Agriculture Reference
In-Depth Information
With the numbered and prepared voussoirs stacked in order of use, the arch
would then be constructed, or 'turned', with the voussoirs dip-laid in numerical
order, working evenly, from either side of the opening; thus ensuring the turning
piece or centre was equally loaded. The turning of the arch would be finished
once the final, or 'key', brick at it's top, or middle, was placed. This key brick
had to be carefully dipped on either bed into the lime putty mortar and then
quickly lowered down tightly into position. Once turned, or completed, some
craftsmen asserted that it was best to very slightly 'ease' the turning piece or cen-
tre so that the bricks took up their bearing and locked tightly together, reducing
the possibility of a settlement crack when removing the support later. The inevi-
table small exussion of excess mortar from the face of the laid bed joints were
left untouched until they suitably stiffened; before being neatly trimmed flush
with the arch face. With all the joints full and true, some gauged arches were
made secure by filling joggle joints, cut or filed into the opposing voussoir beds
to create a channel, with a liquid hydraulic lime: sand grout. The final cleaning
of the arch face and soffit, by rubbing-up with the hand-held float stone, was
normally left until the arch face was dry and the whole building was completed.
When one is discussing gauged arches the straight or camber arch deserves an
individual mention. This arch was widely used yet was considered the most dif-
ficult to set out and construct correctly. Though highly favoured they were gen-
erally a weak form of construction, hence they were generally only a half-brick
in thickness with a timber lintel to the rear upon which was built a shaped brick
core to receive a segmental 'rough' relieving arch; its skewbacks above the ends
of the lintel. Camber arches were sometimes used over a large opening, how-
ever they were best limited to a span of 1.3 m (4 feet) as the centre could sag. In
essence this arch cannot truly be classed as an arch but as a scheme for spanning
an opening.
It is interesting to note that for the flat or straight arch, Neve (1726, 10) states:
Thefe Arches commonly confift of a stretcher, and a header in height, the stretch-
ers being a whole Brick's length, and the Headers a Brick's breadth.
Study of Batty Langley's own figures (Fig. 102), depicting the accurate bonding
of a façade and arch in his 1749 edition of
London Prices of Bricklayer's Materials
and Works
, show both straight arches not half-bonded, but quarter-bonded. The
stretchers are cut with dummy joints to create closers [quarter bricks to create
correct bond] next to the headers.
Generally aesthetic arch bonding followed the rules of the popular Flemish
bond at the quoin, with alternating courses of a stretcher and header in one
course, followed by header, closer and stretcher (a three-quarter bat on a
face height of four courses) in the next. Bond at the springing was normally
dictated by placing a stretcher in the lowest position at the centre or key on the
arch face, and working back to the first, or 'springing', bricks at the skewbacks.
