Among the preprocessing steps of a sparse direct solver, reordering and block symbolic factorization are two major steps to reach a suitable granularity for BLAS kernels efficiency and runtime management. In this talk, we present a reordering strategy to increase off-diagonal block sizes. It enhances BLAS kernels and allows to handle larger tasks, reducing runtime overhead. Finally, we will comment the resulting gain in the PaStiX solver implemented over StarPU and PaRSEC.