Roundtower Lime A Guide To Internal Lime Plastering | Página 4

TECHNIQUES OF HYDRAULIC LIME
PLASTERING
The techniques employed in the this coat is applied in a coat of
application of hydraulic lime plasters approximately 10mm thickness, this coat
should be to ensure a correct bonding with can be applied by use of a steel trowel or
the background while striving to minimise thrown onto the wall by use of a harling
shrinkage and rapid drying, these trowel and then flattened in by the steel
techniques should be followed throughout trowel. When this coat has firmed up but
the plastering process. Lime plastering is has not gone hard, the plaster is keyed or
generally applied in 3 coats, but it is scratched up to produce a key for the
common to find 2 coats or even single coat following coats. The keying up is carried
work in vernacular or early structures. In 3 out by use of a lath scratcher or similar
coat work the first coat on masonry or toothed instrument and care should be
brickwork is generally known as the scratch taken not to cut through the plaster coat
coat or render coat, back to the background.
The keying up is generally in the shape of diamonds of approximately 30mm spacing. This
coat should be allowed to harden for 72 hours minimum before further coat of plaster are
applied, before applying the second coat the first coat should be checked for shrinkage
cracks, and these should be filled with plaster before proceeding with further coats, before
the second coat is applied the first coat should be brushed down to remove any dust which
may have blown onto the surface. The first coat should then be damped down to ensure that
the second coat is applied to a damp but not wet surface. This second coat is called the
floating coat and is the coat which is straightened to ensure a flat and even surface, after this
coat has been straightened, the surface of this coat is scoured up with a timber or
polyurethane float (rubbing up with a float similar to finning up render).
The purpose of the scouring is to compact the plaster and counteract shrinkage. This process
is generally required to be carried out at least twice, during the scouring up, any small holes
should be filled before the finishing coat is applied. This coat should also be allowed to dry
and harden for 72 hours before applying the final coat.After once again damping down the
floating coat, the final coat is applied. This coat known as the setting coat, is applied in two
layers, coat on coat, with the trowel. This coat is applied in a way similar to skimming. This
material should be of a wet enough consistency to allow along and even spread. Once the
setting has been applied, it is scoured in a similar manner as the floating, to counter-act
shrinkage and then the surface can be left with a rubbed up rendered type finish or polished
smooth with a steel trowel.