A method is presented for predicting the amplitude bounds associated with the dynamic response of engineering structures with varying levels of parameter uncertainty. In particular, a novel SEA Extreme-Value-based bounding method is discussed and tested across the frequency range on a non-simple built-up structure with high and low-level random uncertainties. This method does not use expensive Monte-Carlo simulation and is therefore computationally very efficient. The paper shows that for a built-up structure, with both low and high-level uncertainty in a single parameter, the proposed SEA-EV-based prediction method compares extremely well at high frequency with FE-based Monte-Carlo simulation.