Refractory roof construction for the heating chamber of an industrial furnace

In a refractory construction for the roof of an elongated heating chamber of an industrial furnace, said chamber having vertical side walls on each side of said chamber, the combination of a plurality of transverse rafters extending across said chamber and spaced from each other longitudinally along said chamber, each rafter comprising a pair of arch bricks, each sloping upwardly toward the longitudinal centerline of said chamber, each of said arch bricks having an outer end engaging and held by its respective side wall, said arch bricks having inner ends adjacent said centerline, an arch key brick for each rafter located between said inner ends of its respective arch bricks and engaged thereby, and a plurality of roof bricks extending longitudinally of said chamber between successive rafters, said roof bricks having ends resting on and supported by the pair of rafters between which it extends, said roof bricks having an outer one on each side of said chamber, said arch key brick has a top surface which with the inner ends of said arch bricks define a first horizontal surface and there is a notch in the upper surface of each outer roof brick adjacent said first horizontal surface which defines a second horizontal surface lower than said first horizontal surface.