Not being lazy butthe existing felt on my shed has been there 15 years! No sign of rips or holes and I just finished cleaning FOUR large bucketfuls of moss from it :-) I just wonder if I should replace all the felt "just in case"? And if so whether to leave the existing felt in place? I guess nailing through new felt I could end up landing on top of the old clout nails. There's also the matter of extra weight - surprising how heavy that stuff is isn't it. Oh .... it raining again - so not a job for today anyway.