An Introduction to the use of Lime
Many older properties can suffer from damp problems, cracking and hollow render. Before the 20th Century the building techniques and materials
used were very different from those used today. Traditional properties
need to be able to "breathe" to allow moisture within a solid wall
construction to evaporate from the external stonework or render.
Lime putty was the base product mainly used to produce mortar, plaster
and lime wash for traditional buildings. The advantages to using lime
putty mortars instead of cement based mortars is that they are porous,
thus allowing the property structure to breathe, they can accommodate
general movement and the self healing nature of lime products reduces
cracking problems. To repair and renovate using harder and impermeable
materials can often cause worse damp problems. Hard cement renders
and many masonry paints do not allow the moisture that is continuously
being drawn form the ground to evaporate easily to the outside. As a
result the building may suffer from cold walls, condensation , flaky paint,
rotten skirting boards and joists. A common mistake would result in the
building having chemical damp course injection, tanking or even being
dry lined - the "professional" has failed to understand the basic
requirements of a traditional property.
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In the 15th century. Oak and chestnut make particularly good riven
lath as they both contain natural oils, thus ensuring long life.
By the 19th century sawn lath started to be used, although there is no
doubt that riven lath is stronger, and its textured surface and exposed
grain affords a far better key.
Laths should be spaced about one centimetre (3/8") apart, Spacing can
be gauged simply by resting your little finger on top of the last lath to
get a sufficiently accurate gap - you seldom see a true craftsman with
a modern rule, measuring as he goes!) If the laths are fixed any closer,
the first coat (or 'scratch coat') of plaster will not be able to pass through
to form good nibs. Larger gaps will allow heavier nibs to form which are
liable to break off, filling the void behind the laths.
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Cob is an ancient building material, that has possibly been used for
onstruction since prehistoric times.
Cob structures can be found in a variety of climates across the globe;
In the UK it is most strongly associated with counties of Devon and
Cornwall in the West Country; Many old cob buildings can be found in
Africa, the Middle East, Wales, Devon, Ireland, Cornwall, Brittany and
some parts of the eastern United States. Traditionally, English cob was
made by mixing the clay-based subsoil with straw and water using oxen
to trample it. The earthen mixture was then ladled onto a stone
foundation incourses and trodden onto the wall by workers in a process
known as cobbing. The construction would progress according to the
time required for the prior course to dry. After drying, the walls would
be trimmed and the next course built, with lintels for later openings
such as doors and windows being placed as the wall takes shape.
The walls of a cob house were generally about 24 inches thick, and
windows were correspondingly deepset giving the homes a characteristic
internal appearance. The thick walls provided excellent thermal mass
which was easy to keep warm in winter and cool in summer. The
has a long life span even in rainy climates, provided a tall
foundation and large roof overhang are present.
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Pargeting is a decorative plastering applied to building walls. The
technique is largely confined to Eastanglia in England. Pargeting derives
from the word 'parget', a Middle English term that is probably derived
from the Old French 'pargeter' / 'parjeter', to throw about, or 'porgeter',
to roughcast a wall. However, the term is more usually applied only to
the decoration in relief of the plastering between the studwork on the
outside of half-timber houses, or sometimes covering the whole wall.
The devices were stamped on the wet plaster. This seems generally to
have been done by sticking a number of pins in a board in certain lines
or curves, and then pressing on the wet plaster in various directions,
so as to form geometrical figures.
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