Agriculture Reference
In-Depth Information
Figure 147
The re-rubbed gauged
arch, dry-bonded in
position and with
the profile trees
erected and set-out
ready for rebuilding
to commence, 1998.
(Courtesy of Richard
Keech)
and this technique was repeated on the soffit marks of the arch centre. With all
voussoirs ready for re-laying they were dry-bonded on top of the centre, using
cut lengths of dpc to space out the 1 mm joints; yet another technique learned
from Bedford College (Fig. 147). A check was made to make sure that the top
of the key bricks lined through precisely horizontally to facilitate a standard
bed joint to the underside of the Platt band. Satisfied that all our setting out
and preparations were sound the dry-bonded arch was then disassembled and
laid out in the order of laying onto the elevated bench ready for laying.
Two horizontal lines maintained the arch face to the surrounding brickwork
during re-building, one positioned near the bottom of the arch, the second
just down from the crown, to prevent the arch twisting across the opening. Two
further lines from the profile trees to the striking point guided the radial pos-
itions of each voussoir correctly.
We soaked the porous 'cutters' in water, to a point just short of saturation,
reducing their suction, giving additional time to position them and improv-
ing the overall bond strength. The laying mix for the arch was prepared using
matured slaked lime putty passed through a fine-meshed screen and then
mixed with silver sand with just a drop of boiled linseed oil. All of these ingre-
dients were mixed by hand-whisk until a smooth, creamy, consistency was
obtained, and then placed into a dampened 'dipping box'.
The laying process itself was simply a matter of giving each voussoir another
quick dip, or 'dock', into the bucket of water, waiting for any residual surface
water to run off, and then carefully dipping the voussoir into the prepared lime
putty mix within the dampened dipping box. Great care is taken dipping vous-
soirs to make sure that only the bed of the brick takes-up the joint and none
rides-up and over the arrises staining brick faces. A small leaf towel helped
'ease' the mortar forward and tight up to the face arris. The voussoir was then
carefully laid into position and radial line on the arch centre using a very small
