The floor may span up to 9 metres and incorporates permanent soffit forms (10) of a precast lightweight cellular insulating concrete construction. The soffit forms (10) may be made by injecting a rigid foam into ordinary concrete, having a density of between 300 and 600 kg per cubic metre, and constituting beam or slab elements of which the transverse profile accommodates a traditional reinforced concrete beam (11) and slab (12) floor. Once the units (10) are placed tensile reinforcement may be positioned in rectangular section beam-forming channels (11) together with latticework web reinforcement (16). Next horizontal mesh slab steel (16A) is positioned and finally the concrete is poured. A soffit liner (S) e.g. plaster may be cast on at the factory, and the slab element (12) of the over floor may be similarly treated, the casting being effected on tables with edge upstands.
<P>ELEMENT COMPOSITE EN BETON AUTOPORTANT SOUS FORME DE HOURDIS ET PROCEDE POUR SA FABRICATION.</P><P>L'ELEMENT EST CONSTITUE D'UN BETON ISOLANT LEGER 10 DANS LEQUEL A ETE COULE UN BETON LOURD CLASSIQUE 12. LE BETON LEGER EST DE PREFERENCE POURVU DE GORGES ET LE BETON LOURD DE PREFERENCE ARME, FORME AVANTAGEUSEMENT UNE DALLE NERVUREE.</P><P>APPLICATION A LA REALISATION DE HOURDIS ET AUTRES ELEMENTS DE CONSTRUCTION.</P>