With the increase of terrorist attacks over the past decades, many engineering societies have started issuing design guides to calculate blast loads on structures. While such guides can be successfully used to assess blast loads due to single detonations, the effects of multiple detonations are often overlooked. In this research, the enhancement in blast parameters resulting from simultaneously detonating multiple charges is investigated, emphasising the interaction of blast waves with narrow targets. A parametric CFD study using the finite volume code Viper::Blast was performed where the number of charges, their arrangement, and the scaled stand-off distances were changed. It is found that, when detonated simultaneously, multiple charges return much higher pressure and impulse values compared to an equivalent single charge. Moreover, an arced arrangement of multiple charges is more efficient than a flat arrangement in enhancing blast wave parameters. Such enhancement is beneficial in scenarios involving demolition. Approximate methods to compute blast wave parameters from multiple simultaneously detonated spherical charges are presented in this study, where pressure and impulse from multiple charges can be computed by only knowing the parameters resulting from an equivalent single charge.