This paper present the results of combined bending and shear test on composite slabs reinforced with steel fibres in-situ concrete topping. The mechanical properties of steel fibre reinforced concretes (SFRCs) were first determined by varying the fibre dosage from 0% to 1.25%. The result shows that there was not much improvement on the SFRC properties for volume fraction of steel fibre (Vf) of between 1.0% and 1.25%. Following this, SFRC with Vf = 1.0% was chosen and cast onto the precast slab. In addition to this, the top of the precast slab was prepared with four (4) different surface roughness i.e. smooth as-cast, roughened in the longitudinal and transverse direction, and exposed aggregate. The SFRC replaced the conventional method of using cast in-situ reinforced concrete as structural topping. The experimental results on its ultimate shear capacity were further compared with the parametric equation proposed in this paper using SFRC as concrete topping. The result shows that the ultimate shear capacity was 4% and 6% lower than the calculated value for the exposed aggregate and longitudinal roughened surface, respectively. For the smooth as-cast and transverse roughened surface, they were even 28% and 24% kN lower than the calculated value. Further comparison with previous researcher also found that the ultimate shear capacity for specimens with SFRC topping (except for the exposed aggregate surface) was 10% to 37% lower than the conventional (plain) ones. The finding also suggests that surface roughened in the longitudinal direction was better than the other surface textures using SFRC as topping in terms of interface bonding.