Evaluation of roof substrate retention properties under different moisture conditions

A laboratory analysis of the retention properties of a roof substrate focused on the initial moisture conditions of Bratislava roof substrate (low and moderate substrate moisture). The water retention capacity of the substrate was investigated by simulating a 15-minute rainfall event with intensities of 1.3 mm/min, 2.7 mm/min, and 3.8 mm/min. The effect of the depth of the substrate (7 and 10 cm) was also analysed. The results showed that a substrate with an initial moisture content of < 5% can retain a larger volume of runoff. It should be noted, however, that this analysis was for only one layer of a vegetated roof. To obtain more comprehensive results, it is necessary to carry out measurements in combination with all the relevant layers of a roof system that contribute significantly to the retention of runoff.