Arch structure defining equidistant points along a radial curve and comprising uniformly-sized, standard stock, elongated rectangular cross-section stringer members, uniformly-sized, standard stock, elongated rectangular cross-section arch members each having a midpoint and first and second angled ends of equal but opposing to one another angular magnitude, each arch member adapted to converge crossways on and completely abut a side surface of two non-adjacently positioned stringer members, each of the arch members further being adapted for undergirding a stringer member located between two non-adjacently positioned stringer members at the mid-point of the arch member, each arch member adapted for being oriented in scissor-like crossing relationship to another arch member, a plurality of fasteners, and where needed at least one tensioning member preferably attached between end stringer members, or alternatively between foundation members, the tensioning members and fasteners making the arch structure fortified to be as if monolithic.