There is a widely held view within the construction industry that the procedures currently used in design tend to overestimate actual prop loads. The main aim of the research was to investigate the reasons for this apparent discrepancy by monitoring the temporary prop loads at Canada Water and Canary Wharf. Prop temperatures were also measured to assess their influence on prop loads. This publication, being a research summary, should be a help to temporary works designers and geotechnical engineers. It accompanies CIRIA publication C517.