This is one of the most important trades as it provides
both the finishing standard to the interior of your
new home and, where the outside is rendered, provides
the final weathering coat.
Internally the choice, for self builders, is
whether to opt for hard plaster (a sand and cement render
coat with smooth plaster finish) or dry lining (a plasterboard
finish). In the past this choice was often dictated by whether
the home was built using traditional masonry construction
or was timber framed. Timber framed
properties can only be dry lined but those using building
traditional masonry construction have the choice and increasingly,
they are opting for dry lining.
Key Points
1
If you opt for hard plaster,
don't forget to give plenty of time to dry out naturally
before decorating
2
Remember
that bagged plaster has a limited shelf life. Don't
buy or use old plaster.
3
No
amount of paint or wallpapering will cover bad plastering
- choose your contractor with care.
4
Don't
forget that the plasterer will need a foot scaffold
for setting ceilings.
5
If you are rendering the
ourside, use an independant rather than a putlog scaffold
Hard plaster requires one, sometimes two coats of sand
and cement render with a finishing coat of smooth plaster.
The sand and cement render can be replaced by proprietary
plasters of differing types, each one of which is formulated
for use a different substrate. The advantage of hard plaster
is that it is extremely durable. The principal disadvantage
is that it puts enormous amounts of water into the structure
and this can lead to long drying out times.
Dry Lining
Dry lining uses plasterboard fixed to the walls and is
therefore a relatively dry process, which can be decorated
shortly after completion. With a timber framed home the plasterboard
is tacked directly to the timber studs. When used in traditional
masonry construction, it can either be stuck to the walls
by means of dabs of plaster or tacked to battening, firmly
fixed to the substrate. Dry lining can be taped and jointed
using special paper tape or it can be skim coated with a thin
coat of plaster to provide a surface finish that is indistinguishable
from hard plaster.
The standard plasterboard can be replaced by the more durable
Gypsum Fibre Boards, which provide greater sound insulation
properties and are strong enough to take fixings directly.
Ceilings
Ceilings to be Artexed are usually tacked with plasterboard
and taped with paper scrim prior to the finish being applied
from the floor using special applicators and patterning tools.
Any decorative mouldings or covings are put up before the
Artex
is applied.
Plastered, or ‘set', ceilings are jointed with a silk
scrim and then finished with a thin coat of smooth plaster.
This is applied by a hand held trowel and there is therefore
the need for a ‘board or foot scaffold'. Any decorative
mouldings or covings are put up afterwards.
Floor Screeds
If a floor is to be screeded it is the job of the plasterer.
A screed can be mixed on site from sharp sand and cement or
it can be brought in ready mixed in truck loads. Screeds that
are bonded directly onto an oversite or concrete base can
be as thin as 50mm. Those that are laid on top of insulation
have to have a minimum thickness of 65mm. Screeded garage
floors have to have reinforcement mesh within them.
Floor Screeds
It is also the plasterer's job to render the outside of
a building. This means that an independent scaffold should
be employed if you are not to incur heavy charges for moving
and altering the scaffold.
Rendering is normally carried out with a one or two, occasionally
three, coat render of sand and cement. For a smooth finish,
the final coat is rubbed up with a float or trowel. Pebbledash
is created by thickening the final coat and then dashing (throwing)
pebbles into the mixture and pushing them home with a trowel.
Tyrolean is created by a hand held machine that dashes a mixture
of pebbles and render onto a first coat of render.