All of the masonry and structural work was designed in accordance with recognized city building code requirements and the recommendations of the American Institute of Steel Construction and the Concrete Reinforcing Steel Institute. All of the concrete and steel work was designed to carry from three and one half to four times the load assumed.
The assumed loads exclusive of the dead loads are as follows: for the roof, thirty pounds per square foot; for the auditorium and balcony, seventy-five pounds per square foot. Considering the factor of safety used in the design and the fact that the roof trusses and concrete slab are heavier than theoretically necessary, it would probably require a depth of water of from two to three feet or a depth of from five to six feet of fairly wet snow to cause the roof to fail.
It is a recognized fact that concrete increases in strength with age. It is customary to design concrete on a basis of its receiving its full load at an age of one month. After that time it continues to increase in strength, and after several years it has probably twice the strength for which it was designed. A relatively dry mixture of concrete insures much greater strength, and every effort was made to see that too much water was not used in the mixtures. When knots and grains of the form lumber show on the finished work, it is a good indication of strong concrete. If the concrete roof slab is examined from below, there is almost an illusion that wood has been used rather than concrete.
Buildings usually receive their most severe loads during consctruction, and this is particularly true of theatres on account of the high scaffolding and the piles of heavy material, which are not usually uniformly distributed.
It can be safely stated that the Lyric building has been designed, from a structural standpoint, equally as conservatively as many large city theatres, such as the American in Roanoke, which was handled by the same firm of architects.