Corrosion attacks steel buildings mainly when the connections wait for welding on site. In the companion paper, the effects were investigated by a series of weld tests. The results show that the surface rust may increase the level of porosity in steel welds, reducing the strength by 5% on average. This paper made a case study, further investigating the effects together with those of workmanship. The seismic risk of the example building has been assessed and compared in detail for acceptable and marginal quality workmanship. The results obtained from the above studies will help develop more sound strategies in construction management and building renovation.