| |
|
It is recommended that a test
panel (ideally 2 square metres) be produced for inspection, and the
client, architect, main contractor, clerk of works etc. should not
allow work to commence until completely
satisfied with workmanship, texture quality, colour, depth of coat,
programme for plastering and scraping. |
|
This should not be part of the
main job and must be prepared well in advance to allow time for curing. |
|
Plasterers must become familiar
with the product’s water requirement, workability characteristics,
settingand hardening time which vary according to location, substrate,
temperature and humidity. |
|
50mm samples are provided on request
for colour indication only. |
|
A site sample panel is recommended
to ensure that the specifier is satisfied with the render colour and
texture. Sample panels available on request. |
|
WBS materials are manufactured from
natural products, and slight shade variations may occur. |
|
For WBS Scratch / Ashlar Effect / Brick
Effect Render: All areas must be scratched / scraped at the same stage
of readiness, as early scraping will result in darker shades, and
late scraping in lighter shades. A uniform approach is essential to
achieve an even finish. |
|
As the cement sets, lime is produced,
and this may come to the surface, causing some areas to exhibit an
opaque whitish layer. |
|
Render is most susceptible to lime
bloom in the early stages of setting, and therefore needs to be properly
protected from the weather and any other sources of water. |
|
Lime bloom is a temporary phenomenon,
and does not affect the durability or strength of the render. |
|
Suitably designed overhangs and flashings
should be provided to prevent water leakage on to the render. At ground
level it is recommended that the rendering should not bridge the DPC
to form a capillary path for rising damp. |
|
Cills and copings should project from
the face of the wall with an ample drip groove for their full length,
including through the mortar joints, to ensure that water is kept
clear of the render. Gutters and down-pipes must be designed with
the same intention. |
|
Angles may be formed using angle and
stop beads, stainless steel or PVC, or using chamfered battens. |
|
Plan ahead to avoid discontinuity in
any one area or walling which could lead to unsightly joints in the
rendering. |
|
Render expansion joints must follow
structural movement breaks. For other expansion joints refer to BS5262. |
APPLICATION
CONSIDERATIONS
|
|
Before any rendering begins, is it
is essential to ensure that the scaffolding enables suitable access
to the whole of the working face. |
|
When rendering on to a base coat, water
spray should be used to damp down walls prior to applying the final
coat. This will control suction between the two coats. |
|
WBS renders have a working temperature
range of 5°c - 35°c. |
|
During hot weather it is recommended
that work is started on the shady side of the building and continued
round following the sun. |
|
In cold weather, if frost is forecast,
work should stop in time to allow the material to set sufficiently
to prevent frost damage. Drying conditions will vary accordingly to
wind, temperature and humidity. |
|
Protection from rain and frost should
be provided for the first 48 hours after application. |
|
Do not render in cold damp weather. |
|
Do not permit down-pipes, sills, copings
and scaffold boards to throw water on to the setting render. |
|
Do not allow washings from quoins,
sills etc. to run on to the setting render. |
|
Render sacks, even with hoods, are
only shower-proof, and should be further protected to prevent damp
causing caking around the sack mouth. |
|
Shelf life is approximately one year
in dry conditions in original packaging. |
|
It is important to note that all WBS
renders are non-returnable. |
|
Home
Technical
Support
Fact
Sheet - WBS Cementitious Renders
WBS CEMENTITIOUS RENDERS - FACT SHEET
