Impact actions generated by storm debris including hailstones have been causing very costly damage to building envelopes, including metal and tiled roofs, aluminium facades and glazing panels in regions of temperate climates. Few guidelines for assessing the vulnerability of existing installations have been developed. At present, the performance of these installations in response to impact action is normally determined either by : (i) costly pass/fail prototype experiments; (ii) numerical simulations which are common but never adequately validated by physical experimentations; or by (iii) over simplified calculations based on treating the impact action as an equivalent static force. There is a lack of integrated use of analytical tools in conjunction with experimentation techniques for accurately quantifying the effects of solid object impact. An impact action can be resolved into the localised contact force and the global deflection demand of the impact. The amount of contact force generated by the impact is a critical piece of information as it controls localised damage to metal claddings in the form of denting, or perforation. Accurate measurement of contact force generated by windborne debris and hailstones is now possible by virtue of the experimental device that was custom built by the authors. Impact test data so obtained has been leveraged for the calibration of analytical models in order that design charts providing estimates of impact forces can be produced. This paper presents analytical and experimental techniques that have been used by the authors in determining the forcing functions of a pre-defined impact scenario. The predicted forcing functions can be applied quasi-statically to aluminium specimens for the assessment of damage that are caused by the impact of a range of storm debris.