After pouring the reinforced concrete beam behind the lintel, the next challenge was to tackle the relieving arch over the three light window. This was, primarily, intended to be an architectural feature, but, being properly constructed it transfers the weight from the wall above outwards to the sides of the opening.
The first step was to lay the skew backs and position the infill, this needed to have the right curvature to maintain a neat joint with the intrados. I drew the profiles full size on some old masonite and cut out a template, seen in the above picture. With these in place, I then built up the walls on either side to ensure the arch had lateral support.
The voussoirs in place, ready for me to cut and lay the fiddly, wedged shaped blocks on top of them.
To support the first floor bearers, corbels are positioned in the stonework, these, to my inconvenience, needed to be formed in the backs of the arch. Alternate voussoirs were cut in 2 separate pieces to allow me to form the corbels on the back half, another tricky job, getting the angles right.
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