The experimental scaling properties of the first flux penetration in a disordered superconductor (critical exponent psi = 2.7) are derived from a granular fractal model. It assumes localisation of the order parameter in randomly coupled regions and a temperature dependent cutoff in the couplings. Screening currents circulate in percolation fractal clusters with temperature dependent percolation parameter. Their description requires the heuristic transposition of classical calculations of first penetration fields in superconductors into fractal space.