Mullion wall

A mullion wall (also known as H-frames^[1]) is a structural system in which the load of the floor slab is taken by prefabricated panels around the perimeter. Visually, the effect is similar to the stone-mullioned windows of Perpendicular Gothic or Elizabethan architecture. Mullion wall concept was first developed by the engineer Felix Samuely^[2] in the 1940s to avoid problems with routing the service runs around the joins of columns and beams.^[1] The column pairs with beam in between forming the H are staggered from floor to floor. With floor beams attached to the horizontal part of the H, space on the inside of columns is free to run drainage, etc.^[3]

The technology was used by George Grenfell Baines together with Felix Samuely in order to cope with material shortages at the Thomas Linacre School in Wigan (1952).^{[citation needed]} It was refined at the Shell Offices in Stanlow (1956), the Derby Colleges of Technology and Art (1956–1964),^[4] and Manchester University's Humanities Building (1961–1967).^[5]

While not widely used,^[1] a mullion wall approach was adopted by Eero Saarinen at the US Embassy, London (1955–1960)^[2] and by Minoru Yamasaki at the World Trade Center, New York (1966–1973).

The staggered layout of the mullion wall creates a checkered look of the facade, frequently accentuated by two-tone paint job, following the maxim "if you cannot be sure of hiding it, emphasise it."^[3]