Arches

THE ARCH IS SIGNIFICANT BECAUSE IT PROVIDES A STRUCTURE WHICH ELIMINATES TENSILE STRESSES IN SPANNING AN OPEN SPACE. WHEN THERE IS SUFFICIENT HEIGHT ABOVE A WINDOW, DOOR, OR ANY OTHER OPENING IN A BRICK WALL, A BRICK ARCH, EITHER CIRCULAR OR SEGMENTAL, IS USED TO SPAN THE OPENING, AND FORMS A VERY DURABLE AND EASILY CONSTRUCTED SUPPORT FOR THE WALL ABOVE. WHENEVER BRICK ARCHES ARE BUILT, GREAT CARE SHOULD BE TAKEN IN THEIR CONSTRUCTION, AND THEY SHOULD BE LAID WITH FULL MORTARJOINTS. IF THE SPAN IS MORE THAN 10 FEET, THE ARCH SHOULD BE LAID IN CEMENT MORTAR; IN FACT, IT IS THE BEST AND SAFEST TO LAY ALL BRICK ARCHES IN CEMENT MORTAR.
. WHEN SEMICIRCULAR ARCHES ARE CONSTRUCTED OF COMMON BRICK, THE BRICKS ARE LAID CLOSE TOGETHER ON THE INNER EDGE, OR INTRADOS, WITH WEDGE-SHAPED JOINTS ON THE OUTER EDGE, OR EXTRADOS; THAT IS TO SAY, THE MORTAR JOINTS ARE WIDER AT THE UPPER SURFACE OF THE BRICK RING THAN AT THE LOWER SURFACE, SO THAT THERE IS MORE MORTAR AT THE TOP OF THE JOINT THAN AT THE BOTTOM. THE BED SURFACES OF THE BRICK ARE THEREFORE NOT ON RADIAL LINES, AS THEY ARE IN A GAUGED BRICK ARCH, BUT THE RADIAL LINES ARE ASSUMED TO PASS THROUGH THE CENTER OF EACH MORTAR JOINT.
SHOWS A SEMICIRCULAR ARCH CONSISTING OF FOUR ROWLOCK COURSES OF BRICK. THESE ARCH BRICK ARE ALL LAID AS HEADERS, AND SHOW AN 8-INCH REVEAL ON THE UNDER SIDE OR SOFFIT OF THE ARCH. ARCHES BUILT IN THIS WAY, OF A SERIES OF ROWLOCKS OR CONCENTRIC RINGS, HAVE NO CONNECTION BETWEEN THE RINGS OTHER THAN THAT AFFORDED BY THE ADHESION OF THE