La pedra en sec. Materials, eines i tècniques tradicionals a les illes ...

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* * *: 5 5.7 THE WORK
Definition
To place the rows of stone which
make up the facing so that they are
tightly bound and make the wall solid.
Description
The way of laying stones varies a lot
depending on places and from one
wall to another. Traditionally the quality
and characteristics of the bond
have been attributed to the master
mason, to the existence of local
schools, or to the characteristics of
the stones. At first sight this seems to
be true, but fashions have to be taken
into account, as the same type of
bond has not always been held to be
the correct one, along with the
amount of money spent and the prestige
of the owner or, in the case of
public works on the engineer.
Generally speaking the relationship
between the external appearance and
the solidity of a wall is not a direct
one. Nevertheless, master drystone
masons agree on that the placing of
the stones (not only the external
appearance) is an essential principle
in the strength of the wall. Based on
this a series of recommendations
about laying the stones have been
given, even though as it can be seen
below these are not always followed
in real life:
1) Stones must be laid in an orderly
fashion, placing the largest at the bottom.
This is generally done when the
terrace wall is built on a previous collapsed
section or as part of specially
planned work. This is not always the
case in less well-made terrace walls
built on a slope in which the stones
can be laid in the wall as they are
taken out.
2) They should be arranged so that
the vertical joints do not fall directly
one above the other, that is to say so
m~tm~r~~r@no columns.
3) They should be wedged on the inside
and never on the outside which
would not offer any resistance to
movement in the event of upward
thrusts. In spite of this recommendation,
exceptional cases can be found
with smaller stones placed between
bigger ones in some facings although
they are not intended to wedge them
in place.
4) They should be placed so that their
contact surface is as large as possible,
thus increasing friction and resistance
to movement and hence stability.
5) They should be as large as possible
so that the terrace walls are held
up by their own weight.
It is difficult to establish clear differences
between types of bonds in terms
of the layout of the stones and on the
ways in which they are worked and
therefore on the external appearance
of the wall. In popular terms, a distinction
is made between old or rustic
bonds, defined as those made with
irregular-shaped stones which have
not been dressed and are not properly
fitted together leaving wide gaps
between the stones. The tip dressed
bond distinction is made when the
stones are dressed with the tip of the
hammer, and are laid in an orderly
way in rows; and the polygonal bond,
which is common on roads built at the
end of the 19th century, where the stones
are laid in polygonal figures and
with very close fitting joints.
Cataloguing of cultivated terrace
fields in Majorca has led to the establishment
of a descriptive terminology
in order to be able to differentiate between
bonds. A distinction in the
degree of dressing of the stones is
made between the following:
. Rustic, old or non-dressed bond:
there are no obvious signs on the stones
having been dressed with a ham-