Progressing the rights to light debate Part 2: the grumble point revisited

摘要

Purpose - The paper examines the origins of the so-called "grumble point" (a sky factor of 0.2 per cent) as the measure of daylight adequacy in rights to light disputes. It seeks to identify the rationale, and underlying scientific basis, for the adoption of this standard in the early twentieth century. Design/methodology/approach - Analysis of archive materials. Findings - The use of the 0.2 per cent standard does not appear to be based on empirical investigations involving human perceptions of adequate light. No evidence exists of the investigations reputedly undertaken by Percy Waldram during the early twentieth century. Waldram's own writings suggest that the standard began as a "rule of thumb" and was only later justified by reference to other independent reports. These generally do not support the use of the standard and, in any event, were soon superseded by other reports that concluded that it was too low. There is a lack of reliable evidence to justify the original adoption of the 0.2 per cent figure, and many of the assumptions underpinning modern rights to light practice are found to be based on inaccurate information. Research limitations/implications - Continues the debate, started in this journal in 2000, about the future of surveying practice in rights to light disputes. Practical implications - Places new information in the public domain which has implications for the professional liability of surveyors advising clients in rights to light cases. Originality/value - Presents the first investigation into the original scientific basis for modern rights to light practice since its introduction in the early part of the twentieth century.