ISO 9836 pdf download Performance standards in building — Defnition and calculation of area and space indicators 5.1.4Ilntra-muros area 5.1.4.1 The intra-muros area is the total floor area (5.1.3) less the floor area taken up by the external walls(floor area of the building envelope). 5.1.4.2 The intra-muros area is determined separately for each floor level. The calculation principlesestablished for the...