Well, I applied this material to the ceiling of a detached house on an island that had never been coated before, after first sanding it with a grinder fitted with sandpaper because it had "green spots." Since the roof had scratches and little dents, I first applied one diluted coat, and the next day I went up to brush the dents where the roller hadn’t managed to fill them in. I realized that, possibly because of the temperature (middle of summer, after all...), the material was still sticky and small flakes would come off when I left something on the roof. The photo was taken after only one coat had been applied, and I decided to apply the second one after 3-4 days to be on the safe side. After one coat on 40 sq.m and the next day the missing spots I mentioned, I had 1/4 of the barrel left; I will definitely need a second one, and I believe there will still be enough left to apply a third coat as well, even if it’s only partial! I can’t comment on waterproofing yet because that will show over time, but it does seem like there was a slight drop in the temperature inside the house! And I was surprised that in a second small barrel I was using with the material and a little water I had added, if I didn’t stir it every three minutes because of the heat, it would form a skin on top; in general, I think it dries quickly when left exposed! I am satisfied for now!