Formation of a reinforced concrete floor joist or lintel placed in the "U" blocks made by autoclaved cellular concrete realized by milling mattONE 500 blocks, having thermal conductivity λ10 dry equal to 0.12 W / mK and CE marking in compliance with UNI EN 771 -4, reaction to fire in Euroclass A1, dimensions 20, 24, 30, 36, 40, 45, 50 cm x 25 x 62.5 cm (S x H x L), section size for the casting CLS sp20cm 10 cm x 17.5 cm - other thicknesses 15 cm x 17.5 cm (B x H) (reinforcement calculations and checks to be carried out).