
boundaries.
The problems to look for in slated and tile
hung walls are:
◊
slates or tiles broken, missing or
delaminating
◊
tile nibs broken
◊
slates or tiles incorrectly fixed
◊
nails which have corroded
◊
flashings missing or damaged
◊
flashings too thin for durability
◊
snow or rain penetration
