An extensive programme of research was conducted to make detailed measurements of the blast environment at different horizontal distances and heights above the ground behind a vertical cantileve blast wall when spherical charges were detonated at different heights above the ground and at different stand-off overpressures and peak specific side-on overpressures and peak side-on impulses obtained from the pressure-time histories were plotted in 'scaled space' that allowed a wide range of different terrorist threat scenarios to be represented. Comprehensive contour plots of overpressure and impulse behind the wall were developed. This information was then recast in the form of a series of design charts. These were accompanied by a simple and effective method of data extraction to provide engineers with information necessary to assist in the design for blast resistance of structures located behind the wall.